Attention Valued Visitor: A Drug Reference Page for FDA Approved General Anesthetics is now available!
Shawn Thomas (Shawn@neurotransmitter.net) is working to summarize the mechanisms of action of every drug approved by the FDA for a brain- related condition. In addition, new pages with more automated content will soon replace some of the older pages on the web site. If you have suggestions about content that you would like to see, e-mail Shawn@neurotransmitter.net if you have anything at all to share.

[Above Figure from Gary Cziko's Home Page]

This page is a compilation of information about how humans might control their perceptions. Information on perceptual control theory (PCT) is included to provide a realistic psychological perspective on neuroscience research. According to perceptual control theory, behavior is the control of perception rather than the response to a stimulus. Research involving various types of control systems that can be found in the brain is included on this page to demonstrate that control systems are not solely in the domain of engineers. If the concepts of homeostasis and homeorhesis may be applied to internal environments, can they not also be applied to the external environment of an organism? The brain is a means toward transferring perceptual signals derived from the external environment into the internal environment of billions of interconnected neurons. Control systems within the brain and body are responsible for keeping perceptual signals within survivable limits, regardless of the nature of the environment that they are derived from. By integrating perceptual control theory with research from the field of neuroscience, the future of human self-awareness might be realized by individuals willing to do so.

Mansell W.
Control theory and psychopathology: an integrative approach.
Psychol Psychother. 2005 Jun;78(Pt 2):141-78.
Perceptual control theory (PCT; Powers, 1973) is presented and adapted as a framework to understand the causes, maintenance, and treatment of psychological disorders. PCT provides dynamic, working models based on the principle that goal-directed activity arises from a hierarchy of negative feedback loops that control perception through control of the environment. The theory proposes that psychological distress arises from the unresolved conflict between goals. The present paper integrates PCT, control theory, and self-regulatory approaches to psychopathology and psychotherapy and recent empirical findings, particularly in the field of cognitive therapy. The approach aims to offer fresh insights into the role of goal conflict, automatic processes, imagery, perceptual distortion, and loss of control in psychological disorders. Implications for psychological therapy are discussed, including an integration of the existing work on the assessment of control profiles and the use of assertive versus yielding modes of control. [Abstract]

Vancouver JB.
The depth of history and explanation as benefit and bane for psychological control theories.
J Appl Psychol. 2005 Jan;90(1):38-52.
A longstanding debate has recently re-erupted in the self-regulation literature around the concept of self-efficacy. This article presents an argument that the debate emerges from a lack of understanding of the history of control theories within both the social and physical sciences and the various levels of explanation to which phenomena can be subjected. This history, coupled with the issues of determinism, materialism, and empiricism evoked by the deeper level of explanation that some versions of control theory provide, has led some critics to mis-apply non-psychological properties to control theories and obscure their usefulness. Here, the usefulness of a deeper control theory level of explanation is illustrated using comparisons with explanations found in goal-setting theory and social cognitive theory. [Abstract] [Full Text]

Marken RS.
Controlled variables: psychology as the center fielder views it.
Am J Psychol 2001 Summer;114(2):259-81
"Perceptual control theory (PCT) views behavior as the control of perception. The central explanatory concept in PCT is the controlled variable, which is a perceived aspect of the environment that is brought to and maintained in states specified by the organism. According to PCT, understanding behavior is a matter of discovering the variables that organisms control. But the possible existence of controlled variables has been largely ignored in the behavioral sciences. One notable exception occurs in the study of how baseball outfielders catch fly balls. In these studies it is taken for granted that the fielder gets to the ball by controlling some visual aspect of the ball's movement. This article describes the concept of a controlled variable in the context of research on fly ball catching behavior and shows how this concept can contribute to our understanding of behavior in general." [Abstract]

Richard S. Marken
Looking at behavior through control theory glasses
Review of General Psychology, 6(3):260-270 2002
"Behavior is always seen through the theoretical preferences of the observer. These preferences act like different prescriptions for glasses. The most popular glasses use the causal theory prescription, through which an organism's behavior appears to be the result of external or internal causes. This article describes glasses that use the less familiar control theory prescription, through which behavior looks like the organism's purposeful efforts to control its own perceptions. The consequences of looking at the same behavior through these different "glasses" are demonstrated by comparing examples of real-life behavior with the behavior of computer simulations available on the Internet. A method is described that makes it possible to determine which "glasses" provide the best view of any particular example of behavior."

Richard S. Marken
Fielder’s Choice: A Unified Theory of Catching Fly Balls
"A closed loop exists when the way a system acts influences what it perceives while what it perceives is influencing the way it acts. The fielder’s path choice occurs in a closed loop because the way fielders act (the path chosen) influences what they perceive (the fly ball) while what they perceive is influencing the way they act. When behavior occurs in a closed loop, the behaving system is acting as a control system and the appropriate theoretical framework for understanding the system’s behavior is control theory. Control theory shows that the behavior of a control system (such as a fielder) must be understood as a process of controlling perception rather than choosing action (Powers, 1973).

A control system acts to bring a perception of some aspect of its environment to a predetermined or reference state while protecting it from the effects of disturbance. This process is called control and the perception that is brought to and maintained in the reference state is called a controlled variable (Powers, 1978). The actions that protect the controlled variable from disturbance are driven by error -- the difference between the reference and actual state of the controlled variable -- not by information about the disturbance itself. So the actions of a control system depend on (often invisible) disturbances to the controlled variable, not on information regarding the actions to be taken to deal with those disturbances. From a control theory perspective, therefore, a unified fielder theory must account for the perceptions a fielder chooses to control rather than the path the fielder chooses to take." [Full Text PDF]

Control Systems Group

Responsible Thinking Process
(Includes several good articles about PCT)

PERCEPTUAL CONTROL THEORY (PCT):
Basic Models (Includes a nice control system diagram)

Bruce Abbott's PCT Site

Gary Cziko's Home Page

Gary Cziko
Without Miracles: Universal Selection Theory and the Second Darwinian Revolution
"But of most importance for our purposes, the theory provides a plausible explanation for how behavior can become and remain adaptedly complex. It is clearly not the case, as believed by Darwin and Lorenz, that organisms with useful fixed behaviors are selected during the course of evolution, resulting in innate, fixed patterns of behavior known as instincts. And it is also not the case that specific behaviors are selected by the environment by contingencies of reward during the life of the organism, as believed by Thorndike and Skinner. It is the selection of organisms with useful, adapted perceptual control systems over the course of evolution, coupled with the organism's cumulative variation and election of its own perceptual control systems during its relatively brief life, that accounts for the adapted nature of behavior. There is no instruction by the environment, no stamping in of stimulus-response connections within the nervous system. Rather, we find a very Darwinian process of selection, not of behaviors, but of closed, negative-feedback loops encompassing perception, comparison with the reference level, and action, which allow patterns of behavior to remain functional, not only from one occasion to the next, but also within the continually changing environment of the behavior itself.

What may seem mysteriously ironic in all this is to realize that the purposeless process of natural selection has led to the evolution of purposeful organisms. But the irony fades when one considers the great survival and reproductive advantages of organisms that are able consistently to achieve goals essential to their survival and reproduction despite an unpredictable, uncaring, and often hostile environment." [Book Link]

Gary Cziko
The Things We Do Using the Lessons of Bernard and Darwin to Understand the What, How, and Why of Our Behavior
"The basic Darwinian lesson informs us that our evolutionary past provided
us and all animals with certain basic preferences. We prefer certain
foods, odors, and tastes and are repulsed by others. We prefer environments
that are not too hot and not too cold. We look for certain characteristics
in mates, which differ depending on our sex. We do what we can
to assist the well-being of our children, close relatives, and other individuals
from whom we can expect such assistance in return. We prefer the
company of family members and others who are most like us, and are wary
of others whom we perceive as physically, racially, or culturally different.
But these preferences, naturally selected for their past survival and reproductive consequences, are not necessarily advantageous in these respects
in the modern environment we inhabit.

The extended Bernardian lesson provides an explanation for how such
preferences, existing as reference levels within feedback-control systems,
influence our behavior, and how we are able to purposefully vary our
behavior to make our perceptions match these reference levels." [Book Link]

Vancouver JB, Putka DJ.
Analyzing Goal-Striving Processes and a Test of the Generalizability of Perceptual Control Theory.
Organ Behav Hum Decis Process 2000 Jul;82(2):334-362
"Theories that articulate dynamic processes are relatively rare, but methods for testing the theories are even rarer. This study illustrates two methods for examining goal-striving processes and a tool for collecting dynamic data. The first method tests a hypothesis regarding what variable the participants are attempting to maintain. The second method involves creating multilevel models used to describe the dynamic data generated by study participants, which can be used to test between- and within-subject manipulations or differences. The tool is a research simulation of a manager's role in scheduling subordinates in a hospital wing. Together these methods and the tool are used to test the generalizability of perceptual control theory in explaining striving for cognitive goals. The results confirm the viability of a control theory accounting of goal striving and highlight the potential of the methods and the research tool in future research." [Abstract]

Kent McClelland
The collective control of perceptions: constructing order from conflict
International Journal of Human-Computer Studies 2004 Jan;64(1): 65-99.
This article offers a new perspective on sociological theory, based on psychological insights from Perceptual Control Theory. After describing this cybernetic model of goal-directed behavior and reviewing its empirical support, I present results from computer simulations applying the model to the social interactions of elementary control agents. My key finding is that agents controlling their own perceptions of a single environmental variable can stabilize it even when their intentions conflict. The concluding section discusses implications of this model of collective control processes for the sources of order, conflict, continuity, and change in social life. [Abstract]

KENT McCLELLAND
PERCEPTUAL CONTROL AND SOCIAL POWER
Sociological Perspectives, Vol. 37, No. 4, pp. 461-496, 1994.
"This paper explores a new psychological perspective on human behavior, a cybernetic approach called "perceptual control theory" (PCT). After detailing the PCT model, I demonstrate one application of PCT to sociological theory by applying this perspective to questions of power and interpersonal control. I argue that social power should be distinguished from interpersonal use of force, coercion, incentives, or influence. Rather, power derives from an alignment of goals by humans acting as independent control systems. The paper closes with a discussion of connections between PCT and several strands of current sociological theory." [Full Text]

David M. Goldstein
Perceptual Control Theory Psychotherapy
[Article Link]

W. Thomas Bourbon
Perceptual Control Theory, Reinforcement Theory,
Countercontrol, and the Responsible Thinking Process ®
[Article Link]

W. Thomas Bourbon
Perceptual Control Theory, Reality Therapy, and the Responsible Thinking Process
[Article Link]

Bruce B. Abbott
A Synopsis of William T. Powers' Perceptual Control Theory
"HPCT [Hierarchical Perceptual Control Theory] proposes a second control mechanism lying outside of the perceptual control hierarchy. Called the reorganizing system, this mechanism functions to change the organization of the perceptual control hierarchy so as to remove damaging conflicts and improve control of perceptual signals at all levels. Reorganization can involve merely changing the parameters of control (e.g., the loop gain) within a given system so as to increase its efficiency or sensitivity or eliminate problems such as a tendency to oscillate. Alternatively, reorganization can involve establishing new connections between levels of the control hierarchy, destroying existing connections, or even creating new perceptual signals (by combining next-down perceptual signals in new ways) and new control systems to control them.

