Chaos theory is a rapidly growing field. As a technical term, chaos refers to deterministic but unpredictable processes being sensitively dependent upon initial conditions. Neurobiological models and experimental results are very complicated and some research groups have tried to pursue the neuronal chaos. Babloyantz's group has studied the fractal dimension (d) of electroencephalograms (EEG) in various physiological and pathological states. From deep sleep (d=4) to full awakening (d>8), a hierarchy of strange attractors paralles the hierarchy of states of consciousness. In (...) epilepsy (petit mal), despite the turbulent aspect of a seizure, the attractor dimension was near to 2. In Creutzfeld-Jacob disease, the regular EEG activity corresponded to an attractor dimension less than the one measured in deep sleep. Is it healthy to be chaotic? An active desynchronisation could be favourable to a physiological system. Rapp's group reported variations of fractal dimension according to particular tasks. During a mental arithmetic task, this dimension increased. In another task, a P300 fractal index decreased when a target was identified. It is clear that the EEG is not representing noise. Its underlying dynamics depends on only a few degrees of freedom despite yet it is difficult to compute accurately the relevant parameters.What is the cognitive role of such a chaotic dynamics? Freeman has studied the olfactory bulb in rabbits and rats for 15 years. Multi-electrode recordings of a few mm2 showed a chaotic hierarchy from deep anaesthesia to alert state. When an animal identified a previously learned odour, the fractal dimension of the dynamics dropped off (near limit cycles). The chaotic activity corresponding to an alert-and-waiting state seems to be a field of all possibilities and a focused activity corresponds to a reduction of the attractor in state space. For a couple of years, Freeman has developed a model of the olfactory bulb-cortex system. The behaviour of the simple model without learning was quite similar to the real behaviour and a model with learning is developed. (shrink)

William James described the stream of thought as having two components: (1) a nucleus of highly conscious, often perceptual material; and (2) a fringe of dimly felt contextual information that controls the entry of information into the nucleus and guides the progression of internally directed thought. Here I examine the neural and cognitive correlates of this phenomenology. A survey of the cognitive neuroscience literature suggests that the nucleus corresponds to a dynamic global buffer formed by interactions between different regions of (...) the brain, while the fringe corresponds to a set of mechanisms in the frontal and medial temporal lobes that control the contents of this global buffer. A consequence of this account is that there might be conscious imagistic representations that are not part of the nucleus. I argue that phenomenology can be linked to psychology and neuroscience and a meaningful way that illuminates both. (shrink)

Theories of binding have recently come into the focus of the consciousness debate. In this review, we discuss the potential relevance of temporal binding mechanisms for sensory awareness. Specifically, we suggest that neural synchrony with a precision in the millisecond range may be crucial for conscious processing, and may be involved in arousal, perceptual integration, attentional selection and working memory. Recent evidence from both animal and human studies demonstrates that specific changes in neuronal synchrony occur during all of these processes (...) and that they are distinguished by the emergence of fast oscillations with frequencies in the gamma-range. (shrink)

It is proposed that attention to an object requires the simultaneous activity of three brain regions that are interconnected by a triangular circuit. The regions are the cortical site of attentional expression, the thalamic enhancement structure, and the prefrontal area of control. It is also proposed that awareness of an object requires the additional component of attention directed to a representation of the self. The expression of attention to a self-representation may involve activations of cortical sites corresponding to the body (...) landscape and/or verbal-based memories of autobiographical episodes. As in the case of attention to objects, attention to the self is presumed to involve a triangular circuit. The proposed triangular circuit of attention is shown to be generally consistent with current knowledge of brain structures and with data from a broad range of experiments concerned with the functions of neurons in these structures. (shrink)

