PubMed Health⌕ Search

Biomedical subjects

R Tarnecki

Publications and source records attributed to R Tarnecki.

17 recordsLinked to original sources
PubMed1992

[Brain mapping in atonic epileptic attacks with consciousness disorders at school age].

The paper presents the results of the analysis of atonic epileptic seizures with application of brain mapping eeg. The views to date on the pathogenesis of atonic seizures could be based on the assumptions of centrencephalic epilepsy voiced by Penfield and Jasper. The present investigations and electrophysiological-clinical observations support, however, contrary to the concept of Penfield and Jasper, the cortical origin of these seizures. The discussion on the clinical forms of atonic seizures in epilepsy, confirmed by analysis of brain mapping in the domain of frequencies and amplitude distribution, in the form of brain topograms, allows for the concept of cortical origin of these seizures with the probability of localisation of the epileptic focus, as in here presented case, in the anterior right paramedial frontal region of the brain.

Adolescent↗
PubMed1992

[Brain mapping in Parkinson disease treated by cryothalamotomy].

Brain mapping of the cerebral bioelectric activity was done by the BEAM method in 20 patients with Parkinson's disease treated by cryothalamotomy. Conventional egg examinations demonstrating relatively small changes of the type of local asymmetry of frequencies and/or amplitudes, sporadic focal changes, and sporadic generalized and disseminated generalized changes were analysed in a computer system in the domain of frequency and time. Brain mapping demonstrated very distinctly the asymmetry in the frequency bands alpha and beta. On the operated side a regular alpha rhythm of lower frequency but higher amplitude dominated in the brain hemisphere. On the intact side a quick beta rhythm prevailed and an irregular alpha rhythm was noticeable. This phenomenon described by analysis in the domain of frequency confirms the unilateral synchronizing influence of thalamotomy on the bioelectric activity of the operated brain hemisphere and may correlate with the functional motor improvement noted in the operated subjects. In three cases with a longer course of the disease analysis in the frequency domain demonstrated the presence of generalized diffused slow waves in both frontal regions. These changes correlated with mental insufficiency of the examined patients.

Adult↗
PubMed1991

Multiple spike-train analysis using mutual interval matrix.

The principal-component approach is applied to the analysis of sequences of neuronal action potentials (spike trains). Multiple spike trains are represented as a sequence of vectors of mutual interspike intervals and are considered to be part of the trajectory of a dynamic system. The trajectory matrix is decomposed into a number of 'basic spike patterns' and their relative magnitudes by singular-value decomposition. The representation provides a convenient framework for analysis of dynamic relations and cooperation between neurons in an observed network. Examples of applications to simulated and cerebellar data are presented.

Action Potentials↗
PubMed1991

Excitatory responses of the dorsal root discharge to stimulation of cutaneous and muscle afferents in the cat.

Excitatory responses of the dorsal root discharge (DRD) consisting in transient increase in its frequency have been studied in non-anaesthetized low spinal cats. They were evoked by stimulation of cutaneous nerves (superficial peroneal and posterior tibial) and muscle nerves (gastrocnemius-soleus and posterior biceps-semitendinosus), recorded from the central cut ends of single fibres of L7 dorsal roots. The excitatory responses were elicited by single volleys in low threshold cutaneous and group II muscle afferents. Group III afferents of gastrocnemius-soleus nerve were also effective. Increase in strength of stimulation of posterior biceps-semitendinosus nerve from 4T to 40T which activated group III muscle afferents significantly decreased the excitatory effects of the DRD. Incidence of excitatory responses of the DRD to volleys both in low and high threshold cutaneous afferents, was 100%. Frequency of occurrence of excitatory effects to volleys in group II muscle afferents ranged from 23% to 43% (for responses to posterior biceps-semitendinosus and gastrocnemius-soleus volleys, respectively). It was increased to 47% and 72% when excitatory effects were elicited by group III afferent volleys. These findings indicate that only some types of afferent fibres evoke excitatory responses of the DRD. Variable incidence of the excitatory responses to stimulation of cutaneous and muscle afferents suggests important difference in effectiveness of connections between both types of fibres and interneurones generating the DRD.

Action Potentials↗
PubMed1979

Interaction of peripheral and cerebellar inputs to red nucleus neurons.

