The Neuronal Basis of Visual Consciousness

Abstract

Introduction: We outline in this chapter some of our present ideas about consciousness in general and visual consciousness in particular. For now, we believe that the most productive research strategy is to focus on the neuronal correlates of consciousness (NCC). The next step is to establish the exact nature of the causal relationship between neuronal events and subjective feelings and, finally, to understand the thorny philosophical problem of qualia or subjective feelings and how they can arise out of certain physical systems. We assume that higher mammals, such as rodents or primates, share certain forms of sensory consciousness with humans, even though these animals lack language skills. To characterize the NCC, we have to contrast neural activity that directly gives rise to conscious sensations, thoughts or action with neural activity that is associated with unconscious, stereotyped and on-line visuo-motor behavior. Where is the difference between these forms? How do these differences in activity relate to the ventral and dorsal streams? We emphasize the importance of explicit representations, the idea of essential nodes in a network and whether such nodes correspond to the columnar properties of a patch of cortex. We also discuss whether the correlated firing of a set of neurons is needed for consciousness and the role of cortical area V1 and prefrontal areas in consciousness. We end by briefly describing some of the relevant experiments. For earlier versions of these ideas, see (Crick and Koch, 1998 and Koch and Crick, 2000).

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