POSITIVE AND NEGATIVE SCHIZOPHRENIC SYMPTOMS AND SUSTAINED ATTENTION (PSYCHOSIS, COGNITION, PSYCHOPATHOLOGY)

This study was concerned with positive and negative schizophrenic symptom dimensions and their relationships with deficits in sustained attention, response bias, and the capacity to process information under conditions of information overload. Sixteen schizophrenic patients, rated for positive and negative symptomatology, 17 depressed patients, and 31 normal control subjects were tested on a measure of sustained attention and information processing capacity, the continuous performance task (CPT). To evaluate the validity of the version of the CPT used in the current study, schizophrenic patients were compared with depressed patients (psychiatric controls) and normal control subjects. Sustained attention deficits, as assessed both by standard CPT indices and an index of discriminability (d'), appeared specific to schizophrenic patients, while both the schizophrenic and depressed patients displayed evidence of a decreased capacity to process information under conditions of information overload. Among the schizophrenic patients, positive and negative symptom dimensions were found to be independent. Positive symptomatology was associated with deficits in sustained attention, whereas negative symptomatology was associated with lowered processing capacity. No association was found between either positive or negative symptoms and the signal detection index measuring response bias, suggesting that motivation was not an important factor in test performance. An examination of the relationships between specific positive or negative symptoms and selected CPT performance indices revealed that hallucinations and thought disorder were the positive symptoms most closely associated with deficits in sustained attention, whereas there was a trend suggesting avolition was the negative symptom most closely associated with lowered processing capacity. The symptomatology findings were interpreted as supporting two hypotheses: that positive symptomatology is related to attention deficits possibly mediated by dopaminergic transmission (Cornblatt, Lenzenweger, Dworkin, & Erlenmeyer-Kimling, 1985); as well as Crow's (1981) hypothesis that the two clinical syndromes reflect independent pathological processes.