If a reorganizing system is to be effective, it must have a mechanism to determine when changes are needed, and some means of implementing the changes. Powers proposes (after Ashby, 1952) that what drives reorganization is persistent error in intrinsic variables. This presupposes some mechanism capable of sensing the states of these intrinsic variables, perhaps through chemical means if not via neural signals. According to Powers, these states are compared to genetically given reference values to compute the level of error. In Powers' proposal, reorganization occurs continually at a rate proportional to the level of persistent error. Thus reorganization will proceed more swiftly when error is large then when error is small, and may nearly cease entirely when persistent error is kept very low by the perceptual control hierarchy." [Article Link]

Fay D, Sonnentag S.
Rethinking the effects of stressors: a longitudinal study on personal initiative.
J Occup Health Psychol 2002 Jul;7(3):221-34
"This study examined the relationship between stressors at work and personal initiative (PI), one proactive concept of extra-role performance. Using a control theory framework to describe the stress process, the authors hypothesized that stressors should be positively related to PI. This departs from findings of negative relationships between stressors and other types of performance. Furthermore, curvilinear relationships were tested. The analyses, based on 4 measurement waves of a longitudinal field study with 172 to 193 participants, showed that stressors were positively related to subsequent changes in PI; there was no support for a curvilinear relationship." [Abstract]

Karel Pacák, and Miklós Palkovits
Stressor Specificity of Central Neuroendocrine Responses: Implications for Stress-Related Disorders
Endocr. Rev. 22: 502-548
"All of these data suggest the existence of stressor-specific central pathways that participate differentially in the regulation of sympathoneuronal and adrenomedullary outflow as well as activity of the HPA axis. Our conclusions further support our view and suggestions by others (483) that the neural representations of stress and other disease-related symptoms and signs cannot be described as a matter of altered function of one brain region or neurotransmitter. Rather, it reflects the activation of several circuits to orchestrate an optimal pattern of neuroendocrine and other responses. It is very likely that one of these circuits is the primary circuit, others are subordinate, and all combine to form the functional circuit to guarantee maximal plasticity of stress responses during acute as well as chronic stress conditions. Stressor-specific formation of new connections and disconnections of subordinate circuits with the primary one, anatomical and biochemical switches within the functional circuit, previous experience of an organism to an individual stressor, and genetically programmed neuronal and cellular functions precisely tune responses to stress and maximally protect from its deleterious effects. For example, in the response to an acute stressor, the failure of the primary circuit to function properly may have disastrous effects for an organism as is evident from neuroendocrine responses in patients with hypothalamic lesions; failure of subordinate circuits may contribute to milder symptoms and signs." [Full Text]

Buonomano DV, Merzenich MM.
Cortical plasticity: from synapses to maps.
Annu Rev Neurosci. 1998;21:149-86.
"It has been clear for almost two decades that cortical representations in adult animals are not fixed entities, but rather, are dynamic and are continuously modified by experience. The cortex can preferentially allocate area to represent the particular peripheral input sources that are proportionally most used. Alterations in cortical representations appear to underlie learning tasks dependent on the use of the behaviorally important peripheral inputs that they represent. The rules governing this cortical representational plasticity following manipulations of inputs, including learning, are increasingly well understood. In parallel with developments in the field of cortical map plasticity, studies of synaptic plasticity have characterized specific elementary forms of plasticity, including associative long-term potentiation and long-term depression of excitatory postsynaptic potentials. Investigators have made many important strides toward understanding the molecular underpinnings of these fundamental plasticity processes and toward defining the learning rules that govern their induction. The fields of cortical synaptic plasticity and cortical map plasticity have been implicitly linked by the hypothesis that synaptic plasticity underlies cortical map reorganization. Recent experimental and theoretical work has provided increasingly stronger support for this hypothesis. The goal of the current paper is to review the fields of both synaptic and cortical map plasticity with an emphasis on the work that attempts to unite both fields. A second objective is to highlight the gaps in our understanding of synaptic and cellular mechanisms underlying cortical representational plasticity."
...
"If there is a preferred flow of information vertically through the cortex, one
would expect to find different response characteristics in different cortical layers, since each stage of cortical processing is presumably contributing to the processing of information and thus transforming the neuronal response characteristics in some manner. Indeed, in general, receptive fields tend to be larger and responses tend to be more complex outside of L-IV. Experiments in rat and monkey somatosensory cortex indicate that the smallest receptive fields are found in L-IV, while supragranular layers exhibit larger receptive fields than those observed in L-IV, and infragranular layers exhibit the largest receptive fields (Simons 1978, Chapin 1986, Armstrong-James & Fox 1987) or sizes equivalent to those in the supragranular layers (Sur et al 1985). Laminar analysis in cat visual cortex indicates similar patterns. Gilbert (1977) reported that the smallest receptive fields were in L-IV, intermediate size fields were inL-III, and the largest receptive fields were in the infragranular layers. Other interlaminar differences include the observation that the degree of orientation tuning is also sharper in the supra- and infragranular layers (Chapman&Stryker 1993) and that the proportion of simple cells in the visual cortex is highest in L-IV, whereas complex cells are found mostly in supra- and infragranular layers (Hubel & Wiesel 1968, Gilbert 1977). Together these data support the notion that at each level of cortical processing, the neurons are sampling from a larger input space, receiving convergent information from the previous level, diverging out to the next level, and in the process, forming larger and more complexly integrated and combinatorial receptive fields.

In addition to the vertical flow of information, there is substantial horizontal interconnectivity, which integrates information from neighboring regions and from specific, more distant cortical zones (Lorente de N´o 1938). Excitatory horizontal projections arise mainly from L-II/III and L-V pyramidal cells and project preferentially to supra- and infragranular layers (e.g. Schwark & Jones 1989, White 1989, Abeles 1991, Tanifuji et al 1994). For any given layer, it is not clear what percentage of synapses originate from within the same cortical column, from more distant cortical regions, or from other cortical fields. However, even in L-IV, only 15–20% of the synapses are of thalamic origin (LeVay & Gilbert 1976, Benshalom & White 1986); most synapses seem to originate from intra- and interlaminar neurons. Horizontal connectivity may be of particular relevance in cortical map reorganization, since it appears that areas that develop novel receptive fields and other emergent response properties after peripheral input manipulations may rely in large part on connections from neighboring cortical sectors..." [Abstract] [PDF]

[Abstract] [PDF]

Biology Online: Regulation in Biological Systems

Hahnloser RH, Douglas RJ, Hepp K.
Attentional recruitment of inter-areal recurrent networks for selective gain control.
Neural Comput 2002 Jul;14(7):1669-89
"There is strong anatomical and physiological evidence that neurons with large receptive fields located in higher visual areas are recurrently connected to neurons with smaller receptive fields in lower areas. We have previously described a minimal neuronal network architecture in which top-down attentional signals to large receptive field neurons can bias and selectively read out the bottom-up sensory information to small receptive field neurons (Hahnloser, Douglas, Mahowald, & Hepp, 1999). Here we study an enhanced model, where the role of attention is to recruit specific inter-areal feedback loops (e.g., drive neurons above firing threshold). We first illustrate the operation of recruitment on a simple example of visual stimulus selection. In the subsequent analysis, we find that attentional recruitment operates by dynamical modulation of signal amplification and response multistability. In particular, we find that attentional stimulus selection necessitates increased recruitment when the stimulus to be selected is of small contrast and of small distance away from distractor stimuli. The selectability of a low-contrast stimulus is dependent on the gain of attentional effects; for example, low-contrast stimuli can be selected only when attention enhances neural responses. However, the dependence of attentional selection on stimulus-distractor distance is not contingent on whether attention enhances or suppresses responses. The computational implications of attentional recruitment are that cortical circuits can behave as winner-take-all mechanisms of variable strength and can achieve close to optimal signal discrimination in the presence of external noise." [Abstract] [PDF]

Burrone J, Murthy VN.
Synaptic gain control and homeostasis.
Curr Opin Neurobiol. 2003 Oct;13(5):560-7.
"Chronic changes in activity can induce neurons to alter the strength of all their synapses in unison. Although the specific changes that occur appear to vary depending on the experimental preparation, their net effect is to counter the experimentally induced modification of activity. Such adaptive, cell-wide changes in synaptic strength serve to stabilize neuronal activity and are collectively referred to as homeostatic synaptic plasticity. Recent studies have shed light on what triggers homeostatic synaptic plasticity, whether or not it is distinct from other forms of synaptic plasticity and whether or not it occurs in the intact brain." [Abstract] [PDF]

Davis GW, Bezprozvanny I.
Maintaining the stability of neural function: a homeostatic hypothesis.
Annu Rev Physiol. 2001;63:847-69.
"The precise regulation of neural excitability is essential for proper nerve cell, neural circuit, and nervous system function. During postembryonic development and throughout life, neurons are challenged with perturbations that can alter excitability, including changes in cell size, innervation, and synaptic input. Numerous experiments demonstrate that neurons are able to compensate for these types of perturbation and maintain appropriate levels of excitation. The mechanisms of compensation are diverse, including regulated changes to synaptic size, synaptic strength, and ion channel function in the plasma membrane. These data are evidence for homeostatic regulatory systems that control neural excitability. A model of neural homeostasis suggests that information about cell activity, cell size, and innervation is fed into a system of cellular monitors. Intracellular- and intercellular-signaling systems transduce this information into regulated changes in synaptic and ion channel function. This review discusses evidence for such a model of homeostatic regulation in the nervous system." [Abstract]

Abbott LF, Varela JA, Sen K, Nelson SB.
Synaptic depression and cortical gain control.
Science. 1997 Jan 10;275(5297):220-4.
"Cortical neurons receive synaptic inputs from thousands of afferents that fire action potentials at rates ranging from less than 1 hertz to more than 200 hertz. Both the number of afferents and their large dynamic range can mask changes in the spatial and temporal pattern of synaptic activity, limiting the ability of a cortical neuron to respond to its inputs. Modeling work based on experimental measurements indicates that short-term depression of intracortical synapses provides a dynamic gain-control mechanism that allows equal percentage rate changes on rapidly and slowly firing afferents to produce equal postsynaptic responses. Unlike inhibitory and adaptive mechanisms that reduce responsiveness to all inputs, synaptic depression is input-specific, leading to a dramatic increase in the sensitivity of a neuron to subtle changes in the firing patterns of its afferents." [Abstract]

Koch C, Segev I.
The role of single neurons in information processing.
Nat Neurosci. 2000 Nov;3 Suppl:1171-7.
"Neurons carry out the many operations that extract meaningful information from sensory receptor arrays at the organism's periphery and translate these into action, imagery and memory. Within today's dominant computational paradigm, these operations, involving synapses, membrane ionic channels and changes in membrane potential, are thought of as steps in an algorithm or as computations. The role of neurons in these computations has evolved conceptually from that of a simple integrator of synaptic inputs until a threshold is reached and an output pulse is initiated, to a much more sophisticated processor with mixed analog-digital logic and highly adaptive synaptic elements." [Abstract] [PDF]

Rainer G, Asaad WF, Miller EK.
Selective representation of relevant information by neurons in the primate prefrontal cortex.
Nature 1998 Jun 11;393(6685):577-9
"The severe limitation of the capacity of working memory, the ability to store temporarily and manipulate information, necessitates mechanisms that restrict access to it. Here we report tests to discover whether the activity of neurons in the prefrontal (PF) cortex, the putative neural correlate of working memory, might reflect these mechanisms and preferentially represent behaviourally relevant information. Monkeys performed a 'delayed-matching-to-sample' task with an array of three objects. Only one of the objects in the array was relevant for task performance and the monkeys needed to find that object (the target) and remember its location. For many PF neurons, activity to physically identical arrays varied with the target location; the location of the non-target objects had little or no influence on activity. Information about the target location was present in activity as early as 140ms after array onset. Also, information about which object was the target was reflected in the sustained activity of many PF neurons. These results suggest that the prefrontal cortex is involved in selecting and maintaining behaviourally relevant information." [Abstract]

