- Email: [email protected]
Correlation between prostaglandin release from cerebral cortex and electrocorticogram in unanesthetized cats
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
FREE COMMUNICATIONS IN EEG further with electrical stimulation of the reticular formation at levels which induced electrocortical arousal. A d m i n i s t r a t i o n of chlorpromazine (1.0-8.0 mg/kg) not only depressed the spontaneous release of prostaglandins, but blocked the increase evoked by stimulation, concomitantly with blocking electrocortical arousal. Increasing the stimulating voltage to restore the arousal response also restored the evoked release of prostaglandins. Most of the prostaglandin-like material released spontaneously was represented by 'E' type compounds, whereas the increase with stimulation was mainly of the ' F ' compounds. It is thought that, whilst the prostaglandins are unlikely to be synaptic transmitters in the central nervous system, they must have some function connected with neuronal mechanisms.
115. The EEG in acute barbiturate intoxication, with particular reference to isoeleetric EEGs. - S . Sament and A. D. Huott (Boston, Mass., U.S.A.). The EEGs in 26 cases of acute barbiturate intoxication have been classified as follows: Stage I Normal EEG with small amplitude fast activity (1 case) Stage II Predominantly alpha with some theta activity (9 cases) Stage III Predominantly theta activity (5 cases) Stage IV Predominantly delta activity (3 cases) Stage V Isoelectric with bursts of sharp activity (2 cases) Stage VI Completely isoelectric (6 cases) Stages I-III were associated with drowsiness or confusion. Stages IV-VI were associated with coma, and these three stages could not be distinguished clinically, or by barbiturate levels. In Stage IV, all patients survived. In Stage V, one patient survived. In Stage VI, all patients died. Causes of death were cardio-respiratory failure and anoxia, pneumonia, and renal failure. If these complications can be prevented, all cases of barbiturate intoxication are potentially reversible. The blood barbiturate correlated poorly with the state of consciousness, or the EEG. Other investigators have shown that the EEG is the best single measure of the depth of barbiturate narcosis and that it was superior, in this respect, to clinical or biochemical testing: these studies were performed experimentally on cats and also during thiopentone anesthesia in man. The present study shows the same conclusions for barbiturate intoxication in man. There is a direct correlation between the EEG changes, described above, and the complications that might be anticipated. T h u s cardiac
695
arrest has occurred only during Stage VI, whereas respiratory failure occurred during Stage III-VI. The present study also shows that depression of tendon jerks, absent pupillary and corneal reflexes, and immobility of the eyes do not, in themselves, indicate a poor prognosis.
116. Rhythmic afterwaves to flashes in relation to amplitude and phase of foregoing and subsequent alpha activity.-J. S. Barlow and R. W. Lansing (Boston, Mass., U.S.A.). Although a number of aspects have been previously described concerning the relationship between intrinsic or background alpha activity and the rhythmic waves of alpha frequency which are induced b y slowly repeated flashes, the exact nature of their interaction has remained unclear. In the present study, we have explored this question further in a series of recordings of EEGs from normal subjects presented with slowly repeated flashes at randomized intervals. Amplitude of background alpha was obtained by full-wave rectification and smoothing (i.e., envelope detection) of the 7-14 c/sec filtered EEG. Averages of both the envelope (i.e., of alpha spindles) and the raw EEG were computed with respect both to the stimuli and with respect to the phase of the foregoing (as well as the subsequent) background alpha activity. Averages were further approportioned according to the instantaneous amplitude of the immediately foregoing alpha activity, by means of an electronic kick-sorter operated in conjunction with a level detector whose input was the alpha envelope. Preliminary results from the study suggest the following: (1) The average amplitude of rhythmic afterwaves is not dependent on the amplitude of the immediately foregoing alpha activity. (2) In contrast, the trend of amplitude of the envelope of the EEG following each stimulus, is dependent on the amplitude of the immediately foregoing alpha rhythm, such that larger amplitudes tend to diminish, and smaller amplitudes to increase, on the average, immediately following a flash, waves of a foregoing alpha spindle, irrespective of their amplitude, can remain in phase with themselves for a relatively long period (e.g., through two successive flash-intervals). (4) In contrast, flashinduced rhythmic afterwaves tend to be disrupted, or reset in phase, by successive flashes. (5) Alpha waves that reappear following alpha-blocking to flash are largely independent, with respect to phase, of the foregoing alpha activity, i.e., the alpha rhythm does not reappear "in phase" with itself. These findings will be discussed in relation to the general problem of the origin of alpha activity.
