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Frequency analysis of the EEG under different behavioral states
694
INTERNATIONAL FEDERATION - 7TH CONGRESS
tion of the third central m o m e n t (which determines the skewness of the amplitude distribution). As skewness may arise either from interrelations between frequency components (due to nonlinearities) or from non-stationarity, the bispectrum may display important additional information about the properties of a stochastic signal such as the EEG. Obviously this information may prove to be of great value in the investigation of harmonic relationships between different frequency bands, e.g., between 0t and /3 activity, or between ct activity and slow posterior rhythms. In addition some new insights into the non-linear aspects of the EEG generating process might be expected. Because of the lengthy calculations, the computation of a bispectrum is a tedious and very time consuming task and until today only a few bispectra of geophysical data have been calculated. The introduction of the Fast Fourier Transform and our previous experience with this alogrithm in EEG analysis form the basis of a program which computes the bispectrum of an EEG sample within reasonable time. Bispectra of artificial signals will be shown in order to explain the basic aspects of the extension of conventional spectrum analysis, and selected examples of bispectra of actual EEG data will demonstrate the interesting possibilities which this method offers for EEG analysis. 112. EEG changes during arch aortography.-S.
Satran, E. O. Lipchik, C. O. Barley and K. Coast (Rochester, N.Y., U.S.A.). EEG studies were performed on 19 patients (mean age 66 years) during four vessel arch aortography. All patients had signs and symptoms of occlusive vascular disease. In 10 patients X-ray studies revealed surgically significant extracranial stenoses of the internal carotid arteries. During angiography no changes w e r e noted in the overall background activity of the EEG. Minor EEG abnormalities in the pre-angiographic records were not more manifest during or after arteriography. No untoward responses were noted during the angiographic procedures. Eight patients had carotid endarterectomy and follow-up EEGs 3-4 days after surgery. Six patients had accentuation of minor weight EEG abnormalities present before surgery. The most frequent change was the occurrence of high voltage polyrhythmic mid-temporal delta activity. Arch aortography performed for the diagnosis of occlusive cerebrovascular disease is a procedure of low risk which does not alter the EEG.
113. Frequency analysis of the EEG under dif-
ferent behavioral states.-D. (Chicago, Ill., U.S.A.).
Giannitrapani
Current methods of computer EEG analysis permit exploration of electrocortical activity changes under different behavioral states with a degree of precision not previously available. The current experiment was designed to study these changes during activities involving different kinds of auditory, visual and conceptual functions. Thirty-two right-handed males had EEGs recorded from 16 areas onto digital tape. The results of a spectral analysis in 17 frequency bands from 1 to 33 c/see were analyzed. To study auditory involvement the subject listened with eyes closed to white noise, music and verbal stimulation. Differences among the conditions, between each condition and the two control periods (awake, resting, with eyes dosed at the beginning and end of the experiment) were analyzed to determine the location and frequency component involved. To study the correlates of patterned and unpatterned vision the subject looked at a poster for the first condition and through diffusing goggles for the second. The EEG during mental arithmetic was also compared with the resting conditions. Arithmetic showed increase in fast activity (21 to 33 c/see) bilaterally, anteriorly more in prefrontal areas; for Noise, an increase in fast activity (23 to 31 c/see) in prefrontal and temporal areas bilaterally. Music simulated Noise but more weakly, with decrease at 19 c/see and increase at 33 c/see in the left occipital area. Voice simulated Noise, but in slightly higher frequency bands (27-33 c/see). Voice also showed a decrease in alpha activity in the R. post temporal and R. occipital areas, and decrease in 19 and 33 c/see in the U occipital area. The two visual conditions showed overatl changes in the prefrontal, temporal, post temporal, parietal and occipital areas, as well as selected changes in other areas. The relevance of these findings in light of current neuroanatomical knowledge is discussed.
