Spike-wave complexes and fast components of cortically generated seizures. III. Synchronizing mechanisms.
نویسندگان
چکیده
The intracortical and thalamocortical synchronization of spontaneously occurring or bicuculline-induced seizures, consisting of spike-wave (SW) or polyspike-wave (PSW) complexes at 2-3 Hz and fast runs at 10-15 Hz, was investigated in cats under ketamine-xylazine anesthesia. We used single and dual simultaneous intracellular recordings from cortical areas 5 and 7, and extracellular recordings of unit firing and field potentials from neocortical areas 5, 7, 17, 18, as well as related thalamic nuclei. The evolution of time delays between paroxysmal depolarizing events in single neurons or neuronal pools recorded from adjacent and distant sites was analyzed by using 1) sequential cross-correlations between field potentials, 2) averaged activities triggered by the spiky component of cortical SW/PSW complexes, and 3) time histograms between neuronal discharges. In all instances, the paroxysmal activities recorded from the dorsal thalamus lagged the onset of seizures in neocortex. The time lags between simultaneously impaled cortical neurons were significantly smaller during SW complexes than during the prior epochs of slow oscillation. During seizures, as during the slow oscillation, the intracortical synchrony was reduced with increased distance between different cortical sites. Dual intracellular recordings showed that, during the same seizure, time lags were not constant and, instead, reflected alternating precession of the recorded foci. After transection between areas 5 and 7, the intracortical synchrony was lost, but corticothalamocortical volleys could partially restore seizure synchrony. These data show that the neocortex leads the thalamus during SW/PSW seizures, that time lags between cortical foci are not static, and that thalamus may assist synchronization of SW/PSW seizures after disconnection of intracortical synaptic linkages.
منابع مشابه
Mircea Steriade , Florin Amzica , Dag Neckelmann and Igor Timofeev Generated Seizures . II . Extra - and Intracellular Patterns Spike - Wave Complexes and Fast Components of Cortically
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Spike-wave complexes and fast components of cortically generated seizures. II. Extra- and intracellular patterns.
In the previous paper we have demonstrated, by means of field potential and extracellular unit recordings, that bicuculline-induced seizures, which include spike-wave (SW) or polyspike-wave (PSW) complexes, are initiated intracortically and survive ipsilateral thalamectomy. Here, we used multisite field potential and extracellular recordings to validate the patterns of cortical SW/PSW seizures ...
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متن کاملSpike-wave complexes and fast components of cortically generated seizures. I. Role of neocortex and thalamus.
We explored the relative contributions of cortical and thalamic neuronal networks in the generation of electrical seizures that include spike-wave (SW) and polyspike-wave (PSW) complexes. Seizures were induced by systemic or local cortical injections of bicuculline, a gamma-aminobutyric acid-A (GABAA) antagonist, in cats under barbiturate anesthesia. Field potentials and extracellular neuronal ...
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عنوان ژورنال:
- Journal of neurophysiology
دوره 80 3 شماره
صفحات -
تاریخ انتشار 1998