Neurocognitive Functioning in Patients with Schizophrenia: an Overview

Increasingly, neurocognitive paradigms are used to study patients with schizophrenia. With such paradigms, the cognitive abnormalities in schizophrenia are characterized by means of experimental and clinical tests. These techniques have indicated that some types of cognitive impairment are not only reliably present in schizophrenia, but are also central and enduring features of the disease. This chapter, a revision of the one published in 1995, focuses on certain recent advances in characterizing the precise nature of cognitive impairments in schizophrenia, on understanding the implications of these for treatment given the course and relationship to outcome of these variables, and on novel applications of neurocognitive approaches to the genetics of schizophrenia. Cognitive abnormalities were noted by early investigators of schizophrenia. In the original clinical descriptions of schizophrenia made by Kraepelin (64), he commented, ‘‘Mental efficiency is always diminished to a considerable degree. The patients are distracted, inattentive . . . they cannot keep the thought in mind.’’ Some years later, Shakow (95) began a series of studies in which he examined abnormalities in patients’ reaction time in response to different types of readiness information and imperative stimuli. Hunt and Cofer (54) noted the intellectual quotient (IQ) of schizophrenic patients to be lower than that of normal controls. However, the increasing influence of psychodynamic theory tended to minimize the significance of the cognitive deficits of schizophrenia. It was thought that the deficits displayed on formal psychologic testing were secondary to impaired motivation or cooperation, gross breakdowns in reality testing, or disordered thought processes.