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A crossmodal priming experiment was used to investigate lexical ambiguity resolution during sentence processing in individuals with nonthalamic
subcortical lesions (NSL) (n=10), compared to matched normal controls (n=10), and individuals with cortical lesions (CL) (n=10) and Parkinson's disease (PD) (n=10). Critical sentences biased toward the dominant or subordinate meaning of a sentence-final lexical ambiguity were presented auditorily, followed first by a short interstimulus interval (ISI) (0 msec) or a long ISI (1000 msec), and then by the presentation of a visual target that was either related to the dominant or subordinate meaning, or was an unrelated control word. Subjects made speedy lexical decisions on the targets. At the short ISI, lexical activation for the neurological patient groups appeared to be influenced by contextual information to a greater extent than in normal controls, which may indicate delayed lexical decision making or disturbed automatic lexical activation. At the long ISI, only the PD and NSL individuals failed to selectively activate the contextually appropriate meaning, suggesting a breakdown in the attention-based control of semantic activation through contextual integration. This finding may implicate disruptions to proposed frontal-striatal mechanisms that mediate attentional allocation and strategy formation.