In chloralose anesthetized cats responses of red nucleus neurons to cerebellar cortical or peripheral stimulation are described. Interactions between cerebellar (conditioning) and peripheral (test) stimulations were studied at various interstimulus intervals. Peripheral stimulation alone typically evoked a complex response consisting of an early (15 ms latency) burst, a period of depression of activity (inhibition, lasting up to 300 ms) and a late, long-lasting (on an average 300 ms) excitation. Cerebellar cortical stimulation resulted in a similar pattern of response; but it was composed predominantly of only two phases, an initial inhibition followed by a prolonged late discharge. With conditioning- testing intervals in a range of 10-150 ms, depending on the cell, there was a conspicuous depression of the sh0i.t-latency test excitation, followed by a prominent potentiation of this component. An occlusion of the inhibitory or late excitatory responses occurred when conditioning-testing stimuli were applied with an interval shorter than 0.5 s. It is suggested that the early excitation and the subsequent late components are generated in the red nucleus by independent mechanisms. The initial depression of the early test response is explained as an effect of Purkinje cell inhibition, and the later potentiation as a result of temporary blockage of the cerebellar cortex to afferent input.

Animals↗
PubMed1978

Single unit responses to moving spots in the superior colliculus of the cat's isolated midbrain.

The midbrain was isolated from the pons and forebrain by two brainstem transections, pretrigeminal and "preoptic", inclined at 32 degree or 35 degree to the vertical plane. The preoptic transection passed along the rostral border of the optic tract, leaving it and the chiasm intact. Thus, direct visual input into the isolated tissue was maintained. Single unit responses to a moving spot were investigated in the superior colliculus. This stimulus evoked vigorous responses in most cells. Of the 70 tested units, 25 showed direction-selectivity, 48 speed-selectivity and 47 reacted to diffuse flash. Compared to cats with only pretrigeminal transection only the number of direction-selective units was reduced. The reduction was similar to that found previously in cats with ablated visual cortex or visually deprived from birth. Thus, the cells of the isolated superior colliculus show a striking degree of functional integrity.

Action Potentials↗
PubMed1977

Interaction of converging peripheral and cerebellar cortical inputs on interpositus neurons of the cat.

Anesthetized and immobilized cats were used. The interval between the peripheral (conditioning) and the cortical (testing) stimulation equalled the latency of the response to effective peripheral input. Efferent nuclear neurons were identified by antidromic stimulations from contralateral brainstem nuclei. Various sequences of excitation and inhibition of different duration were induced by peripheral inputs. Initial excitation was observed in efferent neurons in cases of selective reactions to one of the peripheral stimulations. In some neurons both initial excitation and inhibition were observed. Besides selective reactions, in neurons with background activity a convergence of different peripheral inputs was seen. Responses to converging peripheral influences had usually a similar pattern of PSTH, with the shortest latent period to the dominant afferent input. Effects of cerebellar cortical stimulation were observed in nuclear neurons, both efferent and intranuclear. Effects of cortical stimulation were evoked from a limited area of the stimulated cortical surface; convergence and divergence of influences were observed. Peripheral and cortical stimulations induced various patterns of impulse activity of nuclear neurons. Interaction of converging peripheral and cortical inputs on a nuclear neuron was determined by the level of excitation or inhibition evoked by the peripheral stimulus and the phase of the cortical action (inhibition or "disinhibition"). Besides its participation in integrative processes at the nuclear level, the cerebellar cortex determines the duration and frequency of successive onsets of excitatory bursts at the "output" of the cerebellum, thus playing a decisive role in the coding of information to other structures of the brain.

Animals↗
PubMed1976

Effects of binocular deprivation of pattern vision on single unit responses in the cat superior colliculus.

Single unit responses in the superior colliculus of cats deprived of pattern vision from birth and of normally reared cats were studied in unanesthetized pretrigeminal preparations. Collicular units of deprived cats showed a diminished direction-selectivity but a somewhat better speed-selectivity compared to normals; they also preferred lowspeed stimuli, and reacted less frequently to diffuse flash. The impairment of direction-selectivity of collicular neurons may be partly responsible for the impairment of the pursuit eye movements in visually deprived cats.

