Researchers from London and Italy have just published a study on the brain areas involved in perceiving and understanding faces. They created an elegant experiment where they used morphing to compare how brain activity changes as a photograph is gradually blended from one person to another, for example, from Marilyn Monroe to Margaret Thatcher.
They found that the brain did not respond in the same gradual manner, and that activation shifted to specific areas at certain points in the blending process. When the blending was in its early stages, participants perceived the picture as the same person with physical changes to their face, an experience which caused activation in the inferior occipital gyrus. When the level of blending affected recognition of the pictured person, the right fusiform gyrus was activated, an area thought to be involved with judgements of familiarity for faces. When a participant was already familiar with the people in the pictures, the temporal lobes became active when the final face became clear. These areas have been linked to semantic memory and naming.
This study is important as it shows specialised areas of activation for different stages in the face perception process in a single experiment.
These stages have been hypothesised to exist for quite some time in a model developed by psychologists Vicki Bruce and Andy Young, largely from studies on people with prosopagnosia, a condition where face recognition can be impaired, usually after brain damage.