Mao A, Freeman KA, Tallarida RJ.
Transient loss of dopamine autoreceptor control in the presence of highly potent dopamine agonists.
Life Sci 1996;59(21):PL317-24
"The concentrations of endogenous ligands generally remain in a bounded range around a basal level, a manifestation of control. The dopaminergic system is an excellent example of a control system in which a negative feedback signal is associated with receptor occupancy of a D2-like dopamine autoreceptor. A consequence of the control theory is that autoreceptor occupancy by an agonist results in dopamine levels below the basal, whereas similar stimulation by a dopamine competitive antagonist results in an increase of dopamine to levels above the basal. These consequences of control theory were tested and verified in the rat striatum by infusing graded doses of either the agonist, quinpirole, or the antagonist, sulpiride, into the rat striatum via a microdialysis probe and sampling dopamine and metabolite levels at various times after the start of infusion. Control was maintained even at the very highest doses of these compounds, i.e., striatal dopamine concentration rose in response to the antagonist and fell in response to the agonist. In contrast, administration of each of two high affinity dopamine agonists, 7-OH-DPAT and PPHT showed dose-dependent control only up to certain doses. Above these doses the dopamine concentration actually increased to levels well above basal, an indication of loss of control. These findings suggest that the control of this endogenous ligand does not extend to the very highest levels of autoreceptor occupancy." [Abstract]

Durstewitz, Daniel, Kelc, Marian, Gunturkun, Onur
A Neurocomputational Theory of the Dopaminergic Modulation of Working Memory Functions
J. Neurosci. 1999 19: 2807-2822
"The dopaminergic modulation of neural activity in the prefrontal cortex (PFC) is essential for working memory. Delay-activity in the PFC in working memory tasks persists even if interfering stimuli intervene between the presentation of the sample and the target stimulus. Here, the hypothesis is put forward that the functional role of dopamine in working memory processing is to stabilize active neural representations in the PFC network and thereby to protect goal-related delay-activity against interfering stimuli. To test this hypothesis, we examined the reported dopamine-induced changes in several biophysical properties of PFC neurons to determine whether they could fulfill this function. An attractor network model consisting of model neurons was devised in which the empirically observed effects of dopamine on synaptic and voltage-gated membrane conductances could be represented in a biophysically realistic manner. In the model, the dopamine-induced enhancement of the persistent Na+ and reduction of the slowly inactivating K+ current increased firing of the delay-active neurons, thereby increasing inhibitory feedback and thus reducing activity of the "background" neurons. Furthermore, the dopamine-induced reduction of EPSP sizes and a dendritic Ca2+ current diminished the impact of intervening stimuli on current network activity. In this manner, dopaminergic effects indeed acted to stabilize current delay-activity. Working memory deficits observed after supranormal D1-receptor stimulation could also be explained within this framework. Thus, the model offers a mechanistic explanation for the behavioral deficits observed after blockade or after supranormal stimulation of dopamine receptors in the PFC and, in addition, makes some specific empirical predictions." [Full Text]

Le Bars, Daniel, Gozariu, Manuela, Cadden, Samuel W.
Animal Models of Nociception
Pharmacol Rev 2001 53: 597-652
"Sensory systems have the role of informing the brain about the state of the external environment and the internal milieu of the organism. Pain is a perception, and as such, it is one of the outputs of a system in more highly evolved animals -- the nociceptive system -- which itself is a component of the overall set of controls responsible for homeostasis." [Full Text]

Melzack R.
From the gate to the neuromatrix.
Pain 1999 Aug;Suppl 6:S121-6
"The gate control theory's most important contribution to understanding pain was its emphasis on central neural mechanisms. The theory forced the medical and biological sciences to accept the brain as an active system that filters, selects and modulates inputs. The dorsal horns, too, were not merely passive transmission stations but sites at which dynamic activities (inhibition, excitation and modulation) occurred. The great challenge ahead of us is to understand brain function. I have therefore proposed that the brain possesses a neural network--the body-self neuromatrix--which integrates multiple inputs to produce the output pattern that evokes pain. The body-self neuromatrix comprises a widely distributed neural network that includes parallel somatosensory, limbic and thalamocortical components that subserve the sensory-discriminative. affective-motivational and evaluative-cognitive dimensions of pain experience. The synaptic architecture of the neuromatrix is determined by genetic and sensory influences. The 'neurosignature' output of the neuromatrix--patterns of nerve impulses of varying temporal and spatial dimensions--is produced by neural programs genetically build into the neuromatrix and determines the particular qualities and other properties of the pain experience and behavior. Multiple inputs that act on the neuromatrix programs and contribute to the output neurosignature include. (1) sensory inputs (cutaneous, visceral and other somatic receptors); (2) visual and other sensory inputs that influence the cognitive interpretation of the situation; (3) phasic and tonic cognitive and emotional inputs from other areas of the brain; (4) intrinsic neural inhibitory modulation inherent in all brain function; (5) the activity of the body's stress-regulation systems, including cytokines as well as the endocrine, autonomic, immune and opioid systems. We have traveled a long way from the psychophysical concept that seeks a simple one-to-one relationship between injury and pain. We now have a theoretical framework in which a genetically determined template for the body-self is modulated by the powerful stress system and the cognitive functions of the brain, in addition to the traditional sensory inputs." [Abstract]

Reichling DB, Levine JD.
The primary afferent nociceptor as pattern generator.
Pain 1999 Aug;Suppl 6:S103-9
"One of the most important advances in our understanding of the pain experience was the introduction of the 'gate control' theory which stimulated analysis of activity pattern in nociceptive pathways and its modulation. Advances in cellular and molecular biology have recently begun to provide detailed information on the mechanisms of stimulus transduction within primary afferent nociceptors as well as mechanisms that modulate the transduction process. From these new insights into the sensory physiology of the nociceptive nerve ending emerges a concept of the primary afferent as the first site of pattern generation in the nociceptive pathway, in which dynamic tuning of gain in the mosaic of inputs to individual primary afferents occurs. The electrical properties of the nociceptor membrane that converts the generator potential to a pattern of action potentials is also actively adjusted." [Abstract]

Kobayashi S.
Warm- and cold-sensitive neurons inactive at normal core temperature in rat hypothalamic slices.
Brain Res 1986 Jan 1;362(1):132-9
"Electrical activities of thermosensitive neurons were recorded extracellularly in slices of rat preoptic area and anterior hypothalamus. Of 63 spontaneously firing neurons found at high searching temperature (37-40 degrees C), 33% were warm-sensitive, 8% were cold-sensitive and the remaining 59% were thermally insensitive. In particular, 6 warm-sensitive neurons were active only above 38 degrees C of rat normal core temperature. In contrast, of 38 spontaneously firing neurons found at low searching temperature (32-36 degrees C), 8% were warm-sensitive, 29% were cold-sensitive and the remaining 63% were thermally insensitive. Furthermore, all these cold-sensitive neurons were active only below 38 degrees C. Therefore, the warm- and cold-sensitive neurons active at 38 degrees C would be functioning for narrow band control and the remaining warm- and cold-sensitive neurons inactive at 38 degrees C would be recruited for wide band control when core temperature was changed critically from 38 degrees C. Their firing rate activities often showed obvious threshold responses, large hysteresis of the threshold responses and remarkable transient responses to slice temperature changes. From aspects of automatic control theory, these warm- and cold-sensitive neurons themselves may be thermostats to regulate the brain temperature rather than thermosensors to monitor it." [Abstract]

Sun JR, Ma YC, Xu ZH, Zhao WJ, Cai YP.
[Effect of norepinephrine on the thermosensitive neurons in preoptic area of hypothalamus tissue slices in cold acclimatized rats]
Sheng Li Xue Bao 1997 Dec;49(6):666-70
"In this work, single unit firing activities were recorded in the preoptic anterior hypothalamus (POAH) brain slices of cold acclimatized and room-temperature housed rats (CR and RR) and the effects of NE on the neuronal discharges were observed. The neurons of POAH in CR became much more sensitive to NE than that in RR (the threshold concentration of NE of CR became significantly lowered). In comparison with RR, the percentage of warm sensitive neurons that could be excited by NE was decreased and some of them even showed inhibitory responses. On the other hand, the percentage of cold sensitive neurons that could be inhibited by NE was decreased and some of them even showed excitatory responses. The percentage of thermo-insensitive neurons that could be either excited or inhibited by NE were increased." [Abstract]

Meyer-Lindenberg A, Ziemann U, Hajak G, Cohen L, Berman KF.
Transitions between dynamical states of differing stability in the human brain.
Proc Natl Acad Sci U S A 2002 Aug 20;99(17):10948-53
"What mechanisms underlie the flexible formation, adaptation, synchronization, and dissolution of large-scale neural assemblies from the 10(10) densely interconnected, continuously active neurons of the human brain? Nonlinear dynamics provides a unifying perspective on self-organization. It shows that the emergence of patterns in open, nonequilibrium systems is governed by their stability in response to small disturbances and predicts macroscopic transitions between patterns of differing stability. Here, we directly demonstrate that such transitions can be elicited in the human brain by interference at the neural level. As a probe, we used a classic motor coordination paradigm exhibiting well described movement states of differing stability. Functional neuroimaging identified premotor (PMA) and supplementary motor (SMA) cortices as having neural activity linked to the degree of behavioral instability. These regions then were transiently disturbed with graded transcranial magnetic stimulation, which caused sustained and macroscopic behavioral transitions from the less stable out-of-phase to the stable in-phase movement, whereas the stable pattern could not be affected. Moreover, the strength of the disturbance needed (a measure of neural stability) was linked to the degree of behavioral stability, demonstrating the applicability of nonlinear system theory as a powerful predictor of the dynamical repertoire of the human brain." [Abstract]

Abe H.
Nutrition and control theory.
J Nutr Sci Vitaminol (Tokyo) 1991 Dec;37 Suppl:S5-12
"Organ homeostasis in humans is maintained by the "auto-regulatory system." Although this biological regulatory system is regarded as complicated and difficult to analyze, with the aid of control theory it has become possible for us to construct a mathematical model. To date we have created models for water-electrolyte balance and glucose metabolism. The validity of these models has been evaluated by simulation study. As a clinical application of the model, we have successfully developed an artificial pancreas system for the treatment of diabetic patients. Through this system, we have made many contributions to the study of clinical nutrition and we feel that this has initiated a new era in this field. In order to make further progress in this field, it will be necessary to take a new dynamic and systemic approach." [Abstract]

