Authors:

Graham, K. S., Becker, J. T., Patterson, K. & Hodges, J. R.

Reference:

Year of publication:

1997

CBU number:

3541

Abstract:

We describe a patient (GC) who presented with a history of progressive anomia (particularly for the names of people and objects) and difficulty understanding the meaning of previously familiar words. We investigated the nature of GC's naming problems: were they representative of semantic dementia or progressive pure anomia? Initially, there was a marked discrepancy between GC's ability to produce words (in spontaneous speech and in formal tests of picture naming) and his milder deficits on tests of semantic memory not involving speech production, a pattern which suggests any semantic impairment may have been exacerbated by an additional deficit in communication between semantic and phonological representations. Longitudinal testing revealed, however, progressive problems on tests of semantic memory, a result which suggests that GC's problems were predominantly at the level of semantic knowledge. GC's performance on semantic memory tests was also affected by modality of presentation: GC was much better on the Pyramid and Palm Trees Test when given pictures compared with words. A detailed study of GC's definitions to spoken words and pictures revealed that this discrepancy was not due to separate visually- and verbally-based semantic systems, but by an account in which both words and pictures activate more-or-less the same central conceptual representations. The apparent picture superiority is explained in terms of affordances present in the pictures, but not the words, for example, a picture of a bird-like animal "affords" the general inference that the creature can fly (an inference that is correct for most birds, but not all).