Human agents draw a variety of inferences effortlessly, spontaneously, and with remarkable efficiency – as though these inferences were a reflexive response of their cognitive apparatus. Furthermore, these inferences are drawn with reference to a large body of background knowledge. This remarkable human ability seems paradoxical given the complexity of reasoning reported by researchers in artificial intelligence. It also poses a challenge for cognitive science and computational neuroscience: How can a system of simple and slow neuronlike elements represent a large (...) body of systemic knowledge and perform a range of inferences with such speed? We describe a computational model that takes a step toward addressing the cognitive science challenge and resolving the artificial intelligence paradox. We show how a connectionist network can encode millions of facts and rules involving n-ary predicates and variables and perform a class of inferences in a few hundred milliseconds. Efficient reasoning requires the rapid representation and propagation of dynamic bindings. Our model (which we refer to as SHRUTI) achieves this by representing (1) dynamic bindings as the synchronous firing of appropriate nodes, (2) rules as interconnection patterns that direct the propagation of rhythmic activity, and (3) long-term facts as temporal pattern-matching subnetworks. The model is consistent with recent neurophysiological evidence that synchronous activity occurs in the brain and may play a representational role in neural information processing. The model also makes specific psychologically significant predictions about the nature of reflexive reasoning. It identifies constraints on the form of rules that may participate in such reasoning and relates the capacity of the working memory underlying reflexive reasoning to biological parameters such as the lowest frequency at which nodes can sustain synchronous oscillations and the coarseness of synchronization. (shrink)

Many current neurophysiological, psychophysical, and psychological approaches to vision rest on the idea that when we see, the brain produces an internal representation of the world. The activation of this internal representation is assumed to give rise to the experience of seeing. The problem with this kind of approach is that it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness. An alternative proposal is made here. We propose that seeing is a way of (...) acting. It is a particular way of exploring the environment. Activity in internal representations does not generate the experience of seeing. The out- side world serves as its own, external, representation. The experience of seeing occurs when the organism masters what we call the gov- erning laws of sensorimotor contingency. The advantage of this approach is that it provides a natural and principled way of accounting for visual consciousness, and for the differences in the perceived quality of sensory experience in the different sensory modalities. Sev- eral lines of empirical evidence are brought forward in support of the theory, in particular: evidence from experiments in sensorimotor adaptation, visual “filling in,” visual stability despite eye movements, change blindness, sensory substitution, and color perception. (shrink)

Title page Representational theories propose a set of sufficient conditions for a state to be phenomenally conscious. It turns out that insofar as these conditions have been worked out in detail, the autonomic nervous system (ANS) ought to be conscious - but of course it’s not. In this paper, we’ll describe only a tiny portion of the complexities of the ANS, using these to counterexample only a single theory of phenomenal consciousness, namely, Fred Dretske’s. But we think the ANS comparison (...) strategy is a fruitful one in general, and we hope to convince you of this too. (shrink)

This paper provides evidence for the following novel insights: (1) People’s economic decisions depend on their psychological motives, which are shaped predictably by the social context. (2) In particular, the social context influences people’s other-regarding preferences, their beliefs and their perceptions. (3) The influence of the social context on psychological motives can be measured experimentally by priming two antagonistic motives—care and anger—in one player towards another by means of an observance or a violation of a fairness norm. Using a mediation (...) approach, we find that the care motive leads to higher levels of cooperation which are driven by more optimistic beliefs, a different perception of the game as well as by a shift towards more pro-social preferences. (shrink)

Theorists of oppression commonly accept that unfair social power disparities result in a variety of harms. In particular, oppression is characterized by a loss of open-mindedness in the oppressors, and negative internalization in the oppressed. That is, while oppressors are often unable or unwilling to consider the points of view of the oppressed, the oppressed often come to internalize conditions of oppression by experiencing them as indicative of their own alleged shortcomings. Nevertheless, the psychological mechanisms behind these phenomena have remained (...) underexplored. This is unfortunate, since understanding the psychological processes behind these phenomena could help us understand how they could be reversed. In this work, I aim to fill this lacuna by extending debates on mechanisms of mindreading to show how close-mindedness and negative internalization come about. I synthesize empirical findings to show that while theorizing fosters emotional insulation by “reframing” affective cues from a third-person point of view, simulation fosters feelings of emotional vulnerability and psychological continuity. As a result, while theorizing allows oppressors to take a somewhat detached attitude during self and other interpretation, involuntary simulation fosters negative internalization on the part of the oppressed. (shrink)

