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A single-sweep analysis of visually evoked P300 waves in healthy subjects and schizophrenics
46P
Society proceedings
1 year. One leg muscle and one arm muscle were examined every 3 months. Three patients showed predominantly bulbar symptoms and a distinct, comparably smaller increase of amplitudes and areas as well as a small decrease of the number of motor units. In 3 other patients those parameters showed more changes. In two patients with rapid clinical progression, a small decrease in amplitudes and a surprisingly high increase of areas was observed that could be interpreted as a desynchronization of terminal axonal motoric fibers. Field potentials after stimulation also revealed a distinct loss of motor units with reduction of amplitude and increase of area. These methods can be used as prognostic indicators in a short time of observation.
33.
Loudness dependence of auditory-evoked N1/P2-component as predictor of clinical response to serotonin agonists in patients with affective disorders - U. Hegerl, J. Gallinat, T. Bauch, A. Munke, R. Bottlender, H.-J. M~iller (Psychiatrische Klinik der Ludwig-Maximilians-Universitiit, Miinchen)
Both preclinical and clinical studies indicate that the dependence of the auditory evoked potentials (AEP) on stimulus loudness is negatively related to central serotonergic neurotransmission and may be useful as a predictor of clinical response to serotonin agonists. The hypothesis is tested that a pronounced loudness dependence of the AEP, which reflects low serotonergic functioning, is related to a favorable clinical response to serotonin agonists in patients with affective disorders. SSRI responders (50% decrease in Hamilton Depression Score after 4 weeks) and responders to preventive lithium treatment (no recurrence with hospitalization during lithium medication in the last 4 years) were compared to the corresponding non-responders. AEP to stimuli with different intensities were recorded (32 channels). Using dipole source analysis, we calculated the loudness dependence of the tangential Nl/P2-dipole activity. Both the responders to preventive lithium treatment as well as depressed patients responding to SSRI were characterized by a significantly stronger loudness dependence. The loudness dependence of the AEP can give clinically relevant information concerning the individual patient's response probability to serotonin agonists.
34.
Ocuiographic findings after frontal eye field lesions. - W. Heide, D. Kiimpf (Dept. of Neurology, Medical University, D23538 Liibeck)
To evaluate the specific role of the human frontal eye field (FEF), we investigated eye movement disorders after selective FEF lesions. Subjects were 3 patients with postischemic lesions in the right precentral sulcus and gyrus, the hypothesized FEF location. Horizontal saccadic and smooth pursuit responses to predictably and unpredictably moving visual targets were recorded using infrared reflection oculography. Thirty healthy adults and two patients with lesions of the right prefrontal cortex served as controls. In FEF patients, visually-guided saccades did not differ from normals, but antisaccades and memoryguided saccades had prolonged latencies and highly elevated error rates of inappropriate reflexive saccades to the target. Particularly during systematic exploration of an abstract visual display, FEF patients performed fewer exploratory saccades than controls and neglected the eontralateral hemifield. With predictive target motion more than with unpredictable stimuli, rightward (ipsiversive) smooth pursuit was saccadie and of low velocity. In patients with prefrontal lesions, these functions were mostly normal. FEF lesions specifically impair the velocity of ipsiversive smooth pursuit, the initiation of voluntary saccades and the voluntary suppression of inappropriate, visually-triggered reflexive saccades. In addition, systematic voluntary saccadic exploration is reduced more in the contralesional hemifield, which reflects frontal exploratory-motor neglect.
35.
A single-sweep analysis of visually evoked P300 waves in healthy subjects and schizophrenics. - (;. Heinz, M. Rubly, ,|.
Fuhrmeister (Universitiits-Nervenklinik, Psychiatrie und Psychotherapie, D-66421 Homburg) Schizophrenics usually show smaller P300 waves than healthy subjects. It is uncertain whether this results from smaller P300 waves after single target stimuli or whether schizophrenics generate fewer P300 waves after target stimuli. To examine this, we elicited P300 waves in 10 healthy subjects and 17 schizophrenics in competitive visual stimulation with a checkerboard reversal pattern, using a correlation procedure to analyse single sweeps. We used two different patterns as reference: (i) a 'normal potential' derived from the healthy subjects and (ii) the individual ERP as an individual reference. As a result we found that both healthy subjects and schizophrenics generate a wide variation of ERP responses subsequent to target stimuli and to non-target stimuli. Schizophrenics generate fewer ERPs after target stimuli (N-ref.: 40% vs. 60%) but more after non-target stimuli (N-ref.: 30% vs. 20%) in comparison to healthy subjects. This results in smaller P300 waves after target stimuli than in healthy subjects, but in larger P300 waves subsequent to non-target stimuli relative to healthy subjects. Thus, the single-sweep analysis demonstrates an overlap of the processing of target and non-target stimuli in schizophrenics. This suggests a decreased ability of schizophrenics to maintain a focus of attention, resulting in a decreased ability to differentiate between relevant and irrelevant stimuli.