Peters A, Schweiger U, Fruhwald-Schultes B, Born J, Fehm HL.
The neuroendocrine control of glucose allocation.
Exp Clin Endocrinol Diabetes 2002 Jul;110(5):199-211
"Summary. Here we propose that glucose metabolism can be understood on the basis of three concept-derived axioms: (I) A hierarchy exists among the glucose-utilizing organs with the brain served first, followed by muscle and fat. (II) Tissue-specific glucose transporters allocate glucose among organs in order to maintain brain glucose concentrations. (III) Exogenous carbohydrate supply compensates for glucose alterations that can temporarily occur in muscle and fat. Derived from the control theory, the simplest solution of allocating supply to 2 organs, e.g. brain and muscle, is a "fishbone"-structured model. We reviewed the literature, searching for neuroendocrine and metabolic mechanisms that can fulfill control functions in such a model: The tissue-specific glucose transporters are differentially regulated. GLUT 1, carrying glucose across the blood-brain-barrier, is independent of insulin. Instead, this trans-endothelial glucose transporter is rather dependent on potent regulators of blood vessel function like vascular endothelial growth factor - a pituitary counterregulatory hormone. GLUT 4, carrying glucose across the membranes of muscle and fat cells, depends on insulin. Thereby, insulin allocates glucose to muscle and fat. The hypothalamus-pituitary-adrenal (HPA) axis, the sympathetic nervous system (SNS), and vascular endothelial growth factor allocate glucose to the brain. Multiple "sensors" (some of which have only recently been identified as ATP sensitive potassium channels) measure glucose or glucose equivalents at various sites of the body: the ventromedial hypothalamus, the lateral hypothalamus, portal vein, pancreatic beta cell, renal tubule, muscle and adipose tissue. Feedback pathways both from the brain and from muscle and fat are involved in regulating glucose allocation and exogenous glucose supply. The main feedback signal from the brain is found to be glucose, that from muscle and fat appears to be leptin. In fact, the literature search revealed two or more biological mechanisms for the function of each component in the model, finding glucose regulation highly redundant. This review focuses on "brain glucose" control. The concept of glucose allocation presented here challenges the common opinion of "blood glucose" being the main parameter controlled. According to the latter opinion, hyperglycemia in the metabolic syndrome is due to a putative defect located within the closed loop including the beta cell, muscle and fat cells. That traditional view leaves some peculiarities of e.g. the metabolic syndrome unexplained. The concept of glucose allocation, however, would predict that weight gain - with abundance of glucose in muscle and fat - increases feedback to the brain (via hyperleptinemia) which in turn results in HPA-axis and SNS overdrive, impaired insulin secretion, and insulin resistance. HPA-axis overdrive would account for metabolic abnormalities such as central adiposity, hyperglycemia, dyslipidemia, and hypertension, that are well known clinical aspects the metabolic syndrome. This novel viewpoint of "brain glucose" control may shed new light on the pathogenesis of the metabolic syndrome and type 2 diabetes." [Abstract]

Heap RB, Galil AK, Harrison FA, Jenkin G, Perry JS.
Progesterone and oestrogen in pregnancy and parturition: comparative aspects and hierarchical control.
Ciba Found Symp 1977;(47):127-57
"The different ways in which the progesterone requirements of pregnancy are met in various species are reviewed here. Progesterone production expressed in terms of metabolic body weight lies within about one order of magnitude in several species (but not in the rat), whether the hormone is predominantly ovarian or placental in origin. Parturition is usually preceded by a decrease in the plasma concentration of progesterone and the evidence which suggests that a decrease in secretion involves enzyme induction is summarized. In the sheep a sequence of well-marked hormonal changes can be discerned--an increase in fetal cortisol secretion followed by a fall in placental progesterone and a rise in oestrogen and prostaglandin F2alpha secretion. This sequence has been interpreted in terms of hierarchical control theory which envisages a series of levels placed in a descending order of importance and in which there is a downward transmission of a signal from a higher level that modifies activity at a lower level. A dominant level in the hierarchy in the sheep and pig seems to be the fetal hypothalamus and pituitary, but in the rabbit the maternal hypothalamus, pituitary and ovary play a more dominant role." [Abstract]

Gerald M. Edelman, and Joseph A. Gally
Degeneracy and complexity in biological systems
PNAS 98: 13763-13768; published online before print as 10.1073/pnas.231499798
"Degeneracy, the ability of elements that are structurally different to perform the same function or yield the same output, is a well known characteristic of the genetic code and immune systems. Here, we point out that degeneracy is a ubiquitous biological property and argue that it is a feature of complexity at genetic, cellular, system, and population levels. Furthermore, it is both necessary for, and an inevitable outcome of, natural selection." [Full Text]

Giulio Tononi, Olaf Sporns, and Gerald M. Edelman
Measures of degeneracy and redundancy in biological networks
PNAS 96: 3257-3262, 1999.
"Degeneracy, the ability of elements that are structurally different to perform the same function, is a prominent property of many biological systems ranging from genes to neural networks to evolution itself. Because structurally different elements may produce different outputs in different contexts, degeneracy should be distinguished from redundancy, which occurs when the same function is performed by identical elements. However, because of ambiguities in the distinction between structure and function and because of the lack of a theoretical treatment, these two notions often are conflated. By using information theoretical concepts, we develop here functional measures of the degeneracy and redundancy of a system with respect to a set of outputs. These measures help to distinguish the concept of degeneracy from that of redundancy and make it operationally useful. Through computer simulations of neural systems differing in connectivity, we show that degeneracy is low both for systems in which each element affects the output independently and for redundant systems in which many elements can affect the output in a similar way but do not have independent effects. By contrast, degeneracy is high for systems in which many different elements can affect the output in a similar way and at the same time can have independent effects. We demonstrate that networks that have been selected for degeneracy have high values of complexity, a measure of the average mutual information between the subsets of a system. These measures promise to be useful in characterizing and understanding the functional robustness and adaptability of biological networks." [Full Text]

Emmons RA.
Abstract versus concrete goals: personal striving level, physical illness, and psychological well-being.
J Pers Soc Psychol 1992 Feb;62(2):292-300
"This study examined the relation between personal striving level and psychological and physical well-being. Level refers to the degree of generality versus specificity of one's goal strivings. In 3 studies, 188 Ss generated lists of their personal strivings, which were then rated on specificity level. High-level striving was associated with more psychological distress, particularly depression. Low-level striving was related to higher levels of physical illness. Correlations between striving level and self-reported symptoms were generally not as strong as those between level and the more objective illness indicators. High-level strivings were seen as more difficult and requiring more effort than low-level strivings. Results are interpreted in terms of control theory, goal-setting theory, and the repressive personality style." [Abstract]

Vancouver JB, Thompson CM, Tischner EC, Putka DJ.
Two studies examining the negative effect of self-efficacy on performance.
J Appl Psychol 2002 Jun;87(3):506-16
"Although hundreds of studies have found a positive relationship between self-efficacy and performance, several studies have found a negative relationship when the analysis is done across time (repeated measures) rather than across individuals. W. T. Powers (1991) predicted this negative relationship based on perceptual control theory. Here, 2 studies are presented to (a) confirm the causal role of self-efficacy and (b) substantiate the explanation. In Study 1, self-efficacy was manipulated for 43 of 87 undergraduates on an analytic game. The manipulation was negatively related to performance on the next trial. In Study 2, 104 undergraduates played the analytic game and reported self-efficacy between each game and confidence in the degree to which they had assessed previous feedback. As expected, self-efficacy led to overconfidence and hence increased the likelihood of committing logic errors during the game." [Abstract]

Kim Y.
The role of cognitive control in mediating the effect of stressful circumstances among Korean immigrants.
Health Soc Work 2002 Feb;27(1):36-46
"The study reported in this article investigated relationships among stressful circumstances, cognitive control (the individual's perception of control over life), and distress among Korean immigrants in the United States. Specifically, it was hypothesized that cognitive control mediated the effect of exposure to stressful circumstances on distress. A total of 159 Korean immigrants participated in the study. The result of the study provided strong support for the role of cognitive control in mediating the relationship between stressful circumstances and distress. The detrimental effect of exposure to stressful circumstances on distress was weakened by cognitive control." [Abstract]

Coping with unplanned childhood hospitalization: the mediating functions of parental beliefs.
J Pediatr Psychol 1995 Jun;20(3):299-312
"Examined the processes by which two types of informational interventions (child behavioral information and parental role information) exerted effects on the coping outcomes of 108 mothers whose young children experienced unplanned hospitalization. Driven by a strong theoretical framework comprising self-regulation theory and control theory, this study's findings revealed that the effects of the experimental interventions were mediated by parental beliefs about their children's likely behavioral changes and their parental role during hospitalization. Thus, progress was made in beginning to understand how informational interventions actually enhance parent coping with childhood hospitalization." [Abstract]

Kobak RR, Cole HE, Ferenz-Gillies R, Fleming WS, Gamble W.
Attachment and emotion regulation during mother-teen problem solving: a control theory analysis.
Child Dev 1993 Feb;64(1):231-45
"We present a control theory analysis of adolescents' attachment strategies in the Adult Attachment Interview (AAI). In Study 1, Q-sort prototypes for secure/anxious and deactivating/hyperactivating strategies were used to differentiate between Main and Goldwyn's AAI classifications. In Study 2, we examined how AAI strategies were associated with emotion regulation during mother-teen problem solving. 4 aspects of mother-teen problem solving (dysfunctional anger, support/validation, avoidance of problem solving, and maternal dominance) were used to predict teens' AAI strategies. Teens with secure strategies engaged in problem-solving discussions characterized by less dysfunctional anger and less avoidance of problem solving. In addition, attachment security showed a curvilinear relation with maternal dominance, indicating that secure teens maintained balanced assertiveness with their mothers. Teens with deactivating strategies engaged in problem-solving interactions characterized by higher levels of maternal dominance and dysfunctional anger. The contribution of attachment strategies to teens' autonomy and to transformations in mother-teen relationships is discussed." [Abstract]

Posner MI, Rothbart MK.
Attention, self-regulation and consciousness.
Philos Trans R Soc Lond B Biol Sci. 1998 Nov 29;353(1377):1915-27.
"Consciousness has many aspects. These include awareness of the world, feelings of control over one's behaviour and mental state (volition), and the notion of continuing self. Focal (executive) attention is used to control details of our awareness and is thus closely related to volition. Experiments suggest an integrated network of neural areas involved in executive attention. This network is associated with our voluntary ability to select among competing items, to correct error and to regulate our emotions. Recent neuroimaging studies suggest that these various functions involve separate areas of the anterior cingulate. We have adopted a strategy of using marker tasks, shown to activate the brain area by imaging studies, as a means of tracing the development of attentional networks. Executive attention appears to develop first to regulate distress during the first year of life. During later childhood the ability to regulate conflict among competing stimuli builds upon the earlier cingulate anatomy to provide a means of cognitive control. During childhood the activation of cingulate structures relates both to the child's success on laboratory tasks involving conflict and to parental reports of self-regulation and emotional control. These studies indicate a start in understanding the anatomy, circuitry and development of executive attention networks that serve to regulate both cognition and emotion." [Abstract]

Aarts H, Dijksterhuis A, De Vries P.
On the psychology of drinking: being thirsty and perceptually ready.
Br J Psychol 2001 Nov;92(Pt 4):631-42
"The present research is concerned with cognitive effects of habitually regulated primary motives. Specifically, two experiments tested the idea that feelings of thirst enhance the cognitive accessibility of, or readiness to perceive, action-relevant stimuli. In a task allegedly designed to assess mouth-detection skills, some participants were made to feel thirsty, whereas others were not. Results showed that participants who were made thirsty responded faster to drinking-related items in a lexical decision task, and performed better on an incidental recall task of drinking-related items, relative to no-thirst control participants. These results suggest that basic needs and motives, such as thirst, causes a heightened perceptual readiness to environmental cues that are instrumental in satisfying these needs." [Abstract]

Toppino TC.
Reversible-figure perception: mechanisms of intentional control.
Percept Psychophys. 2003 Nov;65(8):1285-95.
"Observers can exert a degree of intentional control over the perception of reversible figures. Also, the portion of the stimulus that is selected for primary or enhanced processing (focal-feature processing) influences how observers perceive a reversible figure. Two experiments investigated whether voluntary control over perception of a Necker cube could be explained in terms of intentionally selecting appropriate focal features within the stimulus for primary processing. In Experiment 1, varying observers' intentions and the focus of primary processing produced additive effects on the percentage of time that one alternative was perceived. In Experiment 2, the effect of varying the focus of primary processing was eliminated by the use of a small cube, but the effect of intention was unaltered. The results indicate that intentional control over perception can be exerted independently of focal-feature processing, perhaps by top-down activation or priming of perceptual representations. The results also reveal the limits of intentional control." [Abstract]

