Automatic versus controlled priming in individuals with schizophrenia

Speech that is disturbed in form and structure, called formal thought disorder, is a primary symptom of schizophrenia. In trying to understand thought disorder in individuals with schizophrenia, researchers have proposed at least three ways in which deficits in the semantic memory system, (memory for words, their meanings, and associations) may be associated with the language deficits seen in these individuals. Specially, three types of semantic system deficits have been hypothesized to lead to thought disorder in individuals with schizophrenia; (1) degraded storage, (2) abnormal spreading activation, and (3) impaired strategic access. Semantic priming paradigms have long been used to assess access to, and the integrity and organization of, the semantic system. However, the results from such studies in individuals with schizophrenia have been mixed, with some results consistent with each of the hypotheses outlined above. In addition, few priming studies in individuals with schizophrenia have been explicitly designed to compare and contrast these different hypotheses. In this dissertation I propose to compare these three hypotheses about semantic system disturbances leading to disorganized speech in individuals with schizophrenia. I tested these hypotheses by conducting a study of semantic priming in individuals with schizophrenia and community controls using a lexical decision task that allows me to assess the integrity of both automatic spreading activation and expectancy processes. The task manipulates the expectancy of prime-target pairs at three different stimulus onset asynchronies (250 ms, 1750 ms, and 3250 ms). I predict that using a paradigm that allows for each of the above hypotheses to be examined in the same study will help clarify the integrity of the semantic system in individuals with schizophrenia. Specifically, based on evidence from a recent meta analysis of the literature examining cognitive impairments in schizophrenia (Kerns & Berenbaum, 2002) 1 predict that priming performance by individuals with schizophrenia will demonstrate intact storage and normal spreading activation, and that the results of the lexical decision task will be consistent with the hypothesis of impaired strategic access.