Increased expression of GABA(A) receptor beta-subunits in the hippocampus of patients with temporal lobe epilepsy.

It has been postulated that dysfunction of the GABA-ergic transmission is causatively related to the development of epilepsy. Animal models of temporal lobe epilepsy (TLE) revealed considerable changes in the expression of GABA(A) receptor subunits in the hippocampus. Using immunocytochemistry, we investigated the expression of GABA(A) receptor subunits alpha1, alpha3, beta1-3, and gamma2 in hippocampal specimens obtained at surgery from TLE patients with and without hippocampal sclerosis and in autopsy controls.

Memantine for prevention of spinal cord injury in a rabbit model.

Background: This study was conducted to investigate the effect of memantine, a noncompetitive N-methyl-d-aspartate receptor antagonist, on the neurologic outcome of spinal cord ischemia after aortic occlusion.

Materials And Methods: New Zealand White rabbits were anesthetized and spinal cord ischemia was induced for 40 minutes by infrarenal aortic occlusion. Animals were randomly allocated to 3 groups.

Nonlinear analysis of epileptic activity in rabbit neocortex.

We report on the nonlinear analysis of electroencephalogram (EEG) recordings in the rabbit visual cortex. Epileptic seizures were induced by local penicillin application and triggered by visual stimulation. The analysis procedures for nonlinear signals have been developed over the past few years and applied primarily to physical systems.

Sources of electric brain activity: intracortical current dipoles.

Intracortical evoked potentials after electrical stimulation of the optic nerve were simultaneously recorded from the different layers of the rabbit's visual cortex. The averaged potentials were subjected to current source density analyses. The results show that the first event after the stimulus is a current sink in layer VI according to the excitatory terminations of the specific afferent fibres of the geniculate body.

Electrophysiological and morphological properties of rat motor cortex neurons in vivo.

This paper describes results obtained from intracellular recordings and stainings of motor cortex neurons in the rat in vivo. Rats were anesthetized with phenobarbital. Neurons were intracellularly recorded with micropipettes filled with K+-methylsulphate + 4% HRP in phosphate buffer (pH 7.

An approach to a synopsis of EEG parameters, morphology of brain convolutions and mental activities.

A method for the projection of EEG data on the brain surface is proposed. The EEG data are obtained during the performance of mental tasks and represented as probability maps of power and coherence changes with respect to the averaged EEG at rest. The morphological data are obtained from 3D reconstructions of the brain by means of serial slices provided by an MRI scanner.

[Focal epilepsy: generation and spreading mechanisms in experimental conditions].

This paper describes essential mechanisms underlying focal epileptic activity. Within the centre of an epileptic focus neurons display a characteristic phenomenon - the paroxysmal depolarization shift. This type of activity is partly caused by membrane-intrinsic mechanisms and also by postsynaptic excitation.

High resolution multi-temperature sensors for biomedical application.

A temperature sensor array was designed in order to study local temperature variations and temperature gradients in biological samples. The sensor probe was inserted in the optical cortex of rabbits in order to study temperature changes during normal brain activity as well as under artificial ventilation conditions. Temperature sensitive areas of 0.

Pathophysiological aspects of dysphoric states.

Dysphoric states have been of particular interest for a long time since they occur not only in patients with psycho-organic syndromes but also in those with manic-depressive disease. This paper discusses some aspects of dysphoria from the pathophysiological point of view. Data mostly derived from epileptic patients indicate the critical role the limbic system plays in the control of emotions.

Paroxysmal neuronal depolarizations in the rat motorcortex in vivo: intracellular injection of the calcium agonist BAY K 8644.

Epileptic activity was elicited in the rat's motor cortex by local application of penicillin. At the neuronal level it consisted of typical paroxysmal depolarization shifts. The calcium agonist BAY K 8644 was injected into neurons showing such a discharge pattern.

[Music perception, EEG and musical training].

