This paper reviews the literature on the Nl wave of the human auditory evoked potential. It concludes that at least six different cerebral processes can contribute to (he negative wave recorded from the scalp with a peak latency between 50 and 150 ms: a component generated in the auditory-cortex on the supratemporal plane, a component generated in the association cortex on the lateral aspect of the temporal and parietal cortex, a component generated in the motor and premotor cortices, the mismatch negativity, a temporal component of the processing negativity, and a frontal component of the processing negativity, The first three, which can be considered ‘true’ N1 components, are controlled by the physical and temporal aspects of the stimulus and by the general state of the subject. The other three components are not necessarily elicited by a stimulus but depend on the conditions in which the stimulus occurs. They often last much longer than the true N1 components that they overlap.

The N1 wave of the human electric and magnetic response to sound: a review and an analysis of the component structure

The effects of two kinds of experimental manipulation of semantic meaning were studied in Evoked Potentials (EPs), brain responses recorded from scalp monitors. Both kinds of semantic manipulation were based on Osgood's rating analyses which described three primary dimensions of connotative meaning: Evaluation, Potency, and Activity (E, P, and A). One kind of experimental variable was the semantic class of the stimulus word (E+, E-, P+, P-, A+, A-). The other kind of experimental variable was the semantic dimension of the rating scale (E, P, A) which the subject used to make semantic judgments ab out the stimulus words. These variables were experimentally combined in that for each trial the subject used adesignated semantic scale to judge a specified stimulus word while brain activity was recorded. Using multivariate procedures, both stimulus word class and scale dimension effects on the EPs were found. Individual subject analyses demonstrated the generality of the results by showing successful discrimination of word classes and scale dimensions for each of the ten subjects analyzed separately. Supported in part by NIH Research Grant 5 R01 EY01593 and the Advanced Research Projects Agency (Contract N00014-77-C-0037). The author thanks John W. McCrary and John A. Chapman for their collaboration in this research and Janice K. Martin for her assistance.

Evoked Brain Potentials and Behavior

The role of a reduced N100 (or N1) component of the auditory event related potential as a potential trait marker of schizophrenia is critically discussed in this review. We suggest that the extent of the N100 amplitude reduction in schizophrenia depends on experimental and subject factors, as well as on clinical variables: N100 is more consistently reduced in studies using interstimulus intervals (ISIs) > 1 s than in studies using shorter ISIs. An increase of the N100 amplitude by allocation of attention is often lacking in schizophrenia patients. A reduction of the N100 amplitude is nevertheless also observed when such an allocation is not required, proposing that both endogenous and exogenous constituents of the N100 are affected by schizophrenia. N100 is more consistently reduced in medicated than unmedicated patients, but a reduction of the N100 amplitude as a consequence of antipsychotic medication was shown in only two of seven studies. In line with that, the association between the N100 reduction and degree of psychopathology of patients appears to be weak overall. A reduced N100 amplitude is found in first degree relatives of schizophrenia patients, but the risk of developing schizophrenia is not reflected in the N100 amplitude reduction.

Reduced auditory evoked potential component N100 in schizophrenia — A critical review

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.

/pdf/recent-studies-of-psychophysiology-in-schizophrenia-4xak4t5911.pdf

Recent Studies of Psychophysiology in Schizophrenia

Evoked potential indices of an early and late stage of attentional processing were recorded from schizophrenic and normal subjects during dichotic listening tasks. Despite slow and inaccurate detections, the schizophrenic subjects were able to focus selectively to different ears but only at a fast stimulation rate, showing integrity of the early selective stage. They showed an abnormal late stage, indicating inefficiency in processing information from detected targets. Marked deficits at a slow stimulation rate and during divided attention suggest that the schizophrenic attention disorder is one of control and maintenance of a selective processing strategy rather than of general slowness or absence of selectivity.

Schizophrenia: a neurophysiological evaluation of abnormal information processing

The authors investigated the clinical symptomatology, auditory evoked responses, and quantitatively analyzed EEGs of chronic schizophrenic patients with thought process disorder (TPD), schizophrenic patients without TPD, and matched normal volunteers. They describe the differences they found in terms of the variability, shape, latency, and amplitude of the patterns of the evoked potentials for the three groups. They also attempt to relate the neurophysiological findings with some characteristics of thought process disorder.

Auditory evoked response, EEG, and thought process in schizophrenics.

Changes in Somatosensory Evoked Potentials during Fluphenazine Treatment

methylphenidate, dextroamphetamine somatosensory evoked potential

Effect of Stimulatory Drugs on the Somatosensory Evoked Potential in Man

Somatosensory, visual and auditory evoked responses were studied in a left hemispherectomized patient. Median nerve stimulation and light flashes produced typical answers over only the unoperated hemi

Evoked Responses After Hemispherectomy

Thiothixene in childhood psychoses.

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