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
FREE COMMUNICATIONS IN EEG further with electrical stimulation of the reticular formation at levels which induced electrocortical arousal. A d m i n i s t r a t i o n of chlorpromazine (1.0-8.0 mg/kg) not only depressed the spontaneous release of prostaglandins, but blocked the increase evoked by stimulation, concomitantly with blocking electrocortical arousal. Increasing the stimulating voltage to restore the arousal response also restored the evoked release of prostaglandins. Most of the prostaglandin-like material released spontaneously was represented by 'E' type compounds, whereas the increase with stimulation was mainly of the ' F ' compounds. It is thought that, whilst the prostaglandins are unlikely to be synaptic transmitters in the central nervous system, they must have some function connected with neuronal mechanisms.
115. The EEG in acute barbiturate intoxication, with particular reference to isoeleetric EEGs. - S . Sament and A. D. Huott (Boston, Mass., U.S.A.). The EEGs in 26 cases of acute barbiturate intoxication have been classified as follows: Stage I Normal EEG with small amplitude fast activity (1 case) Stage II Predominantly alpha with some theta activity (9 cases) Stage III Predominantly theta activity (5 cases) Stage IV Predominantly delta activity (3 cases) Stage V Isoelectric with bursts of sharp activity (2 cases) Stage VI Completely isoelectric (6 cases) Stages I-III were associated with drowsiness or confusion. Stages IV-VI were associated with coma, and these three stages could not be distinguished clinically, or by barbiturate levels. In Stage IV, all patients survived. In Stage V, one patient survived. In Stage VI, all patients died. Causes of death were cardio-respiratory failure and anoxia, pneumonia, and renal failure. If these complications can be prevented, all cases of barbiturate intoxication are potentially reversible. The blood barbiturate correlated poorly with the state of consciousness, or the EEG. Other investigators have shown that the EEG is the best single measure of the depth of barbiturate narcosis and that it was superior, in this respect, to clinical or biochemical testing: these studies were performed experimentally on cats and also during thiopentone anesthesia in man. The present study shows the same conclusions for barbiturate intoxication in man. There is a direct correlation between the EEG changes, described above, and the complications that might be anticipated. T h u s cardiac
695
arrest has occurred only during Stage VI, whereas respiratory failure occurred during Stage III-VI. The present study also shows that depression of tendon jerks, absent pupillary and corneal reflexes, and immobility of the eyes do not, in themselves, indicate a poor prognosis.
116. Rhythmic afterwaves to flashes in relation to amplitude and phase of foregoing and subsequent alpha activity.-J. S. Barlow and R. W. Lansing (Boston, Mass., U.S.A.). Although a number of aspects have been previously described concerning the relationship between intrinsic or background alpha activity and the rhythmic waves of alpha frequency which are induced b y slowly repeated flashes, the exact nature of their interaction has remained unclear. In the present study, we have explored this question further in a series of recordings of EEGs from normal subjects presented with slowly repeated flashes at randomized intervals. Amplitude of background alpha was obtained by full-wave rectification and smoothing (i.e., envelope detection) of the 7-14 c/sec filtered EEG. Averages of both the envelope (i.e., of alpha spindles) and the raw EEG were computed with respect both to the stimuli and with respect to the phase of the foregoing (as well as the subsequent) background alpha activity. Averages were further approportioned according to the instantaneous amplitude of the immediately foregoing alpha activity, by means of an electronic kick-sorter operated in conjunction with a level detector whose input was the alpha envelope. Preliminary results from the study suggest the following: (1) The average amplitude of rhythmic afterwaves is not dependent on the amplitude of the immediately foregoing alpha activity. (2) In contrast, the trend of amplitude of the envelope of the EEG following each stimulus, is dependent on the amplitude of the immediately foregoing alpha rhythm, such that larger amplitudes tend to diminish, and smaller amplitudes to increase, on the average, immediately following a flash, waves of a foregoing alpha spindle, irrespective of their amplitude, can remain in phase with themselves for a relatively long period (e.g., through two successive flash-intervals). (4) In contrast, flashinduced rhythmic afterwaves tend to be disrupted, or reset in phase, by successive flashes. (5) Alpha waves that reappear following alpha-blocking to flash are largely independent, with respect to phase, of the foregoing alpha activity, i.e., the alpha rhythm does not reappear "in phase" with itself. These findings will be discussed in relation to the general problem of the origin of alpha activity.