Multiple meaning systems in the brain: a case for visual semantics.

In this study we report our investigations of a category specific visual associative agnosia. The patient D.R.S.'s spoken language skills were excellent. Although he could name objects from their description, he was unable to name them by sight nor was he able to mime their use. On visual-visual matching tasks his performance was impaired and affected by semantic proximity. In two tasks his knowledge of visual objects was demonstrated to be significantly more impaired than his knowledge of visual living things. It is argued that these findings support a multiple knowledge base hypothesis.