Tim Crane University College London 1. Introduction P.F. Strawson argued that ‘mature sensible experience (in general) presents itself as … an immediate consciousness of the existence of things outside us’ (1979: 97). He began his defence of this very natural idea by asking how someone might typically give a description of their current visual experience, and offered this example of such a description: ‘I see the red light of the setting sun filtering through the black and thickly clustered branches of (...) the elms; I see the dappled deer grazing in groups on the vivid green grass…’ (1979: 97). In other words, in describing experience, we tend to describe the objects of experience – the things which we experience – and the ways they are when we are experiencing them. (shrink)

The Cognitive Neuroscience of Vision begins by introducing the reader to the anatomy of the eye and visual cortex and then proceeds to discuss image and...

Awareness is a personal experience, which is only accessible to the rest of world through interpretation. We set out to identify a neural correlate of visual awareness, using brief subliminal and supraliminal verbal stimuli while measuring cerebral blood flow distribution with H215O PET. Awareness of visual verbal stimuli differentially activated medial parietal association cortex (precuneus), which is a polymodal sensory cortex, and dorsolateral prefrontal cortex, which is thought to be primarily executive. Our results suggest participation of these higher order perceptual (...) and executive cortical structures in visual verbal awareness. (shrink)

Logothetis, N.K.: Single units and conscious vision. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences 353, 1801-1818 (1998) Abstract.

This paper develops an empirically motivated theory of visual consciousness. It begins by outlining neuropsychological support for Jackendoff's (1987) hypothesis that visual consciousness involves mental representations at an intermediate level of processing. It then supplements that hypothesis with the further requirement that attention, which can come under the direction of high level representations, is also necessary for consciousness. The resulting theory is shown to have a number of philosophical consequences. If correct, higher-order thought accounts, the multiple drafts account, and the (...) widely held belief that sensation precedes perception will all be found wanting. The theory will also be used to illustrate and defend a methodology that fills the gulf between functionalists who ignore the brain and neural reductionists who repudiate functionalism. (shrink)

Stoerig links blindsight to lesions between the primary visual cortex and the extravisual cortex. A parallel 'blindsight' occurs when input from the primary visual cortex is blocked during eye movements, convergence and blinks. At such moments (i) conscious vision based upon retinal input is blocked, (ii), however, like in blind sight retinal input can be used in motor tasks. The main difference to blindsight is that we are not only blind but cannot even with deliberate attention bring this blindness into (...) awareness. We are doubly unaware: unaware of being blind and unaware that in spite of this that what we can see is created by the posterior parietal cortex substituting output (for that temporarily not coming from the primary visual cortex) for higher areas of the cerebral cortex. (shrink)

The visual brain consists of several parallel, functionally specialized processing systems, each having several stages (nodes) which terminate their tasks at different times; consequently, simultaneously presented attributes are perceived at the same time if processed at the same node and at different times if processed by different nodes. Clinical evidence shows that these processing systems can act fairly autonomously. Damage restricted to one system compromises specifically the perception of the attribute that that system is specialized for; damage to a given (...) node of a processing system that leaves earlier nodes intact results in a degraded perceptual capacity for the relevant attribute, which is directly related to the physiological capacities of the cells left intact by the damage. By contrast, a system that is spared when all others are damaged can function more or less normally. Moreover, internally created visual percepts-illusions, afterimages, imagery, and hallucinations-activate specifically the nodes specialized for the attribute perceived. Finally, anatomical evidence shows that there is no final integrator station in the brain, one which receives input from all visual areas; instead, each node has multiple outputs and no node is recipient only. Taken together, the above evidence leads us to propose that each node of a processing-perceptual system creates its own microconsciousness. We propose that, if any binding occurs to give us our integrated image of the visual world, it must be a binding between microconsciousnesses generated at different nodes. Since any two microconsciousnesses generated at any two nodes can be bound together, perceptual integration is not hierarchical, but parallel and postconscious. By contrast, the neural machinery conferring properties on those cells whose activity has a conscious correlate is hierarchical, and we refer to it as generative binding, to distinguish it from the binding that might occur between the microconsciousnesses. (shrink)