Gilbert CD, Sigman M, Crist RE.
The neural basis of perceptual learning.
Neuron 2001 Sep 13;31(5):681-97
"Perceptual learning is a lifelong process. We begin by encoding information about the basic structure of the natural world and continue to assimilate information about specific patterns with which we become familiar. The specificity of the learning suggests that all areas of the cerebral cortex are plastic and can represent various aspects of learned information. The neural substrate of perceptual learning relates to the nature of the neural code itself, including changes in cortical maps, in the temporal characteristics of neuronal responses, and in modulation of contextual influences. Top-down control of these representations suggests that learning involves an interaction between multiple cortical areas." [Abstract]

Smith, Edward E., Jonides, John
Storage and Executive Processes in the Frontal Lobes
Science 1999 283: 1657-1661
"Most researchers concur that executive processes are mediated by PFC and are involved in the regulation of processes operating on the contents of working memory. Although there is lack of consensus about a taxonomy of executive processes, there is some agreement that they include (i) focusing attention on relevant information and processes and inhibiting irrelevant ones ("attention and inhibition"); (ii) scheduling processes in complex tasks, which requires the switching of focused attention between tasks ("task management"); (iii) planning a sequence of subtasks to accomplish some goal ("planning"); (iv) updating and checking the contents of working memory to determine the next step in a sequential task ("monitoring"); and (v) coding representations in working memory for time and place of appearance ("coding")." [Full Text]

Wagner AD, Maril A, Bjork RA, Schacter DL.
Prefrontal contributions to executive control: fMRI evidence for functional distinctions within lateral Prefrontal cortex.
Neuroimage. 2001 Dec;14(6):1337-47.
"The prefrontal cortex (PFC) plays a fundamental role in internally guided behavior. Although it is generally accepted that PFC subserves working memory and executive control operations, it remains unclear whether the subregions within lateral PFC support distinct executive control processes. An event-related fMRI study was implemented to test the hypothesis that ventrolateral and dorsolateral PFC are functionally distinct, as well as to assess whether functional specialization exists within ventrolateral PFC. Participants performed two executive control tasks that differed in the types of control processes required. During rote rehearsal, participants covertly rehearsed three words in the order presented, thus requiring phonological access and maintenance. During elaborative rehearsal, participants made semantic comparisons between three words held in working memory, reordering them from least to most desirable. Thus, in addition to maintenance, elaborative rehearsal required goal-relevant coding of items in working memory ("monitoring") and selection from among the items to implement their reordering. Results revealed that left posterior ventrolateral PFC was active during performance of both tasks, whereas right dorsolateral PFC was differentially engaged during elaborative rehearsal. The temporal characteristics of the hemodynamic responses further suggested that dorsolateral activation lagged ventrolateral activation. Finally, differential activation patterns were observed within left ventrolateral PFC, distinguishing between posterior and anterior regions. These data suggest that anatomically separable subregions within lateral PFC may be functionally distinct and are consistent with models that posit a hierarchical relationship between dorsolateral and ventrolateral regions such that the former monitors and selects goal-relevant representations being maintained by the latter. [Abstract] [PDF]

Miller, Earl K., Cohen, Jonathan D.
AN INTEGRATIVE THEORY OF PREFRONTAL CORTEX FUNCTION
Annu. Rev. Neurosci. 2001 24: 167-202
"The prefrontal cortex has long been suspected to play an important role in cognitive control, in the ability to orchestrate thought and action in accordance with internal goals. Its neural basis, however, has remained a mystery. Here, we propose that cognitive control stems from the active maintenance of patterns of activity in the prefrontal cortex that represent goals and the means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task. We review neurophysiological, neurobiological, neuroimaging, and computational studies that support this theory and discuss its implications as well as further issues to be addressed." [Abstract] [Full Text PDF]

Hunter MD, Farrow TF, Papadakis NG, Wilkinson ID, Woodruff PW, Spence SA.
Approaching an ecologically valid functional anatomy of spontaneous "willed" action.
Neuroimage. 2003 Oct;20(2):1264-9.
"We used functional magnetic resonance imaging of healthy subjects to investigate the neural basis for spontaneous "willed" action. We hypothesised that such action involves prefrontal cortex (PFC) and supplementary motor area (SMA), in addition to primary motor cortex. Furthermore, we predicted that PFC and SMA would demonstrate similar temporal response dynamics, distinct from primary motor cortex. Specifically, we predicted earlier activation in PFC and SMA, manifest as shorter response latencies compared with primary motor cortex. Six right-handed males participated in an event-related design and were required to generate spontaneous motor acts inside the scanner. By deciding "which" of two buttons to press, and "when" to press them, subjects generated sequences of action that were of high information content ("novelty" or "randomness"). Utilising a short repetition time (1 s), we acquired functional images that covered most of the frontal and parietal cortices. The onset of action was associated with significant activation in bilateral PFC, left primary motor cortex, and, close to the midline, SMA. Following action, mean time to half-maximum blood oxygenation level-dependent response was significantly earlier in left PFC and SMA than primary motor cortex. Our findings suggest that neural correlates of spontaneous willed action are distributed in executive and motor centres, and that temporal response dynamics differentiate "higher" regions from subordinate motor areas." [Abstract]

St Clair Gibson A, Baden D, Lambert M, Lambert E, Harley Y, Hampson D, Russell V, Noakes T.
The Conscious Perception of the Sensation of Fatigue.
Sports Med 2003;33(3):167-176
"In this review, fatigue is described as a conscious sensation rather than a physiological occurrence. We suggest that the sensation of fatigue is the conscious awareness of changes in subconscious homeostatic control systems, and is derived from a temporal difference between subconscious representations of these homeostatic control systems in neural networks that are induced by changes in the level of activity. These mismatches are perceived by consciousness-producing structures in the brain as the sensation of fatigue. In this model, fatigue is a complex emotion affected by factors such as motivation and drive, other emotions such as anger and fear, and memory of prior activity. It is not clear whether the origin of the conscious sensation of fatigue is associated with particular localised brain structures, or is the result of electrophysiological synchronisation of entire brain activity." [Abstract]

Moores E, Laiti L, Chelazzi L.
Associative knowledge controls deployment of visual selective attention.
Nat Neurosci 2003 Feb;6(2):182-189
"According to some models of visual selective attention, objects in a scene activate corresponding neural representations, which compete for perceptual awareness and motor behavior. During a visual search for a target object, top-down control exerted by working memory representations of the target's defining properties resolves competition in favor of the target. These models, however, ignore the existence of associative links among object representations. Here we show that such associations can strongly influence deployment of attention in humans. In the context of visual search, objects associated with the target were both recalled more often and recognized more accurately than unrelated distractors. Notably, both target and associated objects competitively weakened recognition of unrelated distractors and slowed responses to a luminance probe. Moreover, in a speeded search protocol, associated objects rendered search both slower and less accurate. Finally, the first saccades after onset of the stimulus array were more often directed toward associated than control items." [Abstract]

Bar, Moshe
A Cortical Mechanism for Triggering Top-Down Facilitation in Visual Object Recognition
J. Cogn. Neurosci. 2003 15: 600-609
"The majority of the research related to visual recognition has so far focused on bottom-up analysis, where the input is processed in a cascade of cortical regions that analyze increasingly complex information. Gradually more studies emphasize the role of top-down facilitation in cortical analysis, but it remains something of a mystery how such processing would be initiated. After all, top-down facilitation implies that high-level information is activated earlier than some relevant lower-level information. Building on previous studies, I propose a specific mechanism for the activation of top-down facilitation during visual object recognition. The gist of this hypothesis is that a partially analyzed version of the input image (i.e., a blurred image) is projected rapidly from early visual areas directly to the prefrontal cortex (PFC). This coarse representation activates in the PFC expectations about the most likely interpretations of the input image, which are then back-projected as an "initial guess" to the temporal cortex to be integrated with the bottom-up analysis. The top-down process facilitates recognition by substantially limiting the number of object representations that need to be considered. Furthermore, such a rapid mechanism may provide critical information when a quick response is necessary." [Abstract] [PDF]

Sussman E, Winkler I, Schroger E.
Top-down control over involuntary attention switching in the auditory modality.
Psychon Bull Rev. 2003 Sep;10(3):630-7.
"We tested the effects of predictability on involuntary attention switching to task-irrelevant sound changes (distraction). Behavioral and neurophysiological evidence are provided, showing that the predictability of task-irrelevant sound changes eliminates effects of distraction even though the automatic auditory change detection system remains responsive. Two indices of distraction, slower task performance and cortical brain responses associated with attention switching, were seen only in the unpredictable condition, in which the irrelevant acoustic changes were unexpected. Attention was not involuntarily drawn away from the primary task when the subjects had foreknowledge of when the irrelevant changes would occur. These results demonstrate attentional control over orienting to sound changes and suggest that involuntary attention switching occurs mainly when an irrelevant stimulus change is unexpected. The present data allowed observation of the temporal dynamics of attention switching in the human brain." [Abstract]

Liu T, Slotnick SD, Serences JT, Yantis S.
Cortical mechanisms of feature-based attentional control.
Cereb Cortex. 2003 Dec; 13(12): 1334-43.
"A network of fronto-parietal cortical areas is known to be involved in the control of visual attention, but the representational scope and specific function of these areas remains unclear. Recent neuroimaging evidence has revealed the existence of both transient (attention-shift) and sustained (attention-maintenance) mechanisms of space-based and object-based attentional control. Here we investigate the neural mechanisms of feature-based attentional control in human cortex using rapid event-related functional magnetic resonance imaging (fMRI). Subjects viewed an aperture containing moving dots in which dot color and direction of motion changed once per second. At any given moment, observers attended to either motion or color. Two of six motion directions and two of six colors embedded in the stimulus stream cued subjects either to shift attention from the currently attended to the unattended feature or to maintain attention on the currently attended feature. Attentional modulation of the blood oxygenation level dependent (BOLD) fMRI signal was observed in early visual areas that are selective for motion and color. More importantly, both transient and sustained BOLD activity patterns were observed in different fronto-parietal cortical areas during shifts of attention. We suggest these differing temporal profiles reflect complementary roles in the control of attention to perceptual features." [Abstract]

Ullsperger M, von Cramon DY, Muller NG.
Interactions of focal cortical lesions with error processing: evidence from event-related brain potentials.
Neuropsychology. 2002 Oct;16(4):548-61.
"Electrophysiological and hemodynamic studies have suggested that structures in the vicinity of the anterior cingulate cortex are involved in performance monitoring, particularly in detection of errors. Bidirectional interactions between the frontomedian system involved in performance monitoring and the lateral prefrontal cortex as well as the orbitofrontal cortex have been proposed, but few studies have directly addressed this issue. The authors used a speeded flankers task to investigate error-related event-related potentials in 3 patient groups with different focal cortical lesions. Whereas bilateral frontopolar lesions involving the orbitofrontal cortex as well as temporal lesions did not alter the error-related negativity (ERN), lesions of the lateral frontal cortex resulted in an abolition of the ERN and in a reduction of the error positivity." [Abstract]

Bishop S, Duncan J, Brett M, Lawrence AD.
Prefrontal cortical function and anxiety: controlling attention to threat-related stimuli.
Nat Neurosci. 2004 Feb;7(2):184-8. Epub 2004 Jan 04.
"Threat-related stimuli are strong competitors for attention, particularly in anxious individuals. We used functional magnetic resonance imaging (fMRI) with healthy human volunteers to study how the processing of threat-related distractors is controlled and whether this alters as anxiety levels increase. Our work builds upon prior analyses of the cognitive control functions of lateral prefrontal cortex (lateral PFC) and anterior cingulate cortex (ACC). We found that rostral ACC was strongly activated by infrequent threat-related distractors, consistent with a role for this area in responding to unexpected processing conflict caused by salient emotional stimuli. Participants with higher anxiety levels showed both less rostral ACC activity overall and reduced recruitment of lateral PFC as expectancy of threat-related distractors was established. This supports the proposal that anxiety is associated with reduced top-down control over threat-related distractors. Our results suggest distinct roles for rostral ACC and lateral PFC in governing the processing of task-irrelevant, threat-related stimuli, and indicate reduced recruitment of this circuitry in anxiety." [Abstract]

