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The estimation of the electrical sources of the focal spike and slow wave complex using the SSB dipole tracing method
52P
Society proceedings/Electroencephalography and clinical Neurophysiology 98 (1996) 44P-52P
mental and physical relaxation day (the R condition). After each experimental day, 8 h sleep was polygraphically recorded during the night. Sleep stages were scored according to the Rechtschaffen and Kales manual. REM sleep periodicity was estimated by the binary autocorrelation function of the non-REM-REM cycle. Whereas there were no significant differences in the average REM sleep cycle length between the 3 conditions (the average cycle length was about 90 rain), there were significant differences in REM sleep periodicity. The periodicity was the highest in the R condition and the lowest in the PS condition. These results suggest that mental and physical stress during the daytime have an effect on the timing of REM sleep at night.
45. Source localization of spike and wave complexes by use of the spline-Laplacian method. - N. Hosaka, T. Inouye, K. Shinosaki, S. Toi, Y. Matsumoto and R. Ishii (Osaka) With the spline-Laplacian method, local cortical potentials can be more accurately estimated by calculating spline-generated surface Laplaclans of EEGs over the scalp. The spline-Laplacian method permits more precise localization of epileptiform discharges because of no influence of the reference electrode. EEGs were recorded from 32 electrode locations in 4 epileptic patients with generalized asymmetric spike and slow wave complexes. The EEGs were digitized at a sampling interval of 5 msec during a 3 sec period of spike and slow wave complexes. The spline-Laplacian maps over the whole scalp were successively constructed every 5 msec. The maps were further segmented in time with cluster analysis (r-means algorithm) for the 2-dimensional Fourier transform of Laplacian estimates. Several source locations, varying greatly in position, were found at each time. Cluster analysis classified 2 different patterns of source locations for each spike and slow wave component. In each hemisphere, the spike component showed a prefrontal distribution, and the slow component a fronto-central distribution. These findings suggest that propagation pathways in the cortex as well as generation mechanism differ between spike and slow wave components.
46. The estimation of the electrical sources of the focal spike and slow wave complex using the SSB dipole tracing method. - T. Shibata, H. Iwasa, T. Ito, K. Koseki, T. Saiga, Y. Nakajima and T. Sato (Chiba) We estimated the electrical source generators of the spike component and the slow wave component of a focal spike and slow wave complex (SWC) as equivalent current dipoles (ECD). Five patients with localization-related epilepsy were analyzed: 4 with frontal lobe epilepsy (FLE) and 1 with temporal lobe epilepsy (TLE). We used the dipole tracing method using a realistic 3-shell head model called scalp-skull-brain model dipole tracing (SSB-DT; Homma et al., Electroenceph. clin. Neurophysiol., 1994, 91: 374-382). The ECDs corresponding to the spike component were estimated in a restricted area, located in the frontal lobe in the case of FLE and in the temporal lobe in the case of TLE. The ECDs corresponding to the slow wave component were estimated in a
widespread location in an ipsilateral hemisphere of the ECD of the spike component. The ECDs of the spike component were surrounded by the ECDs of the slow wave component. These results suggest that the primary epileptic activity in a small brain region followed by electrical activity in the surrounding area might be responsible for the generation of the focal SWC of scalp EEG. 47. Magnetic fields of focal motor seizure by jerk-locked averaging. - R. Hiraiwa, Y. Watanabe, K. Fukao, H. Kubota, S. Yamamoto, K. Yagi and M. Seino (Shizuoka) Jerk-locked averaged fields (JAF) triggered by focal motor seizure were examined in 2 patients with epilepsy to identify the localization of cortical excitability related to the ictal motor manifestation. Compared with movement-related magnetic fields (MRMF) in a healthy volunteer as a control, and also with the results reported by other authors, some differences were found. In one case, the JAF spike preceded about 40 msec the peak of EMG from the right short flexor muscles of the thumb associated with the focal motor seizure event. The spike appeared obviously earlier than motor fields (MF) in MRMF. The other case showed a JAF spike about 10 msec prior to the peak of EMG from the left orbicular muscles affected by twitching. The latency between the JAF spike and the muscle contraction potentials was similar to MF; however, there were no distinct movement-evoked fields observable, probably due to the concurrent irregular slow wave components. In both cases, dipole localization of the JAF spike was estimated slightly deeper than the surface of primary motor cortex. In conclusion, it is likely that not only MRMF arise in the primary motor cortex, but various other epileptic activities also participate during focal motor seizure.
48. The ct 2-agonist clonidine facilitates the development of amygdaloid kindling in infant rats. - S. Katayama, S. Yoshioka, K. Matsuda, H. Mitani, S. Matsunaga, J. Takasu, M. Sunami and R. Kawahara (Tottori) Although administration of clonidine, a noradrenergic a2-agonist, significantly retards the development of amygdaloid kindling in adult rats, the effect of the drug on infant rats is still unclear. In order to clarify this issue, we compared the process of rapid kindling between 14-day-old rat pup groups to which various doses of clonidine were administered with or without oc2-antagonists. A significant facilitation of kindling development was observed in the groups receiving high doses of clonidine (0.2 and 0.4 m g / k g , s.c.). The facilitation effect seemed to occur during both the early and the later kindling stages. Also, the cumulative afterdischarge durations, which indicate the enhancement of seizures, were significantly prolonged in the above 2 groups. These effects were not observed in the groups with combined administration of clonidine and an a2-antagonist such as yohimbine (1.0 m g / k g , s.c.) or idazoxan (l.0 m g / k g , s.c.). These results indicate that the effects of ot2-agonist on amygdaloid kindling in infant rats is markedly different from that in adult rats, and this phenomenon might come from the immaturity of the noradrenergic system.
