Apperceptive agnosia and face recognition

Are faces and objects recognized by separate visual recognition systems or might a single system subserve the recognition of both classes of input? Re cognition of faces and objects by a single system predicts that prosopagnos ics, who selectively lose the ability to recognize faces due to brain damag e, should also lose the ability to recognize objects. Contrary to this pred iction, case studies of prosopagnosia have reported intact object recogniti on. Further support for separate visual recognition systems comes from the case of HH reported here. Following a stroke involving the left posterior c ortex, HH has a severe apperceptive visual agnosia for visually presented o bjects and an alexia for words. Yet, he shows relatively spared visual face processing. Such a performance pattern completes a double dissociation bet ween face and object processing when coupled with prosopaganosia. More impo rtantly, HH is the first apperceptive visual object agnosic to demonstrate spared face processing. The severity of his object-processing deficit is su ch that from the earliest levels in the visual processing hierarchy, distin ct neural substrates must be responsible for processing some objects and fa ces. These results are discussed as support for Farah's model (Visual agnos ia: disorders of object recognition and what they tell us about normal visi on. Cambridge, MA: MIT Press, 1990) of object, face and word recognition.