Among psychologists and vision scientists,binocular rivalry has enjoyed sustainedinterest for decades dating back to the 19thcentury. In recent years, however, rivalry''saudience has expanded to includeneuroscientists who envision rivalry as a tool for exploring the neural concomitants ofconscious visual awareness and perceptualorganization. For rivalry''s potential to berealized, workers using this tool need toknow details of this fascinating phenomenon,and providing those details is the purpose ofthis article. After placing rivalry in ahistorical context, I summarize major findingsconcerning the spatial characteristics and thetemporal dynamics (...) of rivalry, discuss two majortheoretical accounts of rivalry ( eye vs stimulus rivalry) and speculate on possibleneural concomitants of binocular rivalry. (shrink)

Binocular rivalry provides a useful situation for studying the relation between the temporal flow of conscious experience and the temporal dynamics of neural activity. After proposing a phenomenological framework for understanding temporal aspects of consciousness, we review experimental research on multistable perception and binocular rivalry, singling out various methodological, theoretical, and empirical aspects of this research relevant to studying the flow of experience. We then review an experimental study from our group explicitly concerned with relating the temporal dynamics of rivalrous (...) experience to the temporal dynamics of cortical activity. Drawing attention to the importance of dealing with ongoing activity and its inherent changing nature at both phenomenological and neurodynamical levels, we argue that the notions of recurrence and variability are pertinent to understanding rivalry in particular and the flow of experience in general. (shrink)

From Soul to Self takes us on a fascinating journey through philosophy, theology, religious studies and physiological sciences. The contributors explore the relationship between a variety of ideas that have arisen in philosophy, religion and science, each idea seeking to explain why we think we are somehow unique and distinct.

Traditional explanations of multistable visual phenomena (e.g. ambiguous figures, perceptual rivalry) suggest that the basis for spontaneous reversals in perception lies in antagonistic connectivity within the visual system. In this review, we suggest an alternative, albeit speculative, explanation for visual multistability – that spontaneous alternations reflect responses to active, programmed events initiated by brain areas that integrate sensory and non-sensory information to coordinate a diversity of behaviors. Much evidence suggests that perceptual reversals are themselves more closely related to the expression (...) of a behavior than to passive sensory responses: (1) they are initiated spontaneously, often voluntarily, and are influenced by subjective variables such as attention and mood; (2) the alternation process is greatly facilitated with practice and compromised by lesions in non-visual cortical areas; (3) the alternation process has temporal dynamics similar to those of spontaneously initiated behaviors; (4) functional imaging reveals that brain areas associated with a variety of cognitive behaviors are specifically activated when vision becomes unstable. In this scheme, reorganizations of activity throughout the visual cortex, concurrent with perceptual reversals, are initiated by higher, largely non-sensory brain centers. Such direct intervention in the processing of the sensory input by brain structures associated with planning and motor programming might serve an important role in perceptual organization, particularly in aspects related to selective attention. (shrink)

Might we be parts of a divine mind? Could anything like an afterlife make sense? Starting with a Platonic answer to why the world exists, Immortality Defended suggests we could well be immortal in all of three separate ways. Tackles the fundamental questions posed by our very existence, among them ‘why does the cosmos exist?’, ‘is there a divine mind or God?’ and ‘in what sense might we have afterlives?’ Defends a belief in immortality, without the need for a religious (...) affiliation or rejection of modern science Explores the ideas of ‘Einsteinian immortality’, the divine afterlife, and the theory of an infinite and divine mind Draws from the work of a wide-range of philosophers, from ancient Greece to the present day, and incorporates up-to-date scientific findings Written in a thought-provoking and engaging manner, accessible to anyone intrigued by the wonder of our being. (shrink)

In addressing thescientific study of consciousness, Crick and Koch state, It is probable that at any moment some active neuronal processes in your head correlate with consciousness, while others do not: what is the difference between them? (1998, p. 97). Evidence from electrophysiological and brain-imaging studies of binocular rivalry supports the premise of this statement and answers to some extent, the question posed. I discuss these recent developments and outline the rationale and experimental evidence for the interhemispheric switch hypothesis of (...) perceptual rivalry. According to this model, the perceptual alternations of rivalry reflect hemispheric alternations, suggesting that visual consciousness of rivalling stimuli may be unihemispheric at any one time (Miller et al., 2000). However, in this paper, I suggest that interhemispheric switching could involve alternating unihemispheric attentional selection of neuronal processes for access to visual consciousness. On this view, visual consciousness during rivalry could be bi hemispheric because the processes constitutive of attentional selection may be distinct from those constitutive of visual consciousness. This is a special case of the important distinction between the neuronal correlates and constitution of visual consciousness. (shrink)