Life, whatsoever it is, is a temporal flux. Everything is doomed to change often apparently beyond our awareness. My body appears totally different now, so does my mind. I have gained new attitudes and new ambitions, and a substantial number of old ones have been discarded. But, I am still the same person in an ongoing manner. Besides, recent neuroscientific and psychological evidence has shown that our conscious perception happens as a series of discrete or bounded instants—it emerges in temporally (...) scattered, gappy, and discrete forms. But, if it is so, how does the brain persevere our self-continuity in this gappy setting? How is it possible that despite moment-to-moment changes in my appearance and mind, I am still feeling that I am that person? How can we tackle with this second by second gap and resurrection in our existence which leads to a foundation of wholeness and continuity of our self? How is continuity of self that results in a feeling that one’s life has purpose and meaning preserved? To answer these questions, the problem has been comprehended from a philosophical, psychological, and neuroscientific perspective. I realize that first and foremost fact lies in the temporal nature of identity. Having equipped with these thoughts, in this article, it is hypothesized that according to two principles self-continuity is maintained. It is supposed that there should be a precise temporal integration mechanism in the CNS with the outside world that provides us this smooth, ungappy flow of the Self. However, we are often taken for granted the importance of self-continuity, but it can be challenged by life transitions such as entering adulthood, retirement, senility, emigration, and societal changes such as immigration, globalization, and in much unfortunate and extreme cases of mental illnesses such as schizophrenia. (shrink)

By the late 1990s, several converging trends in economics, psychology, and neuroscience had set the stage for the birth of a new scientific field known as “neuroeconomics”. Without the availability of an extensive variety of experimental designs for dealing with individual and social decision-making provided by experimental economics and psychology, many neuroeconomics studies could not have been developed. At the same time, without the significant progress made in neuroscience for grasping and understanding brain functioning, neuroeconomics would have never seen the (...) light of day. The paper is an overview of the main significant advances in the knowledge of brain functioning by neuroscience that have contributed to the emergence of neuroeconomics and its rise over the past two decades. These advances are grouped over three non-independent topics referred to as the “emo-rational” brain, “social” brain, and “computational” brain. For each topic, it emphasizes findings considered as critical to the birth and development of neuroeconomics while highlighting some of prominent questions about which knowledge should be improved by future research. In parallel, it shows that the boundaries between neuroeconomics and several recent sub-fields of cognitive neuroscience, such as affective, social, and more generally, decision neuroscience, are rather porous. (shrink)

About one third of patients with epilepsy have seizures refractory to the medical treatment. Electrical stimulation mapping is the gold standard for the identification of “eloquent” areas prior to resection of epileptogenic tissue. However, it is time-consuming and may cause undesired side effects. Broadband gamma activity recorded with extraoperative electrocorticography during cognitive tasks may be an alternative to ESM but until now has not proven of definitive clinical value. Considering their role in cognition, the alpha and beta bands could further (...) improve the identification of eloquent cortex. We compared gamma, alpha and beta activity, and their combinations for the identification of eloquent cortical areas defined by ESM. Ten patients with intractable focal epilepsy participated in a delayed-match-to-sample task, where syllable sounds were compared to visually presented letters. We used a generalized linear model approach to find the optimal weighting of each band for predicting ESM-defined categories and estimated the diagnostic ability by calculating the area under the receiver operating characteristic curve. Gamma activity increased more in eloquent than in non-eloquent areas, whereas alpha and beta power decreased more in eloquent areas. Diagnostic ability of each band was close to 0.7 for all bands but depended on multiple factors including the time period of the cognitive task, the location of the electrodes and the patient’s degree of attention to the stimulus. We show that diagnostic ability can be increased by 3–5% by combining gamma and alpha and by 7.5–11% when gamma and beta were combined. We then show how ECoG power modulation from cognitive testing can be used to map the probability of eloquence in individual patients and how this probability map can be used in clinical settings to optimize ESM planning. We conclude that the combination of gamma and beta power modulation during cognitive testing can contribute to the identification of eloquent areas prior to ESM in patients with refractory focal epilepsy. (shrink)