Hasselmo ME.
Neuromodulation and cortical function: modeling the physiological basis of behavior.
Behav Brain Res 1995 Feb;67(1):1-27
"Neuromodulators including acetylcholine, norepinephrine, serotonin, dopamine and a range of peptides alter the processing characteristics of cortical networks through effects on excitatory and inhibitory synaptic transmission, on the adaptation of cortical pyramidal cells, on membrane potential, on the rate of synaptic modification, and on other cortical parameters. Computational models of self-organization and associative memory function in cortical structures such as the hippocampus, piriform cortex and neocortex provide a theoretical framework in which the role of these neuromodulatory effects can be analyzed. Neuromodulators such as acetylcholine and norepinephrine appear to enhance the influence of synapses from afferent fibers arising outside the cortex relative to the synapses of intrinsic and association fibers arising from other cortical pyramidal cells. This provides a continuum between a predominant influence of external stimulation to a predominant influence of internal recall (extrinsic vs. intrinsic). Modulatory influence along this continuum may underlie effects described in terms of learning and memory, signal to noise ratio, and attention." [Abstract]

Polk TA, Simen P, Lewis RL, Freedman E.
A computational approach to control in complex cognition.
Brain Res Cogn Brain Res 2002 Dec;15(1):71-83
"Cognitive deficits associated with dorsolateral prefrontal cortex (DLPFC) damage are often most apparent in higher cognitive tasks that involve problem solving and managing multiple goals. However, computational models of prefrontal deficits on such tasks are difficult to construct. Problem solving is most naturally modeled with symbolic systems (e.g. production systems), but the effects of lesions are most naturally modeled with subsymbolic systems (neural networks). We show that when we adopt a simple and plausible model of neural computation, there is a natural and explicit mapping from symbolic, goal-driven cognition onto neural computation. We exploit this mapping to construct a neural network model that is capable of solving complex problems in the Tower of London task. The model leads to a specific hypothesis about the role of DLPFC in such tasks, namely, that DLPFC represents internally generated subgoals that modulate competition among posterior representations. When intact, the model accurately simulates the behavior of college students even on the most difficult problems. Furthermore, when the subgoal component is lesioned, it accurately simulates the behavior of prefrontal patients, including the fact that their deficits are most apparent on the most difficult tasks and that they have special difficulty with tasks that require inhibiting a prepotent response." [Abstract]

Cameron S. Carter, Angus M. Macdonald, Matthew Botvinick, Laura L. Ross, V. Andrew Stenger, Douglas Noll, and Jonathan D. Cohen
Parsing executive processes: Strategic vs. evaluative functions of the anterior cingulate cortex
PNAS 97: 1944-1948, 2000.
"Under conditions in which their performance indicated that subjects were engaging strategic processes to reduce the effects of response conflict, no increased activity was observed in the ACC. This is inconsistent with the theory that the ACC implements strategic processes to minimize the degree of conflict elicited by the task. In contrast, when subjects' performance indicated that strategic processes were less engaged and conflict high, a transient increase in activity was observed in this region of the brain. This result suggests that the ACC performs an evaluative function, reflecting the degree of response conflict elicited by the task. Because the ERN literature suggests that ACC activity is associated with subsequent "corrective" actions, it is likely that other components of the neural network implementing executive functions are influenced by ACC activity to implement strategic processes. This is consistent with the hypothesized central role for this brain region in the executive control of cognition (27-29). In the present view, the ACC would serve this function by providing an on-line conflict signal, indicating the need to engage brain regions such as dorsolateral prefrontal cortex and IPL to implement strategic processes (2). As such, the ACC would serve as one component of an "error prevention" network. Future functional neuroimaging studies are likely to reveal further details of the modular organization of the neural network subserving executive processes and the mechanisms by which individual components interact to maintain the tightly coordinated yet highly flexible activity that characterizes the normal human cognitive system." [Full Text] [In light of PCT, this paragraph may be better understood if "response conflict" is replaced with "conflict between control systems." ACC refers to the anterior cingulate cortex; IPL refers to the inferior parietal cortex.]

Cabeza R, Nyberg L.
Imaging cognition II: An empirical review of 275 PET and fMRI studies.
J Cogn Neurosci 2000 Jan;12(1):1-47
"Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space/motion, smell), imagery (object, space/motion), language (written/spoken word recognition, spoken/no spoken response), working memory (verbal/numeric, object, spatial, problem solving), semantic memory retrieval (categorization, generation), episodic memory encoding (verbal, object, spatial), episodic memory retrieval (verbal, nonverbal, success, effort, mode, context), priming (perceptual, conceptual), and procedural memory (conditioning, motor, and nonmotor skill learning). To identify consistent activation patterns associated with these cognitive operations, data from 412 contrasts were summarized at the level of cortical Brodmann's areas, insula, thalamus, medial-temporal lobe (including hippocampus), basal ganglia, and cerebellum. For perception and imagery, activation patterns included primary and secondary regions in the dorsal and ventral pathways. For attention and working memory, activations were usually found in prefrontal and parietal regions. For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions. For episodic memory encoding, consistently activated regions included left prefrontal and medial temporal regions. For episodic memory retrieval, activation patterns included prefrontal, medial temporal, and posterior midline regions. For priming, deactivations in prefrontal (conceptual) or extrastriate (perceptual) regions were consistently seen. For procedural memory, activations were found in motor as well as in non-motor brain areas. Analysis of regional activations across cognitive domains suggested that several brain regions, including the cerebellum, are engaged by a variety of cognitive challenges. These observations are discussed in relation to functional specialization as well as functional integration." [Abstract]

Hasegawa, Ryohei P., Blitz, Ari M., Geller, Nancy L., Goldberg, Michael E.
Neurons in Monkey Prefrontal Cortex That Track Past or Predict Future Performance
Science 2000 290: 1786-1789
"Although frontal cortex is thought to be important in controlling behavior across long periods of time, most studies of this area concentrate on neuronal responses instantaneously relevant to the current task. In order to investigate the relationship of frontal activity to behavior over longer time periods, we trained rhesus monkeys on a difficult oculomotor task. Their performance fluctuated during the day, and the activity of prefrontal neurons, even measured while the monkeys waited for the targets to appear at the beginning of each set of trials, correlated with performance in a probabilistic rather than a determinist manner: neurons reflected past or predicted future performance, much more than they reflected current performance. We suggest that this activity is related to processes such as arousal or motivation that set the tone for behavior rather than controlling it on a millisecond basis, and could result from ascending pathways that utilize slow, second-messenger synaptic processes.
...
The correlation of neuronal activity in the prefrontal cortex with general probabilities of behavior with significant time lags, rather than with the details of the current trial may provide the cortical neurophysiological function of ascending pathways such as the modulatory dopaminergic and/or noradrenergic pathways. Usher et al. (13) showed that the activity and synchrony of neurons in the locus coeruleus correlate with the monkey's performance. The ascending pathways are clearly important to prefrontal function. Subcortical aminergic areas project diffusely to prefrontal cortex and receive input from it (14). A few studies suggest a functional role for them on prefrontal activity: antagonists change the properties of prefrontal neurons in monkeys performing memory tasks (15-17); extracellular dopamine increases when a monkey performs a delayed alternation task, a classic task which has been shown to require the prefrontal cortex (18). Because these ascending systems work through second-messenger pathways, these synaptic effects can take place over minutes rather than the few milliseconds needed for direct short-term synaptic processes and may explain the time lags seen in our data (19). One can easily postulate that our "past" neurons receive feedback from the task-related neurons that accomplished the task, and we can also easily postulate that our "future" neurons feed forward to neurons that will be responsible for accomplishing the task. If those projections include a second-messenger step, then we would expect to see the delays that we have demonstrated.

The activity that we have demonstrated in the prefrontal cortex may set the tone for behavior in a general way, similar to that accomplished by stimulants, fatigue, enthusiasm, arousal, or other influences through ascending pathways. The critical result of these experiments is the demonstration of a tonic signal in prefrontal cortex that changes across minutes rather than milliseconds, and which predicts or tracks the probability of past or future success rather than the actual details of the behavior itself." [Full Text] [Note that perception is controlled; behavior is not controlled. This article is included to provide an example of gain.]

Usher, Marius, Cohen, Jonathan D., Servan-Schreiber, David, Rajkowski, Janusz, Aston-Jones, Gary
The Role of Locus Coeruleus in the Regulation of Cognitive Performance
Science 1999 283: 549-554
"Noradrenergic locus coeruleus (LC) neurons were recorded in monkeys performing a visual discrimination task, and a computational model was developed addressing the role of the LC brain system in cognitive performance. Changes in spontaneous and stimulus-induced patterns of LC activity correlated closely with fluctuations in behavioral performance. The model explains these fluctuations in terms of changes in electrotonic coupling among LC neurons and predicts improved performance during epochs of high coupling and synchronized LC firing. Cross correlations of simultaneously recorded LC neurons confirmed this prediction, indicating that electrotonic coupling in LC may play an important role in attentional modulation and the regulation of goal-directed versus exploratory behaviors." [Full Text] [Note that "exploratory behavior" is simply an interpretation of control.]

Bernard J. Baars, James Newman, J.G. Taylor
Neuronal mechanisms of consciousness:
A Relational Global Workspace framework.
(Pages 269-278 in S. Hameroff, A. Kaszniak, J. Laukes, Toward a Science of Consciousness II: The second Tucson discussions and debates. Cambridge, MA: MIT Press, 1998.)
"This paper explores a remarkable convergence of ideas and evidence, previously presented in separate places by its authors. That convergence has now become so persuasive that we believe we are working within substantially the same broad framework. Taylor’s mathematical papers on neuronal systems involved in consciousness dovetail well with work by Newman and Baars on the thalamocortical system, suggesting a brain mechanism much like the global workspace architecture developed by Baars (see references below). This architecture is relational, in the sense that it continuously mediates the interaction of input with memory. While our approaches overlap in a number of ways, each of us tends to focus on different areas of detail. What is most striking, and we believe significant, is the extent of consensus, which we believe to be consistent with other contemporary approaches by Weiskrantz, Gray, Crick and Koch, Edelman, Gazzaniga, Newell and colleagues, Posner, Baddeley, and a number of others. We suggest that cognitive neuroscience is moving toward a shared understanding of consciousness in the brain."
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"The brain stem-thalamocortical axis supports the state, but not the detailed contents of consciousness, which are produced by cortex." [Full Text]

On Site Link: Consciousness Research

John G. Taylor
Constructing the Relational Mind
PSYCHE, 4(10), June 1998
"The "relational mind" approach to the inner content of consciousness is developed in terms of various control structures and processing strategies and their possible neurobiological identifications in brain sites. This leads naturally to a division of consciousness into a passive and an active part. A global control structure for the "single strand" aspect of consciousness is proposed as the thalamo-nucleus reticularis thalami-cortex coupled system, which is related to experimental data on the electrical stimulation of awareness. Local control, in terms of excitatory transfer from pre-processing sites to posterior working memory regions, is supported by data on subliminal perception timing and disambiguation of poorly defined percepts. The inner content of consciousness is understood as arising from the resulting relational features between inputs and stored pre-processing and episodic memories. Strong analogies are drawn between emergent properties of the model and suggested properties of "raw feels", supporting the thesis that working memories are the initial sites for the emergence of phenomenal awareness, and the frontal lobes for its further adumbration in terms of higher cognitive processing, including the creation of self." [Full Text]