Animals↗
PubMed1975

Response of cat cerebellar vermis induced by sound. I. Influence of drugs on responses of single units.

Experiments were done on the cats under Chloralose and/or Nembutal anesthesia. A click was used as a standard acoustic stimulus. The type of responses of single units from cerebellar vermis lobuli V-VII were analyzed. At least four different types of single unit reactions were observed and one of these - oscillatory - was produced by the presence of Flaxedil simultaneously with Chloralose. The system that controls the activity of the middle-ear-muscles can be suspected as the source of the oscillatory pattern of the cerebellar response. Latencies were found to be constant, independent of anesthesia, but it was necessary to have a low level of Nembutal anesthesia because of the overriding inhibitory influence of Nembutal.

Acoustic Stimulation↗
PubMed1975

Response of cat cerebellar vermis induced by sound. II. The role of the mossy and climbing fibers in acoustic transmission to the cerebellar cortex and influence of stimuli parameters.

Experiments were performed on cats under Chloralose or Nembutal anesthesia. The parameters of the acoustic click stimuli were found to have a strong influence on the responses registered from both the surface of the cerebellar vermis lobuli V up VII as well as from single units. It was shown that a stimulus frequency rate not greater than 1/2 s should be used, since higher frequencies caused strong attenuation of the response. The type of anesthesia did not change the latencies of reactions of both evoked potentials and single units. However, decreasing the strength of the click resulted in increased response latencies, in the case of single unit reactions. A very strong influence of weak visual stimuli on units was also observed. It is suggested that mossy fibers are the most important fibers in the transmission of acoustic information to the cerebellar cortex.

Acoustic Stimulation↗
PubMedDate not supplied

Functional connections between neurons of interpositus nucleus of the cerebellum and the red nucleus.

Patterns of functional connections between individual neurons of nucleus interpositus (IP) of the cerebellum and red nucleus (RN) were examined. This was assessed by cross-correlation of spike trains characterizing interaction between simultaneously recorded neurons. Direct interpositorubral connections were always excitatory in nature: direct inhibition was only found within and not between these nuclei. Shared inputs from common sources outnumber other types of interpositorubral connections. Patterns of connection between IP RN neurons could be influenced by sensorimotor cortex.

Afferent Pathways↗
PubMedDate not supplied

Functional relations between neighboring neurons of nucleus interpositus of the cat cerebellum.

In the nucleus interpositus (IP) of the cat cerebellum the response patterns to peripheral stimulation were recorded, and the interactions between electrophysiologically identified neurons were studied with cross correlation techniques. The response patterns were composed of excitation appearing with latencies of about 8 to 22 ms., separated and succeeded by phases of inhibitions. Four basic types of interneuronal connectivities were observed: 1) intranuclear excitation, 2) shared input from a common source, 3) intranuclear inhibition, and 4) stimulus coordinated firing. Shared input appeared in all combinations of paired neurons and extended for a distance from 300 microns up to 1000 microns. Intranuclear excitation as well as inhibitory synaptic connection occurred mainly in combinations between interneurons and efferent neurons. Stimulus coordinated firing of paired neurons was found in almost the entire extent of the nucleus interpositus.

Animals↗
PubMedDate not supplied

Correlations of neuronal spike discharges of VL neurons during spontaneous firing and during the activity evoked by peripheral stimulation.

The temporal relations between simultaneously recorded neurons of the nucleus ventralis lateralis (VL) of cat thalamus were studied. The interaction and the functional connections between individual VL neurons are described. This was achieved with an application of cross correlation techniques. The response patterns of different individual neurons to somatic sensory and photic stimuli were also analyzed. For the purpose of classifying neurons as thalamocortical relay cells (T-C) and non relay cells (N-C) which do not project to the motor sensory cortex antidromic cortical stimulation was used. This stimulation was also used as conditioning one when proceeded peripheral stimuli. To analyze the nonspecific specific interactions upon single neurons conditioning photic stimuli were applied. The results show that T-C neurons are antidromically excited from a wide cortical areas and that the functional interaction between T-C neurons is mediated by a shared input from common sources. It is further postulated that N-C cells interposed between relay neurons subserve the functions of gating units modifying the neuronal network of lateral ventral nucleus of the thalamus.

Action Potentials↗