Abstract: 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

Abstract: The binding problem is to explain how information processed by different sensory systems is brought together to unify perception. The problem has two sides. First, we want to explain phenomenal binding: the fact that we experience a single world rather than separate perceptual fields for each sensory modality. Second, we must solve a functional problem: to explain how a neural net like the brain links instances to types. I argue that phenomenal binding and functional binding require very different treatments. The puzzle of phenomenal binding rests on a confusion and so can be dissolved. So only functional binding deserves explanation. The general solution to that problem is that information to be bound is arrayed along different dimensions. So sensory coding into separate topographic maps facilitates functional binding and there is no need based on the unity of perception for special mechanisms that bring "back together" information in different maps

Abstract: Several of the essays in this collection discuss the `binding problem', the problem of explaining in neurophysiological terms how it is that we see the various perceptual qualities of a physical object, such as its shape, colour, location and motion, as features of a single object. The perceived object seems to us a unitary thing, but its sensory properties are diverse and turn out to be processed in different areas of the brain. How then does the brain manage the integration? Readers of the essays in this collection may find themselves suffering from an analogous binding problem about the study of consciousness, though this problem is conceptual rather than perceptual, and here the difficulty is to achieve the integration rather than to understand how an effortless integration is achieved. Consciousness is the ideal topic for inter-disciplinary investigation. It is a central concern of such diverse disciplines as neurophysiology, evolutionary biology, psychology, cognitive science, philosophy and theology, among others, yet none of these disciplines has come close to providing full answers to the central questions that consciousness raises. Inter-disciplinary investigation seems an obvious way forward, but it generates the conceptual binding problem that this collection displays. The standard of the essays is very high, but it is extraordinarily difficult to integrate their content into anything like a single picture. We are all apparently talking about the same phenomenon, the conscious awareness of the world that each of us enjoys first-hand, but it is quite unclear how to see the very different things we say about this phenomenon as part of a single picture, or even as parts of different but compatible pictures. Having raised the binding problem for the inter-disciplinary study of consciousness, I hasten to say that I will not attempt even a partial substantive solution here: that is left as an exercise for the readers of this book.

Abstract: Laboratoire de Neurosciences Cognitives et Imagerie Ce´re´brale (LENA), Hoˆpital de La Salpeˆtrie`re, Centre National de la Recherche Scientifique (CNRS)

Abstract: Temporal binding via 40-Hz synchronization of neuronal discharges in sensory cortices has been hypothesized to be a necessary condition for the rapid selection of perceptually relevant information for further processing in working memory. Binocular rivalry experiments have shown that late stage visual processing associated with the recognition of a stimulus object is highly correlated with discharge rates in inferotemporal cortex. The hippocampus is the primary recipient of inferotemporal outputs and is known to be the substrate for the consolidation of working memories to long-term, episodic memories. The prefrontal cortex, on the other hand, is widely thought to mediate working memory processes, per se. This article reviews accumulated evidence for the role of a subcortical matrix in linking frontal and hippocampal systems to select and ''stream'' conscious episodes across time (hundreds of milliseconds to several seconds). ''Streaming'' is hypothesized to be mediated by the selective gating of reentrant flows of information between these cortical systems and the subcortical matrix. The physiological mechanism proposed for this temporally extended form of binding is synchronous oscillations in the slower EEG spectrum (< 8 Hz)

Abstract: The binding problem is frequently discussed in consciousness research. However, it is by no means clear what the problem is supposed to be and how exactly it relates to consciousness. In the present paper the nature of the binding problem is clarified by distinguishing between different formulations of the problem. Some of them make no mention of consciousness, whereas others are directly related to aspects of phenomenal experience. Certain formulations of the binding problem are closely connected to the classical philosophical problem of the unity of consciousness and the currently fashionable search for the neural correlates of consciousness. Nonetheless, only a part of the current empirical research on binding is directly relevant to the study of consciousness. The main message of the present paper is that the science of consciousness needs to establish a clear theoretical view of the relation between binding and consciousness and to encourage further empirical work that builds on such a theoretical foundation

Abstract: (von der Malsburg, 1981), “the binding problem” has with the visual percept of it, so that both are effortlessly captured the attention of researchers across many disci- perceived as being aspects of a single event. I like to plines, including psychology, neuroscience, computa- refer to these sorts of problems as perceptual binding tional modeling, and even philosophy. Despite the is- problems, since they involve unifying aspects of per- sue’s prominence in these fields, what “binding” means cepts. In addition, there are cognitive binding problems: is rarely made explicit. In this paper, I will briefly survey they include relating a concept to a percept, such as the many notions of binding and will introduce some linking the visual representation of an apple to all the issues that will be explored more fully in the reviews semantic knowledge stored about it (it is edible, how it that follow

Abstract: How do our brains represent distinct objects in consciousness? In order to consciously distinguish between objects, our brains somehow selectively bind together activity patterns of spatially intermingled neurons that simultaneously represent similar and dissimilar features of distinct objects. Gamma-band synchronous oscillations (GSO) of neuroelectrical activity have been hypothesized to be a mechanism used by our brains to generate and bind conscious sensations to represent distinct objects. Most experiments relating GSO to specific features of consciousness have been published only in the last several years. This brief review focuses on a wide variety experiments in which animals, including humans, discriminate between sensory stimuli and make these discriminations evident in their behavior. Performance of these tasks, in humans, is invariably accompanied by conscious awareness of both stimuli and behavior. Results of these experiments indicate that specific patterns of GSO correlate closely with specific aspects of conscious sensorimotor processing. That is, GSO appear to be closely correlated with neural generation of our most paradigmatic cognitive state: consciousness

Abstract: Recent experiments have shown that the amplitudes of cortical gamma band oscillatory activities that occur during anesthesia are often greater than amplitudes of similar activities that occur without anesthesia. This result is apparently at odds with the hypothesis that synchronized oscillatory activities constitute the neural correlate of consciousness. We argue that while synchronization and oscillatory patterning are necessary conditions for consciousness, they are not sufficient. Based on the results of a binocular rivalry study of Fries et al. (1997), we propose that the degrees of oscillatory strength and synchronization of neuronal activities determine the degree of awareness those activities produce. On the other hand, the overal firing rates of neurons in cortical sensory areas are not correlated with the degree of awareness the activities of those neurons produce. The results of the experiment of Fries et al. (1997) appear to conflict with the results of another binocular rivalry experiment, in which monkeys were trained to pull a lever in order to report which stimulus object was being perceived (Leopold & Logothetis, 1996). In the latter experiment, it was demonstrated that the firing rates of neurons in striate cortex did not change during perceptual alterations, while 90% of neurons in inferior and superior temporal cortices changed their firing rate when the perceived image changed. This result led to the conclusion that activities in temporal cortex are correlated with visual awareness, but those in striate cortex are not. We argue that activities in temporal cortex contribute little, if anything, to perceptual awareness, and that their primary function is computational. Thus the correlation between the firing rates of neurons in these areas and the responses of the monkeys is due to the recognition of a particular stimulus object, which in turn is due to the computations made there