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EOG artifact removal from EEG ERP topographic maps
28A
BIOL PSYCHIATRY 1989;25:21A-33A
Neurophysiological Studies
only 0.32. We conclude that automatic reject methods are not effective solutions to the problem.
57
EOG ARTIFACT REMOVAL FROM EEG ERP TOPOGRAPHIC MAPS S.F. Sands, S.F. Faux, R.W. McCarley El Paso, TX and Brockton,
MA
Eye blinks and movements (EOG) can seriously contaminate topographic maps of EEG and event-related potentials (ERP) especially in psychiatric populations. We have thus employed an offline regression-based algorithm (Semlitsch et al., 1986) to remove EOG signals while leaving brain electrical topography intact. To determine the validity of corrected-EEG (c-EEG) in our patient studies, we performed two studies which compared c-EEG versus artifact-free EEG (af-EEG). The first study showed that the spectral rms voltage (delta band) of c-EEG (5.8 pV) from ten normal subjects in frontal leads was significantly smaller (p < .05) than that of af-EEG with artifacts removed by visual editing (9.6 pV) or computer rejection (9.5 pV using + 50 p,V window) EEG. In a second study, auditory and visual ERPs were recorded from 12 normal subjects using a visual and an auditory oddball target discrimination. Subjects detected rare targets under a blinking (B) and an eye-fixated (F) condition. Eyeblink corrected grand averaged ERPs (B-ERP) and F grand-averaged ERPs (F-ERP) had high intraclass correlations (Rhoi = .92 - .97). There were no significant differences between B- and F-ERP P3 amplitudes integrated over 300-400 milliseconds at any lo-20 site (p > .90, paired t-values (lldf) between 0.0 - 0.4).
58
CLINICAL CORRELATES OF NONRESPONSIVENESS OF THE AUTONOMIC ORIENTING RESPONSE IN PATIENTS WITH SCHIZOPHRENIA David B. Schnur, Alvin S. Bernstein, Sukdeb Mukherjee, James Reidel, Barry Dunayer New York. NY A well replicated finding in schizophrenia research is that about 50% of patients fail to show an autonomic orienting response (OR) to innocuous stimuli. Studies of clinical correlates of OR response status have yielded disparate findings, although a relation between OR nonresponsiveness and reduced levels of excitement have been reported by several investigators. To examine further relations between clinical symptoms and OR response status, we assessed patients meeting RDC for schizophrenic disorder using the Schedule for Affective Disorders and Schizophrenia, the Brief Psychiatric Rating Scale, the Scale for the Assessment of Negative Symptoms, and the Negative Symptom Rating Scale. Skin conductance and finger pulse volume OR were measured within three days of the clinical assessment. Preliminary findings from 19 patients indicate that nine were OR nonresponders defined on the basis of a failure to respond to both autonomic OR components. OR response status was not related to age, duration of illness, medication status, negative symptoms, or global severity of illness. However, the hallucinations (p = .OOl) and delusions (p = .012) were significantly more severe in OR nonresponders than in OR responders. These productive psychotic symp-
BIOL PSYCHIATRY 1989;25:21A-33A
Neurophysiological Studies
only 0.32. We conclude that automatic reject methods are not effective solutions to the problem.
57
EOG ARTIFACT REMOVAL FROM EEG ERP TOPOGRAPHIC MAPS S.F. Sands, S.F. Faux, R.W. McCarley El Paso, TX and Brockton,
MA
Eye blinks and movements (EOG) can seriously contaminate topographic maps of EEG and event-related potentials (ERP) especially in psychiatric populations. We have thus employed an offline regression-based algorithm (Semlitsch et al., 1986) to remove EOG signals while leaving brain electrical topography intact. To determine the validity of corrected-EEG (c-EEG) in our patient studies, we performed two studies which compared c-EEG versus artifact-free EEG (af-EEG). The first study showed that the spectral rms voltage (delta band) of c-EEG (5.8 pV) from ten normal subjects in frontal leads was significantly smaller (p < .05) than that of af-EEG with artifacts removed by visual editing (9.6 pV) or computer rejection (9.5 pV using + 50 p,V window) EEG. In a second study, auditory and visual ERPs were recorded from 12 normal subjects using a visual and an auditory oddball target discrimination. Subjects detected rare targets under a blinking (B) and an eye-fixated (F) condition. Eyeblink corrected grand averaged ERPs (B-ERP) and F grand-averaged ERPs (F-ERP) had high intraclass correlations (Rhoi = .92 - .97). There were no significant differences between B- and F-ERP P3 amplitudes integrated over 300-400 milliseconds at any lo-20 site (p > .90, paired t-values (lldf) between 0.0 - 0.4).
58
CLINICAL CORRELATES OF NONRESPONSIVENESS OF THE AUTONOMIC ORIENTING RESPONSE IN PATIENTS WITH SCHIZOPHRENIA David B. Schnur, Alvin S. Bernstein, Sukdeb Mukherjee, James Reidel, Barry Dunayer New York. NY A well replicated finding in schizophrenia research is that about 50% of patients fail to show an autonomic orienting response (OR) to innocuous stimuli. Studies of clinical correlates of OR response status have yielded disparate findings, although a relation between OR nonresponsiveness and reduced levels of excitement have been reported by several investigators. To examine further relations between clinical symptoms and OR response status, we assessed patients meeting RDC for schizophrenic disorder using the Schedule for Affective Disorders and Schizophrenia, the Brief Psychiatric Rating Scale, the Scale for the Assessment of Negative Symptoms, and the Negative Symptom Rating Scale. Skin conductance and finger pulse volume OR were measured within three days of the clinical assessment. Preliminary findings from 19 patients indicate that nine were OR nonresponders defined on the basis of a failure to respond to both autonomic OR components. OR response status was not related to age, duration of illness, medication status, negative symptoms, or global severity of illness. However, the hallucinations (p = .OOl) and delusions (p = .012) were significantly more severe in OR nonresponders than in OR responders. These productive psychotic symp-