PubMed Health⌕ Search

Biomedical subjects

E N Sokolov

Publications and source records attributed to E N Sokolov.

At least 19 recordsLinked to original sources
PubMed2000

Perception and the conditioning reflex: vector encoding.

Color perception is dependent on the generation of an excitation vector which, acting on a pool of color detectors (color detector map), produces a corresponding sensation. The generation of the color excitation vector starts at the retinal level, proceeds in the lateral geniculate body, and reaches color detectors at the cortical level. Following processing at the level of declarative memory and semantic maps, results in a verbal categorization of colors. Parallel to the excitation vector pathway, a network computing color differences is operating. The computation of color differences at the retinal level possibly takes place in phasic bipolar cells and progresses in the lateral geniculate body and at the cortical level. Detectors of color differences are assumed to be a basis of respective numerical estimations in humans. Data from frogs, fish, monkeys and humans are compared.

Animals↗
PubMed1999

Elementary and compound postsynaptic potentials in the defensive command neurons of Helix lucorum.

The present communication concerns with the analysis of elementary and the compound excitatory postsynaptic potentials (eEPSPs and cEPSPs) recorded by intracellular microelectrode from an identified defensive command neuron of the snail Helix lucorum. The eEPSPs were evoked by single presynaptic action potentials (APs) elicited by cationic current injection into one of the identified sensory neurons synapsing on the respective command neuron. The cEPSPs were elicited by local brief tactile stimuli on the skin or internal organs. It was shown that the cEPSPs amplitudes depend mainly on the number of activated sensory neurons. Compound EPSPs depend also on frequency and the number of APs in the bursts occurring in a single neuron. Presynaptic APs having frequency 2-10 Hz evoke high frequency depression of that eEPSPs after an interval is followed by post-tetanic potentiation of single eEPSPs. Preceding stimulation of a pneumostom area facilitates the cEPSPs elicited by repeated stimulation of viscera. The eEPSPs from the same visceral area demonstrate no heterosynaptic facilitation in experiments with double parallel intracellular recording from responsive sensory and command neurons. The different types of the eEPSPs plasticity are discussed according to their contribution cEPSPs plastic changes.

Animals↗
PubMed1993

Habituation of phasic and tonic components of the orienting reflex.

This study examined phasic and tonic measures of electrodermal activity in a simple habituation paradigm with innocuous visual stimuli. Prestimulus skin conductance levels were taken as measures of the arousal level existing at each stimulus presentation, and the subsequent electrodermal responses were taken as indices of the phasic orienting reflex (OR) elicited by each stimulus. The arousal level was considered as a tonic OR measure. Both the tonic and phasic ORs showed effects of trials. Arousal levels also showed an initial sensitization, as suggested by dual-process theory. After within-subject effects of arousal changes over trials were removed by simple regression analyses, novelty still remained as the major determinant of phasic OR magnitude. This finding is discussed in relation to the OR mechanism.

Adult↗
PubMed1989

[A dynamic model of the interaction of cones with bright horizontal cells in the carp retina].

The dynamic model showing interaction between cones and L-type horizontal cells in the carp retina is discussed. The model is based on the intracellular recording of spectral responses of horizontal cells. The model equations describe the contribution of ionic channels to responses of cones and horizontal cells. The model permits predicting responses of photopic L-cells as a function of time.

Animals↗
PubMed1988

Frequency and location specificity of the human vertex N1 wave.

