Relations of symptoms to cognitive deficits in schizophrenia.

Schizophrenia is characterized by a variety of cognitive dysfunctions. Information-processing dysfunctions differ between clinical subtypes such that nonparanoid schizophrenia patients attend less than paranoid schizophrenia patients to connotative or contextual aspects of stimuli. The positive and negative symptom dimensions are also associated with distinct cognitive deficits. In general, positive symptoms are related to auditory-processing deficits and negative symptoms to visual/motor dysfunctions. The interaction of frontal and septohippocampal brain systems, and failures of information-processing automaticity and self-monitoring, have been proposed as the bases of positive symptoms. Negative symptoms are thought to arise from abnormalities in the complex interactions of frontal and striatal systems. Recent theoretical analyses have recommended a focus on the cognitive and neuropsychological analysis of specific symptoms (e.g., hallucinations and delusions) instead of on the more heterogeneous symptom clusters or dimensions. Studies of specific symptoms indicate that patients with hallucinations have deficits in discriminating the source of information. Delusions have been related to abnormal inference processes as well as abnormal perceptual experiences. Studies should now examine the links between information-processing abnormalities and symptoms over time, as the latter change, within the framework of explicit, disconfirmable theoretical models.