Brain areas specific for conscious visual experience have been identified.

A major challenge in neuroscience is to identify neurons whose activity maps specifically to conscious experience – the so-called neural correlates of consciousness. Using an artificially created form of blindsight, Hakwan Lau and Richard Passingham have pinpointed localised brain activity correlated with conscious visual experience.

Blindsight is the remarkable phenomenon whereby some people with specific brain damage have no conscious perception of a visual stimulus, but if forced to guess – by pointing to its location on a screen, for example – they are correct far more often than chance would dictate. The brain seems to register the stimulus even though it is not consciously perceived.

Lau and Passingham re-created this phenomenon in normal subjects using the technique of 'masking' – subjects were presented with a visual stimulus followed almost immediately by a second that partially obscured the first image. They were then forced to say what they thought the image was, even if they could not consciously recall it.

Although masking did not completely obliterate conscious perception, the researchers were able to identify and compare individuals who scored the same on the recognition test but had conscious awareness. Differences in brain activity therefore reflected differences in conscious awareness rather than detection of the visual stimulus.

The key area in the prefrontal cortex, the 'thinking' part of the brain. Although not down to neuron-level resolution, the work locates the site of conscious visual experience to a relatively small area of the brain.

External link

• Lau HC, Passingham RE. Relative blindsight in normal observers and the neural correlate of visual consciousness. Proc Natl Acad Sci USA 2006;103(49):18763–8.