36.
A correlation procedure for the single-sweep analysis of eventrelated potentials. - G. Heinz, M. Rubly, J. Fuhrmeister (Universit~its-Nervenklinik, Psychiatric und Psychotherapie, D-66421 Homburg)
Event-related potentials are calculated by averaging a certain number of stimulus-related EEG-sections. However, the assumption that every target stimulus results in a more or less equal potential, is usually not tested. Our investigation deals with this question and checks whether only target stimuli, and no non-target stimuli, elicit eventrelated potentials. The method involved correlating single-sweep EEGsections with a reference-pattern. Two different reference-patterns were used: (i) a 'normal potential' derived from healthy subjects and (ii) the individual ERP as an individual reference. The ERPs were elicited by a checkerboard-reversal-pattern with two different relations of target and non-target frequencies (competitive stimulation). Correlations with both of the reference-potentials revealed a large variation of endogenous potentials elicited by target stimuli (N-ref. 16-88%, l-ref. 4 0 94%) and by non-target stimuli (N-ref. 1-56%, l-ref. 4-48%). A greater number of typical 'target potentials' was recorded after target stimuli and a smaller number of 'target potentials' after non-target stimuli. Alter averaging, this resulted in large P3(/0 waves subsequent to target stimuli and small P300 waves in non-target stimuli. Furthermore, the two references led to quite different results, depending on the degree to which the individual's ERP deviated from 'normal' potential. The practical significance of this method can be shown in a comparative examination of healthy subjects with schizophrenic patients. 37.
Evoked muscular responses ('long loop reflex') as electrophysiologic method of monitoring the course of the disease and treatment in multiple sclerosis patients. - A. Helminiak, R. Podemski (Neurological Department, Medical University of Wroclaw, ul. Traugutta 118, Wroclaw, Poland)
Late muscle responses, evoked by an electric stimulation of peripheral nerve, are based on a long, polysynaptic reflex arc which includes aflet'ent and efl'erent structures of spinal cord, brainstem and hemispheres ('long loop'). In 15 patients with MS (mean age 33.6 years), responses from abductor pollicis brevis, evoked by stimulating the median nerve with square wave impulse, were assessed during a relapse of the disease. Latency and amplitude of R 1 and R2 responses (spinal and 'long loop reflex', respectively) we.re analyzed. The examination
Society proceedings
1 year. One leg muscle and one arm muscle were examined every 3 months. Three patients showed predominantly bulbar symptoms and a distinct, comparably smaller increase of amplitudes and areas as well as a small decrease of the number of motor units. In 3 other patients those parameters showed more changes. In two patients with rapid clinical progression, a small decrease in amplitudes and a surprisingly high increase of areas was observed that could be interpreted as a desynchronization of terminal axonal motoric fibers. Field potentials after stimulation also revealed a distinct loss of motor units with reduction of amplitude and increase of area. These methods can be used as prognostic indicators in a short time of observation.
33.
Loudness dependence of auditory-evoked N1/P2-component as predictor of clinical response to serotonin agonists in patients with affective disorders - U. Hegerl, J. Gallinat, T. Bauch, A. Munke, R. Bottlender, H.-J. M~iller (Psychiatrische Klinik der Ludwig-Maximilians-Universitiit, Miinchen)
Both preclinical and clinical studies indicate that the dependence of the auditory evoked potentials (AEP) on stimulus loudness is negatively related to central serotonergic neurotransmission and may be useful as a predictor of clinical response to serotonin agonists. The hypothesis is tested that a pronounced loudness dependence of the AEP, which reflects low serotonergic functioning, is related to a favorable clinical response to serotonin agonists in patients with affective disorders. SSRI responders (50% decrease in Hamilton Depression Score after 4 weeks) and responders to preventive lithium treatment (no recurrence with hospitalization during lithium medication in the last 4 years) were compared to the corresponding non-responders. AEP to stimuli with different intensities were recorded (32 channels). Using dipole source analysis, we calculated the loudness dependence of the tangential Nl/P2-dipole activity. Both the responders to preventive lithium treatment as well as depressed patients responding to SSRI were characterized by a significantly stronger loudness dependence. The loudness dependence of the AEP can give clinically relevant information concerning the individual patient's response probability to serotonin agonists.
34.