Are humans composed of a body and a nonmaterial mind or soul, or are we purely physical beings? Opinion is sharply divided over this issue. In this clear and concise book, Nancey Murphy argues for a physicalist account, but one that does not diminish traditional views of humans as rational, moral, and capable of relating to God. This position is motivated not only by developments in science and philosophy, but also by biblical studies and Christian theology. The reader is invited (...) to appreciate the ways in which organisms are more than the sum of their parts. That higher human capacities such as morality, free will, and religious awareness emerge from our neurobiological complexity and develop through our relation to others, to our cultural inheritance, and, most importantly, to God. Murphy addresses the questions of human uniqueness, religious experience, and personal identity before and after bodily resurrection. (shrink)

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). (shrink)

This paper concentrates on the basic properties of ''consciousness'' that temporal coding is postulated to relate to. A description of phenomenal consciousness based on what introspection tells us about its contents is offered. This includes a consideration of the effect of various brain lesions that result in cortical blindness, apperceptive and associative agnosia, and blindsight, together with an account of the manner in which sight is regained after cortical injuries. I then discuss two therories of perception-Direct Realism and the Representative (...) Theory. This includes a discussion of the concept of the body-image, phantom limbs, the alleged projection of sensations, the ontological status of phenomenal space, the homunculus argument, the validity of topographic coding, the difference between the stimulus field and the visual field, and two theories of brain-mind relationship-the Identity Theory and the Bohr-Heisenberg theory of brain-mind complementarity. Finally I suggest that the binocular rivalry obtained in the case of the stroboscopic patterns that result from intermittent photic stimulation of one eye, when used in animal expeiments with unit recording, offers a good experimental method of investigating the binding problem. (shrink)

This is a brief account of a theory of presentiment/retrocausation in the context of a proposed binocular rivalry experiment. According to orthodox (classical or quantum mechanical) physics there can be no retrocausal effects. In order to accommodate such effects one must go beyond/outside orthodox theories. The simplest way to modify QM in a way that would permit such effects is to accept the hypothesis of Eccles (1987) that mental involvement (mental effort or emotion) can alter the orthodox statistical weighting factors (...) associated with the observed outcomes of our experimental probing actions. (shrink)

From the evolutionary viewpoint, animals need to monitor the surrounding environment and capture salient features, such as motion, for survival. The visual system is highly developed for monitoring a wide area of visual field and capturing such salient features. In humans and primates, there is a wide binocular field, suggesting a necessity of integrating the images from the two eyes. Binocular rivalry [R. Blake, A neural theory of binocular rivalry, Psychol. Rev. 96 (1989) 145–167; R. Blake, N.K. Logothetis, Visual competition, (...) Nat. Rev. Neurosci. 3 (2002) 13–21], where incompatible inputs from the two eyes compete to emerge in the subject’s visual percept, has been shown to exhibit highly adaptive behavior [I. Kovacs, T.V. Parathomas, M. Yang, A. Feher, When the brain changes its mind: interocular grouping during binocular rivalry. Proc. Natl. Acad. Sci. U.S.A. 93 (1996) 15508–15511; N.K. Logothetis, Single units and conscious vision, Philos. Trans. R. Soc. Lond. B. Biol. Sci. 353 (1998) 1801–1818]. Here we investigated the spatio-temporal dynamics of the ocular dominance pattern in binocular rivalry under conditions where conflicting salient features were presented in a temporally varying manner. We found a striking example of the detailed structure of the dominance wave propagation, by using a spatio-temporal sampling method. The data show in detail the ability of the visual system to dynamically adapt to the changing stimuli in the context of the massively parallel visual field. We show by model prediction that the globally coherent dominance change in the presence of multiple stimuli can be explained by a mechanism based on local saliency comparison. © 2005 Elsevier Ireland Ltd. All rights reserved. (shrink)