Changes of EEG during listening to music were studied in two groups of probands, one of them with several years of training on a musical instrument. The EEG was recorded simultaneously from 19 electrodes (10:20 system) against connected ear lobe electrodes. One minute recording periods at rest before and after music were compared with a period of one minute recording during listening to music.

On-going EEG in depression: a topographic spectral analytical pilot study.

Spontaneous EEG activities recorded with 19 electrodes (10-20 system) on the scalp were quantified by spectral analytical methods (power and coherence spectra) to reveal changes of power and coherence during different conditions (eyes closed/relaxed, eyes opened/relaxed, flicker stimulation, reading, listening to a story). Control subjects and depressive patients were compared. Power as well as coherence changes were found in all frequency bands.

Penicillin-induced epileptic phenomena in the rabbit's neocortex II. Laminar specific generation of interictal spikes after the application of penicillin to different cortical depths.

To elucidate the generation mechanisms of interictal spikes we analyzed the electrical events in the different layers of the rabbit's neocortex after application of penicillin to distinct cortical layers. Field potentials (FP) recorded simultaneously from all layers with a 16-fold micro-electrode-assembly were subjected to current-source-density analysis (CSD), which allows a more accurate description of local electrical events. To demonstrate the influence of neocortical architectonics on the generation of interictal spikes, 3 different areas-area occipitalis 1, precentralis 1 and 2, according to Fleischhauer et al.

Penicillin-induced epileptic phenomena in the rabbit's neocortex I. The development of interictal spikes after epicortical application of penicillin.

In an attempt to elucidate the generation mechanisms underlying interictal spikes in the neocortex, the temporal development of spikes after the epicortical penicillin (PNC) application was studied. Field potentials (FP) were recorded simultaneously within the 6 neocortical layers with a multielectrode consisting of 16 contacts (10 X 10 micron 2) in a row at spacings of 150 micron. A one-dimensional current-source-density (CSD) analysis yielded the positions of current, sink and source densities, so that the different electrical events during a spike could be more accurately located within the different neocortical layers.

Computer-assisted EEG topography as a tool in the evaluation of actions of psychoactive drugs in patients.

This paper summarizes a tentative application of EEG topography to the evaluation of the efficiency of psychoactive drugs. It shows that the spectral content of the EEG, recorded simultaneously at different locations according to the international 10-20 system, is a sensitive measure for the quantification of drug activity. Furthermore, coherence analysis reveals differences in the functional organization of the neocortex under neuroleptic drug therapy.

[Mechanism of the generation of evoked potentials in the rabbit neocortex].

This paper describes the analyses of evoked potentials recorded in different neocortical areas (Area precentralis 1 and 2, occipitalis 1 and 2) and elicited by different stimulation techniques (antidromic stimulation of the pyramidal tract, electrical stimulation of thalamic nuclei, the optic nerve and finally random dot stimulation of the retina). Field potentials were recorded intracortically with a 16-fold electrode. The analyses of field potentials with the current-source-density method yielded an estimation of the current source and sink density distributions within the six neocortical layers.

The contribution of the cortical layers to the generation of the EEG: field potential and current source density analyses in the rabbit's visual cortex.

Intracortical spontaneous field potentials (EEG) were simultaneously recorded from the different layers of the rabbit's visual cortex using multielectrodes produced by thin-film technology. The signals were subjected to spectral analyses. Additionally, current source density analysis was applied to spontaneous delta waves.

[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 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.

Current source density analysis: methods and application to simultaneously recorded field potentials of the rabbit's visual cortex.

This paper deals with the application of current source density (CSD) analysis to simultaneously recorded intracortical field potentials of the rabbit's visual cortex. Recordings were made with multielectrodes with either 8 contacts at distances of 300 microns, or 16 contacts at distances of 150 microns on one carrier needle. For synchronized activities, a spatial resolution of 150 microns turned out to be sufficient to record all depth-varying details of the field potentials; for seizure potentials even a spacing of 300 microns was adequate in most cases.