Some aspects of language processing revealed through the analysis of acquired aphasia: the lexical system.

Acquired aphasia is the loss of some aspect of language processing consequent to brain damage. The specific form of aphasia observed in a patient is determined by the locus of cerebral insult. However, given the complexity of the language processing system, involving as it does complex linguistic mechanisms--phonological, lexical, syntactic, semantic, and pragmatic-as well as associated cognitive systems (e.g. working memory), a vast number of different forms of aphasia may be observed. Each form of aphasia observed is presumed to result from the particular type of damage to a component or combination of components of the language processing system. It is unrealistic, therefore, in the limited space available here, to attempt a review of the full range of possible language deficits in aphasia. A more managcable task is to focus the review on just one subsystem of the language faculty. This review focuses on the lexical system. Normally in a review I would at this point move directly to a presentation of the main theoretical and empirical developments in the area of lexical processing and the analysis of diverse forms of aphasia involving lexical deficits. However, developments over the past decade have led to a reconsideration of the theoretical and methodological underpinnings of the once dominant approach in neuropsyehological research, with the result that