Ocuiographic findings after frontal eye field lesions. - W. Heide, D. Kiimpf (Dept. of Neurology, Medical University, D23538 Liibeck)
To evaluate the specific role of the human frontal eye field (FEF), we investigated eye movement disorders after selective FEF lesions. Subjects were 3 patients with postischemic lesions in the right precentral sulcus and gyrus, the hypothesized FEF location. Horizontal saccadic and smooth pursuit responses to predictably and unpredictably moving visual targets were recorded using infrared reflection oculography. Thirty healthy adults and two patients with lesions of the right prefrontal cortex served as controls. In FEF patients, visually-guided saccades did not differ from normals, but antisaccades and memoryguided saccades had prolonged latencies and highly elevated error rates of inappropriate reflexive saccades to the target. Particularly during systematic exploration of an abstract visual display, FEF patients performed fewer exploratory saccades than controls and neglected the eontralateral hemifield. With predictive target motion more than with unpredictable stimuli, rightward (ipsiversive) smooth pursuit was saccadie and of low velocity. In patients with prefrontal lesions, these functions were mostly normal. FEF lesions specifically impair the velocity of ipsiversive smooth pursuit, the initiation of voluntary saccades and the voluntary suppression of inappropriate, visually-triggered reflexive saccades. In addition, systematic voluntary saccadic exploration is reduced more in the contralesional hemifield, which reflects frontal exploratory-motor neglect.
35.
A single-sweep analysis of visually evoked P300 waves in healthy subjects and schizophrenics. - (;. Heinz, M. Rubly, ,|.
Fuhrmeister (Universitiits-Nervenklinik, Psychiatrie und Psychotherapie, D-66421 Homburg) Schizophrenics usually show smaller P300 waves than healthy subjects. It is uncertain whether this results from smaller P300 waves after single target stimuli or whether schizophrenics generate fewer P300 waves after target stimuli. To examine this, we elicited P300 waves in 10 healthy subjects and 17 schizophrenics in competitive visual stimulation with a checkerboard reversal pattern, using a correlation procedure to analyse single sweeps. We used two different patterns as reference: (i) a 'normal potential' derived from the healthy subjects and (ii) the individual ERP as an individual reference. As a result we found that both healthy subjects and schizophrenics generate a wide variation of ERP responses subsequent to target stimuli and to non-target stimuli. Schizophrenics generate fewer ERPs after target stimuli (N-ref.: 40% vs. 60%) but more after non-target stimuli (N-ref.: 30% vs. 20%) in comparison to healthy subjects. This results in smaller P300 waves after target stimuli than in healthy subjects, but in larger P300 waves subsequent to non-target stimuli relative to healthy subjects. Thus, the single-sweep analysis demonstrates an overlap of the processing of target and non-target stimuli in schizophrenics. This suggests a decreased ability of schizophrenics to maintain a focus of attention, resulting in a decreased ability to differentiate between relevant and irrelevant stimuli.
36.
A correlation procedure for the single-sweep analysis of eventrelated potentials. - G. Heinz, M. Rubly, J. Fuhrmeister (Universit~its-Nervenklinik, Psychiatric und Psychotherapie, D-66421 Homburg)
Event-related potentials are calculated by averaging a certain number of stimulus-related EEG-sections. However, the assumption that every target stimulus results in a more or less equal potential, is usually not tested. Our investigation deals with this question and checks whether only target stimuli, and no non-target stimuli, elicit eventrelated potentials. The method involved correlating single-sweep EEGsections with a reference-pattern. Two different reference-patterns were used: (i) a 'normal potential' derived from healthy subjects and (ii) the individual ERP as an individual reference. The ERPs were elicited by a checkerboard-reversal-pattern with two different relations of target and non-target frequencies (competitive stimulation). Correlations with both of the reference-potentials revealed a large variation of endogenous potentials elicited by target stimuli (N-ref. 16-88%, l-ref. 4 0 94%) and by non-target stimuli (N-ref. 1-56%, l-ref. 4-48%). A greater number of typical 'target potentials' was recorded after target stimuli and a smaller number of 'target potentials' after non-target stimuli. Alter averaging, this resulted in large P3(/0 waves subsequent to target stimuli and small P300 waves in non-target stimuli. Furthermore, the two references led to quite different results, depending on the degree to which the individual's ERP deviated from 'normal' potential. The practical significance of this method can be shown in a comparative examination of healthy subjects with schizophrenic patients. 37.
Evoked muscular responses ('long loop reflex') as electrophysiologic method of monitoring the course of the disease and treatment in multiple sclerosis patients. - A. Helminiak, R. Podemski (Neurological Department, Medical University of Wroclaw, ul. Traugutta 118, Wroclaw, Poland)
Late muscle responses, evoked by an electric stimulation of peripheral nerve, are based on a long, polysynaptic reflex arc which includes aflet'ent and efl'erent structures of spinal cord, brainstem and hemispheres ('long loop'). In 15 patients with MS (mean age 33.6 years), responses from abductor pollicis brevis, evoked by stimulating the median nerve with square wave impulse, were assessed during a relapse of the disease. Latency and amplitude of R 1 and R2 responses (spinal and 'long loop reflex', respectively) we.re analyzed. The examination