Abnormalities: Trait- and State-Dependent Components

Schizophrenics were compared to schizoaffective, bipolar, and nonpsy-chotic depressed patients in a visual masking paradigm in which an infor-mational target stimulus was followed at varying intervals by a noninformational masking stimulus. In limiting the availability of the sensory signal provided by the target stimulus, the mask was used to probe how information from the environ-ment enters and is processed by the central nervous system. The use of the masking paradigm was originally based on the hypothesis that thought disorder is a result of a more primary dysfunction in the processes that precede and result in thought. Results confirmed previous findings of a performance deficit in the schizo-phrenics when compared to nonpsy-chotic controls. Schizoaffective and bipolar patients also showed evidence of impaired processing, however. Results were interpreted in terms of a trait/state formulation in which impaired information processing is seen as a fundamental trait of schizo-phrenia spectrum disorders and as a state that can covary with psychotic illness in general. A unifying concept centers on the effects of psychopatho-logical conditions on an individual's processing resources that results in either underprovision or overpro-vision of information from sensory input to complex cognitive opera-tions dependent on the cerebral cortex. Findings from a variety of paradigms are consistent with those of the masking paradigm in revealing that the processing deficits of schizo-phrenics are time dependent and occur in the 500 ms following stimulus input. Formal thought disorder is a chief defining characteristic of the group of schizophrenic disorders. In this context, information-processing approaches to schizophrenia view thought as the product of a number of stages or processes, such as the selection of relevant information from the environment, elaboration and interpretation of input, and the transfer of information throughout the nervous system. Information-processing approaches to the schizo-phrenias attempt to isolate an abnormality in the processes that result in thought. It is this underlying attentional or information-processing abnormality, not thought per se, that is viewed as the basic cognitive dysfunction in schizophrenia