In debates about animal sentience, the precautionary principle is often invoked. The idea is that when the evidence of sentience is inconclusive, we should “give the animal the benefit of the doubt” or “err on the side of caution” in formulating animal protection legislation. Yet there remains confusion as to whether it is appropriate to apply the precautionary principle in this context, and, if so, what “applying the precautionary principle” means in practice regarding the burden of proof for animal sentience. (...) Here I construct a version of the precautionary principle tailored to the question of animal sentience together with a practical framework for implementing it. I explain and defend the key features of this framework, argue that it is well-aligned with current practice in animal welfare science, and consider and reject a number of influential counterarguments to the use of precautionary reasoning in this area. (shrink)

Our primary goal in this article is to discuss the cross-talk between biological and cultural factors that become manifested in the individual brain development, neural wiring, neurochemical homeostasis, and behavior. We will show that behavioral propensities are the product of both cultural and biological factors and an understanding of these interactive processes can provide deep insights into why people behave the way they do. This interdisciplinary perspective is offered in an effort to generate dialog and empirical work among scholars interested (...) in merging aspects of anthropology and neuroscience, and anticipates that biological and cultural anthropology converge. We discuss new theoretical developments, hypothesis-testing strategies, and cross-disciplinary methods of observation and data collection. We believe that the exigency of integrating anthropology and the neurosciences is indisputable and anthropology's role in an emerging interdisciplinary science of human behavior will be critical because its focus is, and has always been, on human biological and cultural systems. (shrink)

Six keynote papers presented at TSC 2009 — by Susan Greenfield, Wolf Singer, Stuart Hameroff, Jonathan Schooler, Hakwan Lau, and David Chalmers—are reviewed below in order to investigate to what extent social analysis can be usefully applied in different areas of consciousness studies. The six papers did not ostensibly address social aspects of consciousness; nevertheless I hope to show that it is often beneficial to consider the possible social implications in any consciousness- related work.

Therehasbeenevidencefortheverybrief,temporalquantizationofperceptualexperienceatregularintervalsbelo w100msforseveraldecades.Webrieflydescribehowearlierstudiesledtotheconceptof“psychologicalmoment”ofbe tween50and60msduration.Accordingtohistoricaltheories,withinthepsychologicalmomentalleventswouldbepro cessedasco-temporal.Morerecently,alinkwithphysiologicalmechanismshasbeenproposed,accordingtowhichthe 50–60mspsychologicalmomentwouldbedefinedbytheupperlimitrequiredbyneuralmechanismstosynchronizeandthe rebyrepresentasnapshotofcurrentperceptualeventstructure.However,ourownexperimentaldevelopmentsalsoid entifyamorefine-scaled,serializedprocessstructurewithinthepsychologicalmoment.Ourdatasuggeststhatnot alleventsareprocessedasco-temporalwithinthepsychologicalmomentandinstead,someareprocessedsuccessivel y.Thisevidencequestionstheanalogrelationshipbetweensynchronizedprocessandsimultaneousexperienceandop ensdebateontheontologyandfunctionof“moments”inpsychologicalexperience.