114. Correlation between prostaglandin release from cerebral cortex and electrocorticogram in unanesthetized cats.-P. B. Bradley and G. M. R. Samuels (Birmingham, G.B.). A prostaglandin-like material has been found in superfusates of cerebral cortex in unanesthetized enc~phale isol~ cat preparations. The material was assayed on the rat uterus and identified by thin-layer chromatography. The level of spontaneous release of the prostaglandin-like material was higher than that which had been found previously in anesthetized preparations and it increased still
INTERNATIONAL FEDERATION - 7TH CONGRESS
tion of the third central m o m e n t (which determines the skewness of the amplitude distribution). As skewness may arise either from interrelations between frequency components (due to nonlinearities) or from non-stationarity, the bispectrum may display important additional information about the properties of a stochastic signal such as the EEG. Obviously this information may prove to be of great value in the investigation of harmonic relationships between different frequency bands, e.g., between 0t and /3 activity, or between ct activity and slow posterior rhythms. In addition some new insights into the non-linear aspects of the EEG generating process might be expected. Because of the lengthy calculations, the computation of a bispectrum is a tedious and very time consuming task and until today only a few bispectra of geophysical data have been calculated. The introduction of the Fast Fourier Transform and our previous experience with this alogrithm in EEG analysis form the basis of a program which computes the bispectrum of an EEG sample within reasonable time. Bispectra of artificial signals will be shown in order to explain the basic aspects of the extension of conventional spectrum analysis, and selected examples of bispectra of actual EEG data will demonstrate the interesting possibilities which this method offers for EEG analysis. 112. EEG changes during arch aortography.-S.
Satran, E. O. Lipchik, C. O. Barley and K. Coast (Rochester, N.Y., U.S.A.). EEG studies were performed on 19 patients (mean age 66 years) during four vessel arch aortography. All patients had signs and symptoms of occlusive vascular disease. In 10 patients X-ray studies revealed surgically significant extracranial stenoses of the internal carotid arteries. During angiography no changes w e r e noted in the overall background activity of the EEG. Minor EEG abnormalities in the pre-angiographic records were not more manifest during or after arteriography. No untoward responses were noted during the angiographic procedures. Eight patients had carotid endarterectomy and follow-up EEGs 3-4 days after surgery. Six patients had accentuation of minor weight EEG abnormalities present before surgery. The most frequent change was the occurrence of high voltage polyrhythmic mid-temporal delta activity. Arch aortography performed for the diagnosis of occlusive cerebrovascular disease is a procedure of low risk which does not alter the EEG.
113. Frequency analysis of the EEG under dif-
ferent behavioral states.-D. (Chicago, Ill., U.S.A.).
Giannitrapani
Current methods of computer EEG analysis permit exploration of electrocortical activity changes under different behavioral states with a degree of precision not previously available. The current experiment was designed to study these changes during activities involving different kinds of auditory, visual and conceptual functions. Thirty-two right-handed males had EEGs recorded from 16 areas onto digital tape. The results of a spectral analysis in 17 frequency bands from 1 to 33 c/see were analyzed. To study auditory involvement the subject listened with eyes closed to white noise, music and verbal stimulation. Differences among the conditions, between each condition and the two control periods (awake, resting, with eyes dosed at the beginning and end of the experiment) were analyzed to determine the location and frequency component involved. To study the correlates of patterned and unpatterned vision the subject looked at a poster for the first condition and through diffusing goggles for the second. The EEG during mental arithmetic was also compared with the resting conditions. Arithmetic showed increase in fast activity (21 to 33 c/see) bilaterally, anteriorly more in prefrontal areas; for Noise, an increase in fast activity (23 to 31 c/see) in prefrontal and temporal areas bilaterally. Music simulated Noise but more weakly, with decrease at 19 c/see and increase at 33 c/see in the left occipital area. Voice simulated Noise, but in slightly higher frequency bands (27-33 c/see). Voice also showed a decrease in alpha activity in the R. post temporal and R. occipital areas, and decrease in 19 and 33 c/see in the U occipital area. The two visual conditions showed overatl changes in the prefrontal, temporal, post temporal, parietal and occipital areas, as well as selected changes in other areas. The relevance of these findings in light of current neuroanatomical knowledge is discussed.
114. Correlation between prostaglandin release from cerebral cortex and electrocorticogram in unanesthetized cats.-P. B. Bradley and G. M. R. Samuels (Birmingham, G.B.). A prostaglandin-like material has been found in superfusates of cerebral cortex in unanesthetized enc~phale isol~ cat preparations. The material was assayed on the rat uterus and identified by thin-layer chromatography. The level of spontaneous release of the prostaglandin-like material was higher than that which had been found previously in anesthetized preparations and it increased still