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Context processing abnormalities may explain thought disorder in schizophrenia/schizotypy. This study aimed to assess predictive and integrative context processing in subjects with high or low scores on the Schizotypal Personality Questionnaire (SPQ). The N400 amplitude was recorded during semantic judgment of sentence pairs ending with a lateralized expected or unexpected word from the same or a different category (related and unrelated violation). In both groups, the N400 amplitude was less negative for expected words versus unrelated violations, regardless of which hemisphere received the stimulus, and for related versus unrelated violations, but only for left-hemisphere stimuli. The N400 amplitude for unrelated violations was less negative in subjects with high SPQ scores for both hemispheres. These results indicate that subjects with schizotypal traits use context to predict or integrate congruent words, but fail to inhibit incongruent words.

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Formal thought disorder is one of the major symptoms of schizophrenia and may be related to abnormal pattern of hemispheric lateralization of language functions. In accordance with recent neurolinguistic models that focus on the unique contribution of each hemisphere during language comprehension, the aim of this study is to explore the effect of schizotypy on hemispheric differences in semantic context processing.The task was a modified version of Federmeier and Kutas’ paradigm (1999). Subjects headed pairs of sentences ending with an expected exemplar, an unexpected exemplar from the same category, or an unexpected exemplar from a different category. Pairs of sentences were presented binaurally while the last word (target) was presented either at the left or at the right ear (the reversed target was presented to the contralateral ear). The subjects performed a semantic judgment task. Reaction times (RTs) and percentage of correct responses were recorded. The schizotypy was assessed using the Schizotypal Personality Questionnaire (SPQ, Raine et al., 1991).Results showed that although the two hemispheres were sensitive to semantic context, the left hemisphere strongly activated small semantic fields, whereas the right hemisphere weakly activated large semantic fields. The percentage of correct responses did not differ between the two hemispheres. In addition, subjects with higher SPQ scores demonstrated a lack of semantic context effect on the left hemisphere and a diffuse activation of concepts on the right hemisphere. The implication of these results in the understanding of the cognitive mechanisms of schizophrenic formal thought disorder is discussed.

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Abstract. A deficit in context processing may underlie theory of mind (ToM) difficulties in schizophrenia, although few studies to date have explored the impact of contextual processing on ToM performances within the same task. We used electroencephalography to investigate the production of intentional inferences from highly versus weakly structured sentences in healthy participants with schizotypal traits. Thirty-four participants were divided into two groups according to their scores on the Schizotypal Personality Questionnaire (SPQ). The participants listened to stories that required a degree of understanding in order to produce an inference about the main character’s intention. Each story was followed by a target word that could either be highly predictable (HP), weakly predictable (WP), or incompatible with the context. The results indicate that the N400 component for WP targets was stronger in the high-SPQ group. This increase correlated with the negative dimension of schizotypy. This may reflect difficulties with generating intentional inferences when the context is insufficiently structured for high schizotypy participants.