Recent studies of psychophysiology in schizophrenia.

Eye movement dysfunctions have been shown to be reliably associated with schizophrenia as a trait, suggesting disorders of nonvoluntary attention in association with those brain areas involved in smooth pursuit and saccadic eye movements. The familial distributions of the eye movement dysfunction and of schizophrenia, when considered together, suggest the existence of a latent trait whose transmission fits an autosomal dominant transmission mode. Chronic schizophrenic patients show diminished variation and shorter latencies of early components of somatosensory brain related potentials, which reflect stimulus registration, and investigators have interpreted the finding as indicating impaired modulation of stimulus input, which allows too much information to reach higher brain centers. Laterality differences, in which the left hemisphere may be less efficient than the right, have also been reported. Schizophrenic patients show reduced amplitudes of later component waves of event related potentials, a finding that has been interpreted as reflecting impaired selective attention. The issue of whether these deviations are state or trait related has not yet been resolved. Directed attention in the form of vigilance shows significant performance impairment, as measured by the continuous performance test and the span of apprehension, not only in schizophrenic patients but in some populations at high risk for schizophrenia. Studies of backward masking suggest that the time taken to transfer a stimulus from the stage of registration to short-term memory may be slowed in schizophrenia, although other interpretations are possible. Skin resistance orienting responses are absent in about 50 percent of adult schizophrenics, and there is some evidence that this absence may reflect a trait. Studies should now test the trait status of all these psychophysiological variables and probe into the significance of the measures used. In these efforts, both the testing of first degree family members and the standardization of testing techniques are recommended.