Cho SB, Baars BJ, Newman J.
A Neural Global Workspace Model for Conscious Attention.
Neural Netw 1997 Oct 1;10(7):1195-1206
"Considerable progress is being made in interdisciplinary efforts to develop a general theory of the neural correlates of consciousness. Developments of Baars' Global Workspace theory over the past decade are examples of this progress. Integrating experimental data and models from cognitive psychology, AI and neuroscience, we present a neurocognitive model in which consciousness is defined as a global integration and dissemination system - nested in a large-scale, distributed array of specialized bioprocessors - which controls the allocation of the processing resources of the central nervous system. It is posited that this global control is effected via cortical 'gating' of a strategic thalamic nucleus. The basic circuitry of this neural system is reasonably well understood, and can be modeled, to a first approximation, employing neural network principles." [Abstract]

Llinas R, Ribary U, Contreras D, Pedroarena C.
The neuronal basis for consciousness.
Philos Trans R Soc Lond B Biol Sci 1998 Nov 29;353(1377):1841-9
"Attempting to understand how the brain, as a whole, might be organized seems, for the first time, to be a serious topic of inquiry. One aspect of its neuronal organization that seems particularly central to global function is the rich thalamocortical interconnectivity, and most particularly the reciprocal nature of the thalamocortical neuronal loop function. Moreover, the interaction between the specific and non-specific thalamic loops suggests that rather than a gate into the brain, the thalamus represents a hub from which any site in the cortex can communicate with any other such site or sites. The goal of this paper is to explore the basic assumption that large-scale, temporal coincidence of specific and non-specific thalamic activity generates the functional states that characterize human cognition." [Abstract]

Cudeiro-Mazaira FJ, Rivadulla-Fernandez JC.
[The thalamus: a dynamic door to perception]
Rev Neurol 2002 Jan 16-31;34(2):121-30
"Far from behaving as a simple relay station, the thalamic circuits represent the framework on which to build a truly dynamic biological filter which can select the messages to reach the cortex according to their relevance and the behavioural state of the person. Such filtering implies the participation of many neurotransmitters which represent as many different systems. Outstanding amongst these are the groups formed by acetylcholine and nitric oxide axons arising from the brainstem, and corticofugal fibers which are sent back from the cortex to the thalamus." [Abstract]

Jones EG.
Viewpoint: the core and matrix of thalamic organization.
Neuroscience 1998 Jul;85(2):331-45
"The integration of the whole cerebral cortex and thalamus during forebrain activities that underlie different states of consciousness, requires pathways for the dispersion of thalamic activity across many cortical areas. Past theories have relied on the intralaminar nuclei as the sources of diffuse thalamocortical projections that could facilitate spread of activity across the cortex. A case is made for the presence of a matrix of superficially-projecting cells, not confined to the intralaminar nuclei but extending throughout the whole thalamus. These cells are distinguished by immunoreactivity for the calcium-binding protein, D28K calbindin, are found in all thalamic nuclei of primates and have increased numbers in some nuclei. They project to superficial layers of the cerebral cortex over relatively wide areas, unconstrained by architectonic boundaries. They generally receive subcortical inputs that lack the topographic order and physiological precision of the principal sensory pathways. Superimposed upon the matrix in certain nuclei only, is a core of cells distinguished by immunoreactivity for another calcium-binding protein, parvalbumin, These project in highly ordered fashion to middle layers of the cortex in an area-specific manner. They are innervated by subcortical inputs that are topographically precise and have readily identifiable physiological properties. The parvalbumin cells form the basis for sensory and other inputs that are to be used as a basis for perception. The calbindin cells, especially when recruited by corticothalamic connections, can form a basis for the engagement of multiple cortical areas and thalamic nuclei that is essential for the binding of multiple aspects of sensory experience into a single framework of consciousness." [Abstract]

Fernandez de Molina y Canas A.
[Thalamo-cortical system and consciousness]
An R Acad Nac Med (Madr) 2000;117(4):855-69; discussion 869-81
"After reviewing the concept of the specific and non specific thalamo-cortical systems, the connectivity of the relay and intralaminar nuclei is analyzed as well as the recent data concerning the chemical identity of thalamic neurones, the concept and distribution of "matrix" and "core" neurones and its functional role. The intrinsic electrical properties of thalamic neurones, its mode of discharge--depending of the membrane potential level--and its functional significance in the context of the brain's global activity are discussed. Of special interest are the studies on the effects of lesion of the relay and intralaminar nuclei as well as its repercussion in the interpretation of the sensory perception. After intralaminar nuclei lesion the individual is not aware of the information conveyed through the specific channels. It follows a discussion on the importance of the temporal and spatial mapping in the elaboration of perception and cognition. Due to the intrinsic electrical properties and the connectivity of thalamic neurones two groups of corticothalamic loops are generated, which resonate at a frequency of 40 Hz. The specific thalamo-cortical loops give the content of cognition and the non specific loop, the temporal binding required for the unity of the cognitive experience. Consciousness is then, a product of the resonant thalamo-cortical activity, and the dialogue between the thalamus and cortex, the process that generates subjectivity, the unique experience we all recognized as the existence of the "self"." [Abstract]

Balkin TJ, Braun AR, Wesensten NJ, Jeffries K, Varga M, Baldwin P, Belenky G, Herscovitch P.
The process of awakening: a PET study of regional brain activity patterns mediating the re-establishment of alertness and consciousness.
Brain 2002 Oct;125(Pt 10):2308-19
"Awakening from sleep entails rapid re-establishment of consciousness followed by the relatively slow (20-30 min later) re-establishment of alertness--a temporal dissociation that facilitates specification of the physiological underpinnings of each of these facets of the awakening process. H(2)(15)O PET was used to assess changes in regional cerebral blood flow (rCBF) upon awakening from stage 2 sleep. Cerebral blood flow (CBF) was most rapidly re-established in centrencephalic regions (e.g. brainstem and thalamus), suggesting that the reactivation of these regions underlies the re-establishment of conscious awareness. Across the ensuing 15 min of wakefulness, further increases in CBF were evident primarily in anterior cortical regions, suggesting that the dissipation of sleep inertia effects (post-awakening performance and alertness deficits) is effected by reactivation of these regions. Concomitant shifts in correlation patterns of regional brain activity across the post-awakening period [in particular, a waning negative correlation between prefrontal cortex and mesencephalic reticular formation (RF) activity, and a waxing positive correlation between prefrontal cortex and ventromedial caudate nucleus (CAUD) activity] suggest that the post-awakening reversal of sleep inertia effects may be mediated by more than mere reactivation--it may also involve the functional reorganization of brain activity. Conversely, stable post-awakening correlations--such as those found between the anterior cingulate cortex (ACC) and most other brain regions--may denote the pattern of functional connectivity that underlies consciousness itself." [Abstract]

Ergenzinger ER, Glasier MM, Hahm JO, Pons TP.
Cortically induced thalamic plasticity in the primate somatosensory system.
Nat Neurosci 1998 Jul;1(3):226-9
"The influence of cortical feedback on receptive field organization in the thalamus was assessed in the primate somatosensory system. Chronic and acute suppression of neuronal activity in primary somatosensory cortex resulted in a striking enlargement of receptive fields in the ventroposterior thalamus. This finding demonstrates a dramatic 'top-down' influence of cortex on receptive field size in the somatosensory thalamus. In addition, this result has important implications for studies of adult neuronal plasticity because it indicates that changes in 'higher-order' areas of the brain can trigger extensive changes in the receptive field characteristics of neurons located earlier in the processing pathway." [Abstract]

Guillery RW.
Anatomical evidence concerning the role of the thalamus in corticocortical communication: a brief review.
J Anat 1995 Dec;187 ( Pt 3):583-92
"Two distinct types of thalamic nucleus are proposed on the basis of the afferent fibres that they receive from ascending pathways and from the cerebral cortex. 'First order nuclei' receive primary afferent fibres, definable on the basis of their origin and their intrathalamic synaptic relationships, from ascending pathways. These nuclei receive corticothalamic afferents from pyramidal cells in cortical layer 6, which also send branches to the thalamic reticular nucleus and appear to have a modulatory function. 'Higher order nuclei' receive most or all of their 'primary afferents' from pyramidal cells in cortical layer 5. These resemble the ascending primary afferents in the first order nuclei in terms of fine structure, synaptic relationships and in lacking a branch to the thalamic reticular nucleus. The higher order nuclei also receive modulatory afferents from layer 6. It is proposed that the higher-order nuclei are largely concerned with transmitting information about the output of one cortical area to another cortical area, and that they are likely to play a key role in corticocortical communication and higher cortical functions." [Abstract]

McAlonan K, Brown VJ.
The thalamic reticular nucleus: more than a sensory nucleus?
Neuroscientist 2002 Aug;8(4):302-5
"Sensory information is routed to the cortex via the thalamus, but despite this sensory bombardment, animals must attend selectively to stimuli that signal danger or opportunity. Sensory input must be filtered, allowing only behaviorally relevant information to capture limited attentional resources. Located between the thalamus and cortex is a thin lamina of neurons called the thalamic reticular nucleus (Rt). The thalamic reticular nucleus projects exclusively to thalamus, thus forming an essential component of the circuitry mediating sensory transmission. This article presents evidence supporting a role for Rt beyond the mere relay of sensory information. Rather than operating as a component of the sensory relay, the authors suggest that Rt represents an inhibitory interface or "attentional gate," which regulates the flow of information between the thalamus and cortex. Recent findings have also implicated Rt in higher cognitive functions, including learning, memory, and spatial cognition. Drawing from recent insights into the dynamic nature of the thalamic relay in awake, behaving animals, the authors present a speculative account of how Rt might regulate thalamocortical transmission and ultimately the contents of consciousness." [Abstract]

Castro-Alamancos, Manuel A.
Role of Thalamocortical Sensory Suppression during Arousal: Focusing Sensory Inputs in Neocortex
J. Neurosci. 2002 22: 9651-9655
"The thalamus serves as a gate that regulates the flow of sensory inputs to the neocortex, and this gate is controlled by neuromodulators from the brainstem reticular formation that are released during arousal. We found recently that sensory-evoked responses are suppressed in the neocortex during arousal. This sensory suppression results from the activity-dependent depression of the thalamocortical connection caused by increased tonic firing of thalamocortical cells during arousal. In the present study, the functional consequences of thalamocortical suppression during arousal were investigated using the vibrissae system of rodents. The results show that thalamocortical suppression is associated with a strong reduction in the spread of sensory inputs through the cortex, thus reducing the size of sensory representations. In addition, when the responses of single cells to principal and adjacent whiskers are compared, the response to the adjacent whiskers was found to be strongly suppressed, much more so than that of principal whiskers. Consequently, the receptive fields of cortical neurons become more focused to the principal whisker. The results indicate that thalamocortical suppression during arousal serves to focus sensory inputs to their appropriate representations in neocortex, which may be computationally helpful for the spatial processing of sensory information." [Abstract]

