A hallmark characteristic of thought disorder in schizophrenia is contextual insensitivity. We propose to test the hypothesis that impaired contextual inhibition, but not contextual facilitation, is the primary mechanism of contextual insensitivity in schizophrenia using a semantic priming paradigm. In our version of this technique, subjects listen to sentence primes containing ambiguous words (e.g., pen), and see targets presented for a lexical decision response (i.e., word/nonword judgment) that are semantically related to dominant (e.g., paper) or subordinate (e.g., pig) meanings. Experiments 1a and 1b test the effects of semantic constraint and processing time on contextual facilitation and inhibition in schizophrenic patients (n=65), normal controls (n=40), and non- schizophrenic psychiatric controls (n=40). In Experiment 1a, sentence contexts will be neutral, and moderately and strongly biased towards the subordinate meaning of an ambiguous words. Visual targets will immediately follow the acoustic offset of the sentence prime (i.e., 0 ms stimulus onset asynchrony) Experiment 1b will be identical to Experiment 1a except that the visual target will be presented 1000 ms following the acoustic offset of the sentence prime (i.e., 1000 ms stimulus onset asynchrony) to provide additional time to process the context. Schizophrenic patients are predicted to show (1) impaired contextual inhibition for contextually irrelevant dominant meanings in moderate subordinate-biased contexts, (2) intact contextual facilitation of subordinate meanings for moderate and strong subordinate-biased contexts, (3) appropriate increases in contextual inhibition accompanying increases in contextual strength, and (4) increased contextual inhibition and facilitation given additional time to process the context. In addition, performance on the language task will be examined with respect to independent measures of thought disorder (i.e., each participant's total Thought Disorder Index (TDI) score and Deviant Verbalization subscore of the TDI) and cognitive inhibition (e.g., performance on the Stroop interference task, the negative priming task, and the antisaccade task). The results of this work will provide a clearer understanding of the cognitive mechanisms underlying contextual insensitivity in schizophrenia. Thus they will inform theories of contextual processing and inhibitory dysfunction in schizophrenia that are applicable to a wide array of neurocognitive tasks.