Perception is a first-person internal sensation induced within the nervous system at the time of arrival of sensory stimuli from objects in the environment. Lack of access to the first-person properties has limited viewing perception as an emergent property and it is currently being studied using third-person observed findings from various levels. One feasible approach to understand its mechanism is to build a hypothesis for the specific conditions and required circuit features of the nodal points where the mechanistic operation of (...) perception take place for one type of sensation in one species and to verify it for the presence of comparable circuit properties for perceiving a different sensation in a different species. The present work explains visual perception in mammalian nervous system from a first-person frame of reference and provides explanations for the homogeneity of perception of visual stimuli above flicker fusion frequency, the perception of objects at locations different from their actual position, the smooth pursuit and saccadic eye movements, the perception of object borders, and perception of pressure phosphenes. Using results from temporal resolution studies and the known details of visual cortical circuitry, explanations are provided for (a) the perception of rapidly changing visual stimuli, (b) how the perception of objects occurs in the correct orientation even though, according to the third-person view, activity from the visual stimulus reaches the cortices in an inverted manner and (c) the functional significance of well-conserved columnar organization of the visual cortex. A comparable circuitry detected in a different nervous system in a remote species-the olfactory circuitry of the fruit fly Drosophila melanogaster-provides an opportunity to explore circuit functions using genetic manipulations, which, along with high-resolution microscopic techniques and lipid membrane interaction studies, will be able to verify the structure-function details of the presented mechanism of perception. (shrink)

The concept of empathy has received much attention from philosophers and also from both cognitive and social psychologists. It has, however, been given widely conflicting definitions, with some taking it primarily as an epistemological notion and others as a social one. Recently, empathy has been closely associated with the simulationist approach to social cognition and, as such, it might be thought that the concept’s utility stands or falls with that of simulation itself. I suggest that this is a mistake. Approaching (...) the question of what empathy is via the question of what it is for, I claim that empathy plays a distinctive epistemological role: it alone allows us to know how others feel. This is independent of the plausibility of simulationism more generally. With this in view I propose an inclusive definition of empathy, one likely consequence of which is that empathy is not a natural kind. It follows that, pace a number of empathy researchers, certain experimental paradigms tell us not about the nature of empathy but about certain ways in which empathy can be achieved. I end by briefly speculating that empathy, so conceived, may also play a distinctive social role, enabling what I term ‘transparent fellow-feeling’. (shrink)

Following the pragmatic practices of anesthesiologists an individual is defined to be in a state of consciousness empirically by the behavioral ability to respond to simple stimuli and the loss of consciousness is defined by the loss of that facility. Several brain activities are proposed as properties of the state of consciousness. Baseline brain energy consumption has been shown by 13C MRS to be almost completely used for neuronal signaling. PET measurements of glucose or oxygen consumption, from several laboratories, show (...) a widespread ~45% reduction in cerebral energy during anesthesia-induced loss of consciousness. We propose that the high level of brain energy consumption of the awake state is a necessary property of the state of consciousness. Two additional neuronal properties are drastic changes in the patterns of fMRI activation and neuronal population activity at deep vs. light levels of anesthesia, which correspond to low vs. high energy states, respectively. The brain-wide fMRI activity patterns with rat sensory stimulation at the higher energy state collapses to contralateral somatosensory response at the lower energy state. Firing rates of an ensemble of neurons in the rat somatosensory cortex show that most of the energy in light anesthesia is consumed in the spiking frequency range of 20-40 Hz, which include γ-band electrical signals. In deep anesthesia the frequency range shifts to below 10 Hz. The high brain energy consumption, characteristic of the state of consciousness, supports elevated levels of high frequency neuronal firing observed in the resting, awake brain. In our model, necessary brain properties of the state of consciousness create our physical understanding of that state rather than the converse, popular in neuroimaging, in which subjective mental processes are identified to be necessary and sufficient correlates of the state of consciousness. (shrink)