Smythies J.
The functional neuroanatomy of awareness: with a focus on the role of various anatomical systems in the control of intermodal attention.
Conscious Cogn 1997 Dec;6(4):455-81
"This review considers a number of recent theories on the neural basis of consciousness, with particular attention to the theories of Bogen, Crick, Llinas, Newman, and Changeux. These theories allot different roles to various key brain areas, in particular the reticular and intralaminar nuclei of the thalamus and the cortex. Crick's hypothesis is that awareness is a function of reverberating corticothalamic loops and that the spotlight of intramodal attention is controlled by the reticular nucleus of the thalamus. He also proposed different mechanisms for attention and intention ("will"). The current review presents a new hypothesis, based on elements from these hypotheses, including intermodal attention and olfaction and pain, which may pose problems for Crick's original theory. This work reviews the possible role in awareness and intermodal attention and intention of the cholinergic system in the basal forebrain and the tegmentum; the reticular, the intralaminar, and the dorsomedial thalamic nuclei; the raphe and locus coeruleus; the reticular formation; the ventral striatum and extended amygdala; insula cortex, and other selected cortical, areas. Both clinical and basic research data are covered. The conclusion is reached that the brain may work by largely nonlinear parallel processing and much intramodal shifts of attention may be effected by intracortical, or multiple corticothalamic mechanisms (small local "flashlights" rather than one major "searchlight"). But this is constrained by the functional anatomy of the circuits concerned and waking "awareness" is modulated by the many "nonspecific" systems (cholinergic from the basal forebrain, noradrenergic from the locus coeruleus, dopaminergic from the substantia nigra and ventral tegmentum, and serotoninergic from the raphe). But the principal agents for intermodal attention shifts, the "searchlight," may be two key nuclei of the cholinergic system in the mesencephalon. Clinical loss of consciousness results from damage to these nuclei but not from damage to the cholinergic nucleus basalis of the basal forebrain." [Abstract]

Perry E, Walker M, Grace J, Perry R.
Acetylcholine in mind: a neurotransmitter correlate of consciousness?
Trends Neurosci 1999 Jun;22(6):273-80
"The cholinergic system is one of the most important modulatory neurotransmitter systems in the brain and controls activities that depend on selective attention, which are an essential component of conscious awareness. Psychopharmacological and pathological evidence supports the concept of a 'cholinergic component' of conscious awareness. Drugs that antagonize muscarinic receptors induce hallucinations and reduce the level of consciousness, while the nicotinic receptor is implicated as being involved in the mechanism of action of general (inhalational) anaesthetics. In degenerative diseases of the brain, alterations in consciousness are associated with regional deficits in the cholinergic system. In Alzheimer's disease (AD), there is a loss of explicit (more than implicit) memory and hypoactivity of cholinergic projections to the hippocampus and cortex, while the visual hallucinations experienced by subjects with Dementia with Lewy bodies (DLB) are associated with reductions in neocortical ACh-related activity. In Parkinson's disease, the additional loss of pedunculopontine cholinergic neurones, which control REM (rapid eye movement) sleep or dreaming, is likely to contribute to REM abnormalities, which also occur in DLB. Widespread basal-forebrain and rostral brainstem cholinergic pathways, which include converging projections to the thalamus, appear to be located strategically for generating and integrating conscious awareness. Alleviation of a range of cognitive and non-cognitive symptoms by drugs that modulate the cholinergic system, which are being developed for the treatment of AD and related disorders, could be caused by changes in consciousness." [Abstract]

Manuel A. Castro-Alamancos, and Maria E. Calcagnotto
High-Pass Filtering of Corticothalamic Activity by Neuromodulators Released in the Thalamus During Arousal: In Vitro and In Vivo
J Neurophysiol 85: 1489-1497, 2001.
"The thalamus is the principal relay station of sensory information to the neocortex. In return, the neocortex sends a massive feedback projection back to the thalamus. The thalamus also receives neuromodulatory inputs from the brain stem reticular formation, which is vigorously activated during arousal. We investigated the effects of two neuromodulators, acetylcholine and norepinephrine, on corticothalamic responses in vitro and in vivo. Results from rodent slices in vitro showed that acetylcholine and norepinephrine depress the efficacy of corticothalamic synapses while enhancing their frequency-dependent facilitation. This produces a stronger depression of low-frequency responses than of high-frequency responses. The effects of acetylcholine and norepinephrine were mimicked by muscarinic and alpha(2)-adrenergic receptor agonists and blocked by muscarinic and alpha-adrenergic antagonists, respectively. Stimulation of the brain stem reticular formation in vivo also strongly depressed corticothalamic responses. The suppression was very strong for low-frequency responses, which do not produce synaptic facilitation, but absent for high-frequency corticothalamic responses. As in vitro, application of muscarinic and alpha-adrenergic antagonists into the thalamus in vivo abolished the suppression of corticothalamic responses induced by stimulating the reticular formation. In conclusion, cholinergic and noradrenergic activation during arousal high-pass filters corticothalamic activity. Thus, during arousal only high-frequency inputs from the neocortex are allowed to reach the thalamus. Neuromodulators acting on corticothalamic synapses gate the flow of cortical activity to the thalamus as dictated by behavioral state." [Full Text]

Sturm W, Willmes K.
On the functional neuroanatomy of intrinsic and phasic alertness.
Neuroimage 2001 Jul;14(1 Pt 2):S76-84
"Intrinsic and phasic alertness are the most basic aspects of attention intensity probably constituting the basis for the more complex and capacity-demanding aspects of attention selectivity. Intrinsic alertness represents the cognitive control of wakefulness and arousal and is typically assessed by simple reaction time tasks without a preceding warning stimulus. Phasic alertness, in contrast, is called for in reaction time tasks in which a warning stimulus precedes the target, and it represents the ability to increase response readiness subsequent to external cueing. We report PET and fMRI data from both the literature and our own experiments to delineate the cortical and subcortical networks subserving alertness, sustained attention (as another aspect of attention intensity), and spatial orienting of attention. Irrespective of stimulus modality, there seems to exist a mostly right-hemispheric frontal, parietal, thalamic, and brain-stem network which is coactivated by alerting and orienting attentional demands. These findings corroborate both the hypothesis of a frontal modulation of brain-stem activation probably via the reticular nucleus of the thalamus and of a coactivation of the posterior attention system involved in spatial orienting by the anterior alerting network. Under conditions of phasic alertness there are additional activations of left-hemisphere frontal and parietal structures which are interpreted as basal aspects of attention selectivity rather than additional features of alerting." [Abstract]

Wolkenhauer O.
Mathematical modelling in the post-genome era: understanding genome expression and regulation--a system theoretic approach.
Biosystems 2002 Feb;65(1):1-18
"This paper introduces a mathematical framework for modelling genome expression and regulation. Starting with a philosophical foundation, causation is identified as the principle of explanation of change in the realm of matter. Causation is, therefore, a relationship, not between components, but between changes of states of a system. We subsequently view genome expression (formerly known as 'gene expression') as a dynamic process and model aspects of it as dynamic systems using methodologies developed within the areas of systems and control theory. We begin with the possibly most abstract but general formulation in the setting of category theory. The class of models realised are state-space models, input--output models, autoregressive models or automata. We find that a number of proposed 'gene network' models are, therefore, included in the framework presented here. The conceptual framework that integrates all of these models defines a dynamic system as a family of expression profiles. It becomes apparent that the concept of a 'gene' is less appropriate when considering mathematical models of genome expression and regulation. The main claim of this paper is that we should treat (model) the organisation and regulation of genetic pathways as what they are: dynamic systems. Microarray technology allows us to generate large sets of time series data and is, therefore, discussed with regard to its use in mathematical modelling of gene expression and regulation." [Abstract]

Gierer A.
Networks of gene regulation, neural development and the evolution of general capabilities, such as human empathy.
Z Naturforsch [C] 1998 Jul-Aug;53(7-8):716-22
"A network of gene regulation organized in a hierarchical and combinatorial manner is crucially involved in the development of the neural network, and has to be considered one of the main substrates of genetic change in its evolution. Though qualitative features may emerge by way of the accumulation of rather unspecific quantitative changes, it is reasonable to assume that at least in some cases specific combinations of regulatory parts of the genome initiated new directions of evolution, leading to novel capabilities of the brain. These notions are applied, in this paper, to the evolution of the capability of cognition-based human empathy. It is suggested that it has evolved as a secondary effect of the evolution of strategic thought. Development of strategies depends on abstract representations of one's own possible future states in one's own brain to allow assessment of their emotional desirability, but also on the representation and emotional evaluation of possible states of others, allowing anticipation of their behaviour. This is best achieved if representations of others are connected to one's own emotional centres in a manner similar to self-representations. For this reason, the evolution of the human brain is assumed to have established representations with such linkages. No group selection is involved, because the quality of strategic thought affects the fitness of the individual. A secondary effect of this linkage is that both the actual states and the future perspectives of others elicit vicarious emotions, which may contribute to the motivations of altruistic behaviour." [Abstract]

Lau HC, Rogers RD, Haggard P, Passingham RE.
Attention to intention.
Science. 2004 Feb 20;303(5661):1208-10.
"Intention is central to the concept of voluntary action. Using functional magnetic resonance imaging, we compared conditions in which participants made self-paced actions and attended either to their intention to move or to the actual movement. When they attended to their intention rather than their movement, there was an enhancement of activity in the pre-supplementary motor area (pre-SMA). We also found activations in the right dorsal prefrontal cortex and left intraparietal cortex. Prefrontal activity, but not parietal activity, was more strongly coupled with activity in the pre-SMA. We conclude that activity in the pre-SMA reflects the representation of intention." [Abstract]

Rowe J, Friston K, Frackowiak R, Passingham R.
Attention to action: specific modulation of corticocortical interactions in humans.
Neuroimage. 2002 Oct;17(2):988-98.
"The prefrontal cortex may exert cognitive control by a general mechanism of attentional selection of neuronal representations. We used functional magnetic resonance imaging to test this hypothesis in the motor system. Normal volunteers were scanned during performance of a simple motor task, with their attention either directed towards their actions, or diverted towards a visual search task, or neither. Attention to action increased activity in prefrontal, premotor and parietal cortex, compared with unattended performance of the same movements. Analysis of cortical activity by structural equation modelling of regional fMRI time series was used to measure effective connectivity among prefrontal, premotor and parietal cortices. Attention to action enhanced effective connectivity between dorsal prefrontal cortex and premotor cortex, whereas non-motor attention diminished it. These effects were not attributable to common inputs from parietal cortex to the prefrontal and premotor cortex. The results suggest a supra-modal role for the dorsal prefrontal cortex in attentional selection, operating within the motor system as well as sensory and mnemonic domains." [Abstract]

Jimura K, Konishi S, Miyashita Y.
Dissociable concurrent activity of lateral and medial frontal lobe during negative feedback processing.
Neuroimage. 2004 Aug;22(4):1578-86.
External feedback on results of one's behavior guides flexible adaptation to changing environments. It has been suggested that the lateral and medial parts of the frontal lobe are responsible for cognitive and emotional functions, respectively. In the present fMRI study, multiple mental components evoked by the presentation of negative feedback were dissociated along the cognitive-emotional axis in set-shifting paradigms. The double dissociation of the concurrent feedback-related activity was observed in the right frontal lobe: the lateral frontal lobe was associated with the inferential component, whereas the medial frontal lobe was associated with the emotional component. However, among the multiple right lateral frontal regions, a region of interest (ROI) analysis indicated that the inferential component was not dominant in the region near the inferior frontal junction. The medial frontal activations were observed ventral and anterior to the presupplementary motor area, and dorsal and posterior to the anterior cingulate cortex. The double dissociation in the right frontal lobe suggests that the lateral and medial frontal lobe cooperatively but differentially contributes to the negative feedback processing, demonstrating the lateral-medial dichotomy of the frontal lobe functions suggested by previous neuropsychological studies. At the same time, the functional heterogeneity in the lateral and medial frontal lobe demands modifications of the traditional view of the functional organization of the frontal lobe. [Abstract]