Test tones of 1000 Hz subjectively located in the middle of the head were randomly presented with equiprobable intervening tones. The latter stimulus was constant within a stimulus block. The frequency of the intervening stimulus varied between different blocks from 578 Hz to 1728 Hz and its location varied in parallel with the frequency along the left-right dimension through 7 different locations. The constant inter-stimulus interval was 460 msec. The EEG was recorded at Cz and Fz. The N1 wave elicited by the test stimuli was smaller the smaller was the separation between the two stimuli in frequency or location. These results were interpreted in terms of stimulus-specifically adapted detector activity. The more the test and intervening stimuli resemble each other the greater is the overlap between the respective feature-detector populations activated and, therefore, the smaller is the N1 amplitude. Thus the sensory-specific component of the N1 wave generated in the primary auditory areas at least in part reflects detector activity. The selective frequency adaptation was much more specific in the present study than in the previous ones and suggested that the N1 component recorded was generated by highly frequency-specific neurons. The frequency and location effects were independent, i.e., the frequency effect was rather similar for different location separations, and vice versa. Thus, evidence for separate detectors for frequency and location of an auditory stimulus was obtained.

Adult↗
PubMed1987

[Double action potentials in the command neurons of Helix pomatia in response to the action of cobalt ions].

Cobalt chloride (20 mmol/l) in physiological solution results in generation of doublets of spikes in Helix pomatia command neurons in response to intracellularly injected depolarizing current. The extraspikes arise in arborizations of neuron and are determined by influx sodium ions. It is supposed that facilitation of extraspikes in apparently due to long-lasting blockade of calcium-dependent potassium current by Co2+ ions.

Action Potentials↗
PubMed1985

[Desensitization of cholinoreceptors of the somatic membrane of command neurons of Helix lucorum taurica L].

Desensitization of receptors by the rhythmic application of acetylcholine (AC) was studied in Helix lucorum command neurons PPa2, PPa3, LPa2, LPa3. Application of AC induced in them monophasic depolarization wave. Repetitive AC stimulation with intervals less than 1-2 min induced a decrement of the response which gradually reached plato. Rate and degree of desensitization were constant in every following series and did not depend on preceding periods of depression. Response restoration was unchanged if intervals between series were equal. Stimulation with higher frequencies induced more considerable desensitization. Desensitization was specific to the locus of the membrane, on which AC was applied. Extrastimulation (intracellular stimulation and application of AC) did not lead to restoration of the response. It is supposed that desensitization is a short-term process and results from changes in receptors. The obtained data are explained by means of the Katz-Thesleff model of desensitization. As certain characteristics of synaptic depression and desensitization are similar, a suggestion is put forward that postsynaptic receptors can participate in the processes of synaptic effectiveness decrement during habituation.

Animals↗
PubMed1985

[Presynaptic mechanisms of synchronizing fluctuations in the amplitude of synaptic potentials in the central nervous system of Helix lucorum taurica L].

The amplitude of EPSP arising in different command neurons (LPa2, LPa3 and PPa3) of the snail Helix lucorum after stimulation of presynaptic element LPa7 fluctuated synchronously. Synchronous application of acetylcholine on two command neurons showed that synchronous EPSP fluctuations were connected not with postsynaptic but with presynaptic mechanisms. The existence of a special modulating neuron is suggested.

Acetylcholine↗
PubMed1975

Light-sound interaction in the neurons of the rabbit's visual cortex.

One hundred cells of the visual cortex were studied using flashes, clicks and light-sound combinations with different delays. Forty nine neurons changed the total number of spikes to click stimulation. Twenty eight cells responded to clicks with specific response pattern. In 23 cells the initial discharge occurred at 60-70 ms after the onset of clicks. In 39 cells the responses to light-sound combinations differed from the responses to flashes. While 16 cells decreased their responses, the addition of sound increased firing in 23 cells. The specific modification of the light-evoked responses under acoustic stimulation were classified into three main categories: 22 cells generated new response patterns, 18 cells showed a re-distribution of peaks in the PTS histogram and three cells demonstrated a desynchronization of the spike discharge. The study of the heteromodal recovery cycle revealed that the majority of the cells increased their firing during 0-100 ms and decreased firing during 200-300 ms of the response time scale. The critical delays between light and sound, resulting in the modification of the response for the majority of the cells, were within 100 ms in both directions.

Acoustic Stimulation↗