We suggest a common ground for alternative proposals In different domains of cognitive science which have previously seemed to have little in common. The underlying common theme is associated with a redefinition of the basic unit of analysis in each domain of thought. Our framework suggests a definition of unity which is based not on inherent properties of the elements constituting the unit, but rather on dynamic patterns of correlation across the elements. We introduce a set of features that characterize (...) the new dynamic units, and distinguish them from traditional units of analysis. A conceptual connection is made with the identification of elementary units in modern physics theories, as well as with concepts and structures in the study of complex dynamical systems and connectionism. The paper analyses the evolution of the concept of unit in different domains of thought in cognitive science, and examines the proposed framework of “dynamic unity” with regard to various theoretical problems within each domain. The particular cognitive science issues discussed in the paper include: (1) the binding problem in the brain; (2) the mental unit of conceptual organization; (3) defining ‘wordhood’ in linguistics; and (4) identifying the unit of cognition in the natural environment. (shrink)

The notion of empathy has been explicated in different ways in the current debate on how to understand others. Whereas defenders of simulation-based approaches claim that empathy involves some kind of isomorphism between the empathizer’s and the target’s mental state, defenders of the phenomenological account vehemently deny this and claim that empathy allows us to directly perceive someone else’s mental states. Although these views are typically presented as being opposed, I argue that at least one version of a simulation-based approach—the (...) account given by de Vignemont and Jacob—is compatible with the direct-perception view. My argument has two parts: My first step is to show that the conflict between these accounts is not—as it seems at first glance—a disagreement on the mechanism by which empathy comes about. Rather, it is due to the fact that their proponents attribute two very different roles to empathy in understanding others. My second step is to introduce Stein’s account of empathy. By not restricting empathy to either one of these two roles, her process model of empathy helps to see how the divergent intuitions that have been brought forward in the current debate could be integrated. (shrink)

Abstract Advances in technology now make it possible to monitor the activity of the human brain in action, however crudely. As this emerging science continues to offer correlations between neural activity and mental functions, mind and brain may eventually prove to be one. If so, such a full comprehension of the electrochemical bases of mind may render current concepts of ethics, law, and even free will irrelevant. Content Type Journal Article Category Original Paper Pages 1-5 DOI 10.1007/s11948-012-9351-1 Authors Thomas R. (...) Scott, San Diego State University, San Diego, California, USA Journal Science and Engineering Ethics Online ISSN 1471-5546 Print ISSN 1353-3452. (shrink)

This paper assesses the so-called “direct-perception” model of empathy. This model draws much of its inspiration from the Phenomenological tradition: it is offered as an account free from the assumption that most, if not all, of another’s psychological states and experiences are unobservable and that one’s understanding of another’s psychological states and experiences are based on inferential processes. Advocates of this model also reject the simulation-based approach to empathy. I first argue that most of their criticisms miss their target because (...) they are directed against the simulation-based approach to mindreading. Advocates of this model further subscribe to an expressivist conception of human behavior and assume that some of an individual’s psychological states (e.g. her goals and emotions, not her beliefs) can be directly perceived in the individual’s expressive behavior. I argue that advocates of the direct-perception model face the following dilemma: either they embrace behaviorism or else they must recognize that one could not understand another’s goal or emotion from her behavior alone without making contextual assumptions. Finally, advocates of the direct-perception model endorse the narrative competency hypothesis, according to which the ability to ascribe beliefs to another is grounded in the ability to understand narratives. I argue that this hypothesis is hard to reconcile with recent results in developmental psychology showing that preverbal human infants seem able to ascribe false beliefs to others. (shrink)

The philosophical world is indebted to Alvin Goldman for a number of reasons, and among them, his defense of the relevance of cognitive science for philosophy of mind. In "Simulating minds", Goldman discusses with great care and subtlety a wide variety of experimental results related to mindreading from cognitive neuroscience, cognitive psychology, social psychology and developmental psychology. No philosopher has done more to display the resourcefulness of mental simulation. I am sympathetic with much of the general direction of Goldman's theory. (...) I agree with him that mindreading is not a single system based on a single mechanism. And I admire his attempt to being together the cognitive neuroscientific discovery of mirror system phenomena and the philosophical account of pretense within a unique theoretical framework of mental simulation. To do so, Goldman distinguishes two types of mindreading, respectively, based on low-level and high-level simulation. Yet, I wonder in what sense they are really two distinct processes. Here, I will confine myself largely to spelling out a series of points that take issue with the distinction between low-level and high-level mindreading. (shrink)

