Topographic Differences between Normals and Schizophrenics: The N120 Evoked Potential Component

217

100

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.

Section: Event-related Potentialsmentioning

confidence: 88%

Recent Studies of Psychophysiology in Schizophrenia

Holzman

1987

217

100

“…The defect was not observed with the visual EP using similar paradigms (Adler et al 1985). Using backward masking, Patterson et al (1986) suggest EP deficits in schizophrenic subjects at intervals < 100 ms. Reports of abnormalities in EP responses of schizophrenics continue to appear regularly (e.g., Morstyn et al 1983; Steinhauer 1985; Buchsbaum et al 1986). The results are exciting because they offer the potential of matching sensory deficits to neurophysiological substrates through topographical mapping of the EPs.…”

Section: Information-processing Studies In Schizophreniamentioning

confidence: 99%

Elevated Thalamic Dopamine: Possible Link to Sensory Dysfunctions in Schizophrenia

Oke¹,

Adams²

1987

115

Sensory-processing dysfunctions, deficit states, and the combinations of seemingly disparate behavioral symptoms of schizophrenia are addressed with regard to a common thread--the possibility of dysfunctional processing in the thalamus. Recent views of the connectional neuroanatomy and electrical activity of thalamus are examined. A hypothesis is presented in which disturbances in the timing and phasic neuronal activity of the thalamus and, especially, its connections with other brain regions may result in many of the behavioral manifestations of schizophrenia. It is suggested that neurotransmitter or other chemical imbalances might produce such thalamic disturbances. Experimental findings of enhanced dopamine content in the thalami of schizophrenic patients are reported. Several varieties of distributional patterns of this elevated dopamine are shown and evaluated.

“…Initial topographic maps of selective attention enhancement of evoked potential amplitude showed a temporoparietal, rather than frontal, difference between normals and schizophrenics, however (Buchsbaum et al 1982c). A somatosensory stimulus produced topographic differences in somatosensory cortex (Buchsbaum et al 1986a), suggesting the importance of stimulus modality and task for locale of EP differences.…”

Section: Computer Electroencephalographic Topography (Cet)mentioning

confidence: 99%

Functional and Anatomical Brain Imaging: Impact on Schizophrenia Research

Buchsbaum

Haier

1987

A group of related new technologies has made it possible to study the brain's regional changes in metabolism, blood flow, electrical activity, and neurochemistry. Positron emission tomography (PET) produces slice images of radioisotope density--brain metabolism or receptor concentration can be quantitated. Studies in schizophrenia have indicated relative metabolic underactivity of the frontal lobes of schizophrenics. Decreased activity in the basal ganglia, which can be reversed with neuroleptic treatment, is also seen in schizophrenia. PET studies are in the early stages; standard methodology for isotope selection, task during tracer uptake, and quantitative analysis is still developing. Cerebral blood flow studies have shown similar patterns in the cortical surface. The electroencephalogram provides a short time resolution approach which can assess attention and arousal, but lacks some of the anatomic exactness and depth capabilities of PET. Magnetic resonance imaging furnishes anatomical images of gray and white matter previously unavailable with x-ray computed tomography. Advances in methodology and clinical studies with imaging are making neuroanatomic theories of schizophrenia more directly testable than ever before.