There has been much debate over whether 'pure' prosopagnosia is possible, or if it always occurs alongside difficulties with other objects.
An area of the temporal lobe called the fusiform gyrus, also known as the fusiform face area, has been identified as specialising in face perception. However, an alternative view is that the area is involved in recognition of all kinds of objects. Recent research, published in the journal Neuropsychologia, provides strong evidence for pure prosopagnosia and for the fusiform gyrus' role in face recognition.
The study reported the case of a female patient known as PS, who sustained a TBI in 1992. One of the main brain regions PS injured was the left fusiform gyrus. PS recovered extremely well after undergoing rehabilitation and her one continuing problem is with recognising faces, including her own face in photographs. She identifies people using their haircuts, clothes, glasses or
facial hair.
Several previous studies have compared PS to normal participants on object and face recognition and found that she performs just as well in all categories except faces. Faces differ from most categories of objects in that they all have very similar structure and the differences are subtle. The latest study recreated this subtlety using computer simulations of objects. The computer created very minor differences between individual members of categories such as birds, shoes, cars and dogs. Again, PS performed as well or better than the control subjects with all objects.
In an additional experiment with computer morphed faces, PS made around 20% more errors than other participants. These results seem to confirm that injury to the fusiform gyrus can lead to selective impairment in face recognition, although such a specific difficulty does appear to be rare.
Reference
Busigny, T., Graf, M., Mayer, E. & Rossion, B. (2010) Acquired prosopagnosia as a face-specific disorder: Ruling out the general visual similarity account.Neuropsychologia, 48, 2051-2067.
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