Visual phenomenal consciousness: a neurological guided tour

The scientific study of the cerebral substrate of consciousness has been marked by significant recent achievements, resulting partially from an interaction between the exploration of cognition in both brain-damaged patients and healthy subjects. Several neuropsychological syndromes contain marked dissociations that permit the identification of principles related to the neurophysiology of consciousness. The generality of these principles can then be evaluated in healthy subjects using a combination of experimental psychology paradigms, and functional brain-imaging tools. In this chapter, I review some of the recent results relevant to visual phenomenal consciousness, which is an aspect of consciousness most frequently investigated in neuroscience. Through the exploration of neuropsychological syndromes such as “blindsight,” visual form agnosia, optic ataxia, visual hallucinations, and neglect, I highlight four general principles and explain how their generality has been demonstrated in healthy subjects using conditions such as visual illusions or subliminal perception. Finally, I describe the bases of a scientific model of consciousness on the basis of the concept of a “global workspace,” which takes into account the data reviewed.