Ruth Condray - US grants

The linguistic style of many schizophrenics is a distinctive feature of their clinical picture, but the cognitive processes underlying the way in which this patient group uses language remain unclear. Semantic processing in normal individuals appears to involve at least two types of information processing: (a) processes that are automatic and rapid; and (b) processes that are controlled by the individual and require more time to engage. The locus of disturbance in the semantic processing of schizophrenics is currently unknown. The proposed study is designed to address two questions: (1) the locus of potential disturbance in schizophrenics' semantic processing (automatic versus controlled processes); and (2) the time-locked characteristics of schizophrenics semantic processing that occur after stimulus presentation and prior to response output (e.g., lever press). Psychophysiological (event-related potentials) and behavioral (reaction time) responses during the performance of a lexical decision task will be examined in 20 schizophrenic patients and 20 normal controls. Event-related potentials (ERP's) provide information not accessible with behavioral data (reaction time) by providing time-locked indicators of cognitive events that occur between stimulus presentation and response output. We hypothesize that schizophrenic patients will be characterized by disturbances in controlled semantic processing, but that they may exhibit normal automatic semantic processing. In addition, exploratory analyses will be conducted concerning the association of semantic processing and: (1) thought disorder; and (2) medication status.

There is increasing evidence that schizophrenics are characterized disturbances in the processing of linguistic context. However, the mechanism responsible for these disturbances remains unidentified. To date, studies have not incorporated methods for contrasting the underlying cognitive processes, such as the spreading activation and strategic-processing mechanisms. This investigation will test the hypothesis that a deficient strategic-processing mechanism produces these contextual processing difficulties through two approaches: (1) by measuring event-related potentials (ERPs) elicited during word recognition in a semantic priming task that assesses both spreading activation and strategic-processing mechanisms; and (2) by evaluating the association between the understanding of larger, more complex units of contextual information (syntactically complex sentences); and the ERP correlates of strategic-processing engaged during word recognition. This investigation will also determine whether these processes are modulated by schizophrenics' medication status. Language processing is highly relevant to the neuropathology of schizophrenia due to its functional association with brain systems implicated in recent neuroanatomical models of the disorder. Thus, elucidation of the mechanism(s) underlying schizophrenics' language disturbances will have significant bearing on our understanding of the neuropathology associated with the disorder. Disordered language is also associated with Schizotypal Personality Disorder (SPD), which is included among the schizophrenia-spectrum disorders. Schizophrenia-spectrum disorders may reflect the genotype for schizophrenia, with diagnosed schizophrenia the product of environmental trauma and neurological sequelae. Thus, a continuum of neurocognitive impairment is presumed to characterize the schizophrenia-spectrum. However, this hypothesized continuum remains largely untested because studies have not compared directly different populations of schizophrenia-spectrum disorders. This investigation will test this hypothesis by comparing the language processing of individuals diagnosed with Schizotypal Personality Disorder who differ on the basis of a family history of schizophrenia (i.e., with and without schizophrenic relatives). Clarification of this issue will have significant etiological implications, as well as contribute to our understanding of the neuropathology associated with the schizophrenia-spectrum disorders.

DESCRIPTION (Applicant's abstract): Disturbances in language function were among the first clinical observations reported for individuals described as schizophrenic, with selected aspects accorded preeminent theoretical status. Currently, language disturbances are among the constellation of hallmark symptoms that are diagnostic of the schizophrenia disorder. However, the linguistic conditions and psychological functions that contribute to schizophrenics' language dysfunction are not well understood and require elucidation. The focus of this revised application remains directed to the development of a theory that will explain the language processing disturbances of schizophrenia. The meaning embodied in discourse (i.e., connected language) is generally assumed to be realized through multiple layers of linguistic structures. Our model of language dysfunction in schizophrenia proposes that schizophrenic individuals are characterized by capacity limitations that influence their ability to use fully the contextual information that is conveyed through semantic and syntactic linguistic conventions. These capacity limitations exist at multiple levels, and produce dysfunctions that range from the processing of single words in small, discrete units of semantic context (lexical identification), to the processing of the logical relationships expressed in complex sentence structures. In the FIRST award project, schizophrenics showed a reduction in their ERP sensitivity to semantic context during lexical identification (ERP priming), which was only marginally improved during pharmacological treatment. A major finding was that the source of patients' compromised ERP priming was in their response to semantically associated contexts. Functions that were correlated with the accuracy of sentence comprehension included a sensitivity to word frequency information during lexical identification as well as a capacity to hold or maintain information while the semantic and syntactic parsing is accomplished. In contrast, sensitivity to type of semantic context during lexical identification (ERP priming) was not correlated with comprehension accuracy. The specific aims of the current proposal are: (1) To increase the specification of our model of language processing disturbance in schizophrenia, we will test hypotheses about the linguistic conditions and psychological functions that produce disruptions in schizophrenics' language processing. (2) To compare language processing between schizophrenic patients, family members of schizophrenic probands, and normal controls.