The neuroanatomy of phenomenal vision: a psychological perspective

Somewhere in the visual system, phenomenal vision--the seeing of colors, brightness, depths, shades, and motion--is generated not only from the distribution of light on the retina, but also when the eyes are closed, in dreams, hallucinations, phosphenes, and (possibly) imagery. Whether these different forms of phenomenal vision share a common substrate although their origins are different (optical, mechanical, electrical, endogenous) is discussed in the light of evidence from neuropsychological and functional imaging studies. Whereas extrastriate visual cortical areas appear to be involved in all types of phenomenal vision that have been studied, the necessity of a contribution from primary visual cortex is demonstrated by the loss of conscious vision that follows its destruction. If both extrastriate and primary cortical activation are needed, the latter may not just provide an indispensable input, but may also need to receive the output of the extrastriate processing via reentrant connections.