Society proceedings/Electroencephalography and clinical Neurophysiology 98 (1996) 44P-52P
mental and physical relaxation day (the R condition). After each experimental day, 8 h sleep was polygraphically recorded during the night. Sleep stages were scored according to the Rechtschaffen and Kales manual. REM sleep periodicity was estimated by the binary autocorrelation function of the non-REM-REM cycle. Whereas there were no significant differences in the average REM sleep cycle length between the 3 conditions (the average cycle length was about 90 rain), there were significant differences in REM sleep periodicity. The periodicity was the highest in the R condition and the lowest in the PS condition. These results suggest that mental and physical stress during the daytime have an effect on the timing of REM sleep at night.
45. Source localization of spike and wave complexes by use of the spline-Laplacian method. - N. Hosaka, T. Inouye, K. Shinosaki, S. Toi, Y. Matsumoto and R. Ishii (Osaka) With the spline-Laplacian method, local cortical potentials can be more accurately estimated by calculating spline-generated surface Laplaclans of EEGs over the scalp. The spline-Laplacian method permits more precise localization of epileptiform discharges because of no influence of the reference electrode. EEGs were recorded from 32 electrode locations in 4 epileptic patients with generalized asymmetric spike and slow wave complexes. The EEGs were digitized at a sampling interval of 5 msec during a 3 sec period of spike and slow wave complexes. The spline-Laplacian maps over the whole scalp were successively constructed every 5 msec. The maps were further segmented in time with cluster analysis (r-means algorithm) for the 2-dimensional Fourier transform of Laplacian estimates. Several source locations, varying greatly in position, were found at each time. Cluster analysis classified 2 different patterns of source locations for each spike and slow wave component. In each hemisphere, the spike component showed a prefrontal distribution, and the slow component a fronto-central distribution. These findings suggest that propagation pathways in the cortex as well as generation mechanism differ between spike and slow wave components.
46. The estimation of the electrical sources of the focal spike and slow wave complex using the SSB dipole tracing method. - T. Shibata, H. Iwasa, T. Ito, K. Koseki, T. Saiga, Y. Nakajima and T. Sato (Chiba) We estimated the electrical source generators of the spike component and the slow wave component of a focal spike and slow wave complex (SWC) as equivalent current dipoles (ECD). Five patients with localization-related epilepsy were analyzed: 4 with frontal lobe epilepsy (FLE) and 1 with temporal lobe epilepsy (TLE). We used the dipole tracing method using a realistic 3-shell head model called scalp-skull-brain model dipole tracing (SSB-DT; Homma et al., Electroenceph. clin. Neurophysiol., 1994, 91: 374-382). The ECDs corresponding to the spike component were estimated in a restricted area, located in the frontal lobe in the case of FLE and in the temporal lobe in the case of TLE. The ECDs corresponding to the slow wave component were estimated in a
widespread location in an ipsilateral hemisphere of the ECD of the spike component. The ECDs of the spike component were surrounded by the ECDs of the slow wave component. These results suggest that the primary epileptic activity in a small brain region followed by electrical activity in the surrounding area might be responsible for the generation of the focal SWC of scalp EEG. 47. Magnetic fields of focal motor seizure by jerk-locked averaging. - R. Hiraiwa, Y. Watanabe, K. Fukao, H. Kubota, S. Yamamoto, K. Yagi and M. Seino (Shizuoka) Jerk-locked averaged fields (JAF) triggered by focal motor seizure were examined in 2 patients with epilepsy to identify the localization of cortical excitability related to the ictal motor manifestation. Compared with movement-related magnetic fields (MRMF) in a healthy volunteer as a control, and also with the results reported by other authors, some differences were found. In one case, the JAF spike preceded about 40 msec the peak of EMG from the right short flexor muscles of the thumb associated with the focal motor seizure event. The spike appeared obviously earlier than motor fields (MF) in MRMF. The other case showed a JAF spike about 10 msec prior to the peak of EMG from the left orbicular muscles affected by twitching. The latency between the JAF spike and the muscle contraction potentials was similar to MF; however, there were no distinct movement-evoked fields observable, probably due to the concurrent irregular slow wave components. In both cases, dipole localization of the JAF spike was estimated slightly deeper than the surface of primary motor cortex. In conclusion, it is likely that not only MRMF arise in the primary motor cortex, but various other epileptic activities also participate during focal motor seizure.
48. The ct 2-agonist clonidine facilitates the development of amygdaloid kindling in infant rats. - S. Katayama, S. Yoshioka, K. Matsuda, H. Mitani, S. Matsunaga, J. Takasu, M. Sunami and R. Kawahara (Tottori) Although administration of clonidine, a noradrenergic a2-agonist, significantly retards the development of amygdaloid kindling in adult rats, the effect of the drug on infant rats is still unclear. In order to clarify this issue, we compared the process of rapid kindling between 14-day-old rat pup groups to which various doses of clonidine were administered with or without oc2-antagonists. A significant facilitation of kindling development was observed in the groups receiving high doses of clonidine (0.2 and 0.4 m g / k g , s.c.). The facilitation effect seemed to occur during both the early and the later kindling stages. Also, the cumulative afterdischarge durations, which indicate the enhancement of seizures, were significantly prolonged in the above 2 groups. These effects were not observed in the groups with combined administration of clonidine and an a2-antagonist such as yohimbine (1.0 m g / k g , s.c.) or idazoxan (l.0 m g / k g , s.c.). These results indicate that the effects of ot2-agonist on amygdaloid kindling in infant rats is markedly different from that in adult rats, and this phenomenon might come from the immaturity of the noradrenergic system.