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Biomedical subjects

L Kellényi

Publications and source records attributed to L Kellényi.

18 recordsLinked to original sources
PubMed1990

Somatosensory evoked potentials elicited by stimulation of the posterior tibial nerve in patients with multiple sclerosis.

Normal control somatosensory evoked potential data (elicited by stimulation of the posterior tibial nerve), of 20 healthy subjects were compared to the electrophysiological data of 20 patients with the diagnosis of definite or probable multiple sclerosis. The demyelinating process affects all segments of the response, causing increase in latency and decrease in amplitudes as well as lack of the potentials during the disease. Based on the literature, the neurological localization values of TPSEP are summarized. Due to its outstanding sensitivity in these cases, the procedure as advised by the authors should be used in demyelinating processes and in other spinal cord disease of different aetiology.

Adult↗
PubMed1987

Behavioral dependence of the electrical activity of intracerebrally transplanted fetal hippocampus.

Adult rats with unilateral aspirative lesions of the fimbria-fornix and the overlying cingulate cortex received implants of 17-day-old fetal hippocampal tissue in the lesion cavity, placed to form a tissue bridge across the cavity. From 6 to 8 months later they were equipped with chronic recording and stimulating electrodes in the transplant and the host brain. The dominant electrical pattern of the graft consisted of irregularly occurring sharp waves (SPW) or EEG spikes of 30-150 ms duration and concurrent synchronous neuronal bursts of large cell populations. SPWs occurred during all behaviors but their frequency was significantly lower during running than during drinking. Population bursts of neurons in the graft could be evoked by stimulating either the ipsilateral host hippocampus or the perforant path. Both complex spike cells and single spike cells could be recorded from the graft. The discharge frequency of single spike cells was considerably higher during running than during drinking or immobility. Some of the single spike cells in the graft fired rhythmically at 6-9 Hz during running and walking, and phase-locked with the rhythmic slow EEG activity (theta, theta-EEG) recorded from the intact host hippocampus. Occasionally field theta-EEG was also present in the graft. These findings suggest that at least a portion of the graft neurons had come under the control of the host brain, and by way of the newly established host-graft connections the activity of some graft neurons was regulated in a near-normal manner.

Animals↗
PubMed1986

Laminar distribution of hippocampal rhythmic slow activity (RSA) in the behaving rat: current-source density analysis, effects of urethane and atropine.

This study investigated the laminar distribution of rhythmic slow wave activity (RSA) in the dorsal hippocampus of the rat during running. Depth analyses of field EEG were performed by stepping the recording electrode in 82.5 micron increments and sampling RSA at each depth. One-dimensional current-source density (CSD) was calculated from the RSA profiles to enhance spatial resolution of current sources and sinks. Laminar analysis of power, coherence, and phase of RSA with respect to a stationary electrode in the stratum oriens of CA1 was performed with spectral methods. RSA waves in the CA1-dentate axis had power maxima at about the hippocampal fissures, hilus, outer molecular layer of the endal leaf of dentate gyrus and stratum oriens of CA1, in that order. A gradual shift of phase occurred in stratum radiatum of CA1. Large phase-shifts were found in both the endal and ectal leaves of the fascia dentata. A null zone and associated sudden phase-reversal of RSA were observed in stratum lucidum of CA3. Multiunit activity showed phase-locked modulation with RSA in the granule cell layer of the dentate gyrus and pyramidal cell layer of CA1, CA3, and subiculum. CSD analysis in the CA1-dentate axis revealed multiple source-sink pairs. The sinks and sources showed cyclic changes with RSA, and were attributed to the rhythmic, but time-shifted, activity of hippocampal afferents from the septum and entorhinal cortex. The gradual phase-shift in CA1, and the configurational changes of RSA waves with depth, are explained by the summation of extracellular currents produced by time-delayed sink-source pairs (RSA dipoles). When the cholinergic septohippocampal path was blocked by atropine a null zone in the middle of stratum radiatum of CA1 occurred and the phase-shift of RSA became steeper. Under urethane anesthesia a null zone was present in the inner stratum radiatum associated with a sudden phase-reversal of RSA. Urethane reduced the power of RSA in the hilus and decreased the firing rate of the granule cells. It is suggested that field RSA is produced by several rhythmical dipoles along the somadendritic surface of pyramidal cells and granule cells and the spatiotemporal relations of the individual dipoles determine the actually observed extracellular RSA.