This is a bibliography of books and articles on consciousness in philosophy, cognitive science, and neuroscience over the last 30 years. There are three main sections, devoted to monographs, edited collections of papers, and articles. The first two of these sections are each divided into three subsections containing books in each of the main areas of research. The third section is divided into 12 subsections, with 10 subject headings for philosophical articles along with two additional subsections for articles in cognitive (...) science and neuroscience. Of course the division is somewhat arbitrary, but I hope that it makes the bibliography easier to use. This bibliography has first been compiled by Thomas Metzinger and David Chalmers to appear in print in two philosophical anthologies on conscious experience . From 1995 onwards it has been continuously updated by Thomas Metzinger, and now is freely available as a PDF-, RTF-, or HTML-file. This bibliography mainly attempts to cover the Anglo-Saxon and German debates, in a non-annotated, fully formatted way that makes it easy to "cut and paste" from the original file. To a certain degree this bibliography also contains items in other languages than English and German - all submissions in other languages are welcome. Last update of current version: July 13th, 2001. (shrink)

This article provides a retrospective, current and prospective overview on developments in brain research and neuroscience. Both theoretical and empirical studies are considered, with emphasis in the concept of multivariability and metastability in the brain. In this new view on the human brain, the potential multivariability of the neuronal networks appears to be far from continuous in time, but confined by the dynamics of short-term local and global metastable brain states. The article closes by suggesting some of the implications of (...) this view in future multidisciplinary brain research. (shrink)

By using preimplantation haplotype diagnosis, prospective parents are able to select embryos to implant through in vitro fertilization. If we knew that the naturally-occurring (but theoretical) MoralKinder (MK+) haplotype would predispose individuals to a higher level of morality than average, is it permissible or obligatory to select for the MK+ haplotype? I.e., is it moral to select for morality? This paper explores the various potential issues that could arise from genetic moral enhancement.

For scene analysis, it is important to ask the question of how synchronized population codes – the basic representation employed in the target article – are generated. Recent computational advances have resolved the critical challenges of rapid synchronization with local coupling and rapid desynchronization. The synchronized codes make real contributions to tackling the problem of scene analysis.

Before one can talk about global arrays and multimodal detection, one must be clear about the concept of information: How is it different from energy and how is it detected? And can it come to specify a needed movement? We consider these issues in our commentary.

In attempts to formulate a computational understanding of brain function, one of the fundamental concerns is the data structure by which the brain represents information. For many decades, a conceptual framework has dominated the thinking of both brain modelers and neurobiologists. That framework is referred to here as "classical neural networks." It is well supported by experimental data, although it may be incomplete. A characterization of this framework will be offered in the next section. Difficulties in modeling important functional aspects (...) of the brain on the basis of classical neural networks alone have led to the recognition that another, general mechanism must be invoked to explain brain function. That mechanism I call " binding." Binding by neural signal synchrony had been mentioned several times in the liter ature before it was fully formulated as a general phenomenon. Although experimental evidence for neural syn chrony was soon found, the idea was largely ignored for many years. Only recently has it become a topic of animated discussion. In what follows, I will summarize the nature and the roots of the idea of binding, especially of temporal binding, and will discuss some of the objec tions raised against it. (shrink)

