The Mapping of Sound Structure to the Lexicon:

Evidence from Lesion Studies and Neuroimaging

Sheila E. Blumstein

Brown University

This research explores how listeners map the properties of sound on to the lexicon (the mental dictionary) and investigates the neural basis of such processing. A series of experiments are discussed exploring the effects of phonological and acoustic-phonetic structure on lexical processing. Results from normal subjects suggest that:

• activation of the lexicon is graded,
• both phonological and acoustic-phonetic structure influence lexical activation,
• the prototypicality of an exemplar member of a phonetic category influences the degree of lexical activation, and
• acoustic-phonetic structure activates not only its lexical representation and lexical network but also the lexical representation and lexical-semantic network of its competitors.

Results from aphasic patients suggest that they have a processing impairment characterized by deficits in the dynamics of lexical activation. Broca’s aphasics appear to have an overall reduction in lexical activation resulting in processing impairments under conditions of lexical competition. In contrast, Wernicke’s aphasics appear to have an increase in lexical activation or a failure to inhibit lexical candidates. The potential neural systems underlying lexical activation will be considered.