Anesthesia, General↗
PubMed1985

Bone growth accelerated by stimulation of the epiphyseal plate with electric current.

The effect of stimulation with continuous small amounts (20 microA) of electric current on the distal epiphyseal plate of rabbit femurs was examined. In contrast to control animals 6 weeks after the operation 18 of the 20 experimental animals showed an increased lengthening or broadening of the femur on the operated side. In 14 cases the increased growth resulted in varus or valgus deformities.

Animals↗
PubMed1985

Depth profiles of hippocampal rhythmic slow activity ('theta rhythm') depend on behaviour.

Wave shape patterns and spectral properties of hippocampal slow wave activity (RSA) were studied in behaving rats equipped with stationary recording/stimulating electrodes and a movable microelectrode. RSA waves had maximum power at about the hippocampal fissure, and two minima just below the pyramidal cells of CA1 and the inner molecular layer of the dentate gyrus, respectively. The phase profile of RSA was gradual during both running and lever pressing, but the two profiles showed phase differences in the stratum radiatum of CA1 and the hilus. Averaged RSA waves consisted of fast rising and slow decaying components, giving a saw-tooth like pattern. RSA waves were more asymmetric during running than during lever pressing. The slow component showed a sudden polarity reversal below the pyramidal layer of CA1. The fast component of RSA showed a gradual shift and change of the slope with depth. An additional small amplitude wave riding on the slow component ('notch') was present during running. The amplitude increase of the 'notch' occasionally caused frequency doubling of RSA and consequent high power of the second harmonic. The gradual shift and change of the fast component are explained by the hypothesis that somatic inhibitory and dendritic excitatory RSA dipoles in CA1 and dentate gyrus are active at different times of the RSA cycle.

Animals↗
PubMed1981

Hippocampal slow wave activity during appetitive and aversive conditioning in the cat.

The electrical activity of the dorsal and ventral divisions of the hippocampus was investigated quantitatively during the development of discriminative operant training and defensive conditioning. Signal-related (respondent, sign-tracking) and goal-directed (operant, 'voluntary') activities and their hippocampal electrical correlates were compared. Signal-related behaviour was accompanied by significantly higher frequency spectral peaks than lever press behaviour. Spectral peaks were higher during lever pressing in early stages of training as compared to criterion performance. In defensive conditioning overt sign-tracking behaviour disappeared but spectral peak shifts toward higher values upon signal presentation persisted. Comparison of dorsal and ventral hippocampal activity revealed high coherence values and similar frequency shifts during behaviour transitions. These findings argue against suggestions that a close relationship exists between elementary motor acts and hippocampal EEG.

Animals↗
PubMed1979

Dynamic phase-shifts between theta generators in the rat hippocampus.

Winson [13] reported on two independent phase-reversed generators in the rat hippocampus. In the present study the synchrony between the two generators was investigated during the sleep-wakefulness cycle and during a behaviour-dependent discriminative learning task. Electrical activities derived from the CA 1 region and dentate gyrus were in phase during slow wave sleep but phase-reversed during the awake state and paradoxical sleep. The degree of phase-reversal was significantly higher during running than during lever pressing. These findings demonstrate that substantial changes occur within the hippocampal circuitry during dynamic shifts of behaviour.

Animals↗
PubMed1977

Simple device for the tape recording of complex behavioral situation on one track.

A low cost electronic device is described to record on one a.m. tape track the occurrence of any combination of four signals. The fast read out of recorded signals makes the apparatus reliable and helpful for coding behavioral situation and automatic averaging of event related phenomena. A detailed circuitry is included and discussed.

Electrophysiology↗
PubMedDate not supplied

[Evoked potentials during the elaboration of a conditioned reflex to hippocampal stimulation in rats].

In experiments on 9 rats, the study of evoked potentials (EPs) of the CA1 field of the dorsal hippocampus to stimulation of its symmetrical part serving as a signal of drinking conditioned reflex (CR) showed that during reflex elaboration, the amplitude of the main EP components significantly decreased; CR did not appear when the population spike (PS) was absent in the hippocampal response. PS always accompanying CR was not specific only of it, it was also recorded at other behavioural reactions. Changes of fascia dentata EPs in the process of CR elaboration to stimulation of its symmetrical part consisted in decrease of the initial negative wave and increase of the positive one. The obtained data point to a significant reconstruction of excitatory and inhibitory inputs to the hippocampus and fascia dentata under the influence of conditioned activity.

Animals↗