We tested the hypothesis that perception of an alternative image in ambiguous figures would be manifest as high-frequency (gamma) components that become synchronized over multiple scalp sites as a ''cognitive binding'' process occurs. For 171 combinations of data from 19 electrodes, obtained from 17 subjects and 10 replicate stimuli, we calculated the difference in correlation between the response to first seeing an ambiguous figure and when the alternative percept for that figure became consciously realized (cognitively bound). Numerous statistically significant correlation (...) differences occurred in all frequency bands tested with ambiguous-figure stimulation, but not in two kinds of control data (a reaction-time test to sound stimuli and a no-task, mind-wandering test). Statistically significant correlation changes were widespread, involving frontal, parietal, central, and occipital regions of both hemispheres. Correlation changes were evident at each of five frequency bands, ranging up to 62.5 Hz. Most of the statistically significant correlation changes were not between adjacent sites but between sites relatively distant, both ipsilateral and contralateral. Typically, these correlation changes occurred in more than one frequency band. These results suggest that cognitive binding is a distinct mental state that is reliably induced by ambiguous-figure perception tasks. Coherent oscillations at multiple frequencies may reflect the mechanism by which such binding occurs. Moreover, different coherent frequencies may mediate different components of the total cognitive-binding process. (shrink)

It has been shown that visual awareness in the blind hemifield of hemianopic cats that have undergone unilateral ablations of visual cortex can be restored by sectioning the commissure of the superior colliculus or by destroying a portion of the substantia nigra contralateral to the cortical lesion (the Sprague effect). We propose that the visual awareness that is recovered is due to synchronized oscillatory activities in the superior colliculus ipsilateral to the cortical lesion. These oscillatory activities are normally partially suppressed (...) by the inhibitory, GABAergic contralateral nigrotectal projection, and the destruction of the substantia nigra, or the sectioning of the collicular commissure, disinhibits the collicular neurons, causing an increase in the extent of oscillatory activity and/or synchronization between activities at different sites. This increase in the oscillatory and synchronized character is sufficient for the activities to give rise to visual awareness. We argue that in rodents and lower vertebrates, normal visual awareness is partly due to synchronized oscillatory activities in the optic tectum and partly due to similar activities in visual cortex. It is only in carnivores and primates that visual awareness is wholly due to cortical activities. Based on von Baerian recapitulation theory, we propose that, even in humans, there is a period in early infancy when visual awareness is partially due to activities in the superior colliculus, but that this awareness gradually disappears as the nigrotectal projection matures. (shrink)

Cognitive functions like perception, memory, language, or consciousness are based on highly parallel and distributed information processing by the brain. One of the major unresolved questions is how information can be integrated and how coherent representational states can be established in the distributed neuronal systems subserving these functions. It has been suggested that this so-called ''binding problem'' may be solved in the temporal domain. The hypothesis is that synchronization of neuronal discharges can serve for the integration of distributed neurons into (...) cell assemblies and that this process may underlie the selection of perceptually and behaviorally relevant information. As we intend to show here, this temporal binding hypothesis has implications for the search of the neural correlate of consciousness. We review experimental results, mainly obtained in the visual system, which support the notion of temporal binding. In particular, we discuss recent experiments on the neural mechanisms of binocular rivalry which suggest that appropriate synchronization among cortical neurons may be one of the necessary conditions for the buildup of perceptual states and awareness of sensory stimuli. (shrink)

It remains a dogma in cognitive neuroscience to separate human attention and memory into distinct modules and processes. Here we propose that brain rhythms reflect the embedded nature of these processes in the human brain, as evident from their shared neural signatures: gamma oscillations (30–90 Hz) reflect sensory information processing and activated neural representations (memory items). The theta rhythm (3–8 Hz) is a pacemaker of explicit control processes (central executive), structuring neural information processing, bit by bit, as reflected in the (...) theta-gamma code. By representing memory items in a sequential and time-compressed manner the theta-gamma code is hypothesized to solve key problems of neural computation: (1) attentional sampling (integrating and segregating information processing), (2) mnemonic updating (implementing Hebbian learning), and (3) predictive coding (advancing information processing ahead of the real time to guide behavior). In this framework, reduced alpha oscillations (8–14 Hz) reflect activated semantic networks, involved in both explicit and implicit mnemonic processes. Linking recent theoretical accounts and empirical insights on neural rhythms to the embedded-process model advances our understanding of the integrated nature of attention and memory – as the bedrock of human cognition. (shrink)