Meaning selection and the subcortex: evidence of reduced lexical ambiguity repetition effects following subcortical lesions.

Recent research indicates that individuals with nonthalamic subcortical (NS) lesions can experience difficulties processing lexical ambiguities in a variety of contexts. This study examined how prior processing of a lexical ambiguity influences subsequent meaning activation in 10 individuals with NS lesions and 10 matched healthy controls. Subjects made speeded lexical decisions on related or unrelated targets following homophone primes. Homophones were repeated with different targets biasing the same or different meanings on the second presentation. The effects of prime-target relatedness interstimulus interval (200 or 1250 ms), and same vs. different meaning repetition were examined. Both the patient and control groups showed priming when the same homophone meaning was biased on repetition. When a different meaning was biased on the second presentation, no priming was evident in the controls, while facilitation remained present for the NS group, consistent with aberrant meaning selection and deactivation processes. These findings are discussed in terms of age and task-related repetition effects and current conceptions of frontal-subcortical involvement in cognition.