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Biomedical subjects

H Petsche

Publications and source records attributed to H Petsche.

At least 37 records · Page 2Linked to original sources
PubMed1981

[The effect of clonazepam on visual evoked potentials of the rabbit (author's transl)].

This paper deals with the action of Clonazepam on the cortical responses to visual stimuli in the rabbit. Epicortical as well as intracortical recordings from the different laminae were made by means of a multi-electrode made by thin film technology (13). Clonazepam was given intravenously in a dosis of 0.5 or 1.0 mg/kg body weight. The surface recordings showed that the visual evoked potentials (VEP) was, under the influence of the drug, altered only with respect to its secondary components. Those components which seem to originate within the zone of bilateral projection from both eyes are mostly influenced. The long lasting surface negative late component of the VEP was abolished by the action of the drug, and low-amplitude oscillations were seen instead. Within the different laminae of the visual cortex all components were altered in amplitude and latency. This phenomenon was most prominent within the zone of bilateral projection. Instead of two major negative components in the deep cortical layers, many positive and negative peaks were observed after the application of Clonazepam. This corresponds partly with the findings on the surface of the cortex. These results are discussed with respect to the manyfold mechanisms of action of Clonazepam.

Animals↗
PubMed1981

[Influence of clonazepam on interictal penicillin-spikes (author's transl)].

This paper deals with the action of Clonazepam on Penicillin induced interictal discharges. In 7 rabbits Penicillin was applied epicortically in a concentration of 25,000 or 50,000 I.U. The intracortical recordings were made with an 8 fold electrode, made by thin-film technology. Clonazepam (0.5 or 1.0 mg/kg) was given intravenously 30 to 45 min after the Penicillin application. Under Clonazepam the occurrence of double-und multiple interictal discharge is abolished. Single spikes become shorter and are significantly reduced in amplitude. Current Source-Density analysis showed that the configuration of sources and sinks is not altered under the action of this drug. However the spatio-temporal distribution is reduced drastically. If the shape of interictal spikes is compared by means of averaging technique before and after the application of Clonazepam, one observes a significant decrease in the standard deviation. These results indicate that excitatory processes are reduced by an enhancement of inhibitory phenomena within the cerebral cortex.

Animals↗
PubMed1978

[Neurophysiology of epileptic seizures (author's transl)].

The paper is a review of the progress made over the past years in the understanding of electrical processes occurring during epileptic seizures as elicited by the local application of penicillin. The events at the cellular level of the neocortex are discussed, as well as cortico-subcortical relationships and microtopography of the seizure patterns. The increased excitability under penicillin induces a great number of feedback processes, the electrical effects of which become visible in the seizure EEG with its high degree of organization. Neocortical architectonics is of great importance for the shape of the potentials and their distribution. Seizure patterns of different shape are found in the different layers of the cortex.

Animals↗
PubMed1978

EEG synchronization in seizures: facts and models.

In topographic studies of seizure patterns in the rabbit, the phenomenon of synchronization has turned out to be characterized by regular propagation of the potential fields underlying the raphoelements observed in the EEG: in most cases these potential fields describe circular paths within the cortex. Moreover, a multielectrode was developed to explore the different layers of the cortex simultaneously. Both approaches brought enough material to put forward a hypothesis on the origin and the maintenance of so-called synchronized activities.

Animals↗
PubMed1977

[The phenomenon of synchronization in the status epilepticus produced by penicillin and its changes after Clonazepam (author's transl)].

The purpose of this series of experiments was to understand how Clonazepam changes the mechanisms of synchronization in seizures. Penicillin was applied to the rabbits cortex. Interictal spikes and seizures were recorded with multiple electrodes from both the cortical surface and intracortically. The spatio-temporal relationships during these electrical events were studied by topographical methods. Moreover, power spectrum and coherence estimates were performed. A most characteristic feature seen with low doses of Clonazepam is a regularization of the spatio-temporal behaviour of both spikes and seizures. The number of tonic phases considerably increases at the cost of clonic phases. The seizures take more time to become generalized. The generator-zones become larger. This is explained by a decrease of the number of neurones--by Clonazepam--which are still left to produce "paroxysmal depolarization shifts". The findings confirm the increase of postsynaptic cortical inhibition under Clonazepam, as demonstrated by various authors.

Animals↗
PubMed1976

Topography of the EEG: survey and prospects.

In the first part of the paper the purpose and aims of topographical approach to the understanding of the EEG are set out. Since the EEG is not identical with the electrical activity recorded directly from its generator layer, the neocortex, topographic methods applied to the human EEG recorded from the scalp are somewhat less informative than in experimental work on the exposed brain. The paper gives a brief historical survey of the most essential attempts in this field throughout the history of electroencephalography. After this, a few promising methods now in use, and their possible fields of application, are demonstrated. The paper ends with a view of the future.

Alpha Rhythm↗
PubMed1976

[Intracortical electrogenesis: spontaneous activity, sleep and epileptic seizure (author's transl)].

Various electrical activities were recorded in rabbits from within the cortex by means of a multielectrode carrying, on a glass needle, 8 Ag-AgCl contacts (50X50 micronm) at 300 micronm distances. The records were stored on tape and analyzed (power spectrum, coherence and phase). Generally, the relatively uniform pattern of the cortical surface is paralleled by a spatio-temporally very complex intracortical activity. In all activities a zone of minimum activity ("zero zone") was found between roughly 500 and 800 micronm below surface. Beyond this zone, activities often appear like a mirrorimage of the surface activities although true phase-reversals never occur. In spontaneous activities this zone remains constant, during seizures it may shift and broaden. The maximum power is usually found below this zone. The transcortical power profile often changes during seizures. Tonic patterns, although fairly uniform in the ECoG from the surface of the cortex, turn out to be composed of several components when studied intracortically. The "generator zones" of the various intracortically identifiable graphoelements have various vertical position and extension. These findings demonstrate that a certain neuronal circuitry may be responsible for the shape of the potential recorded. This circuitry is far from rigid but may change in different stages of synchronization. For a better spatio-temporal resolution of intracortical activities, the interelectrode distance has still to be reduced.

Animals↗