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Biomedical subjects

S N Raeva

Publications and source records attributed to S N Raeva.

At least 19 recordsLinked to original sources
PubMed2006

The role of the parafascicular complex (CM-Pf) of the human thalamus in the neuronal mechanisms of selective attention.

The reactions of 93 neurons in the parafascicular complex (CM-Pf) of the human thalamus were studied by microelectrode recording during stereotaxic neurosurgical operations in patients with spastic torticollis. High reactivity was demonstrated for two previously classified types of neurons with identical irregular (type A) and bursting Ca2+ -dependent (type B) activities in response to presentation of relevant verbal stimuli evoking selective attention in humans. Concordant changes in the network activity of A and B neurons were observed, in the form of linked activatory-inhibitory patterns of responses and the appearance, at the moment of presentation of an imperative morpheme of the command stimulus, of rapidly occurring intercellular interactions consisting of local synchronization with simultaneously developing rhythmic oscillatory (3-4 Hz) activity. Data are presented on the existence of a direct connection between these neuronal rearrangements and activation of selective attention, providing evidence for the involvement of the thalamic parafascicular complex (CM-Pf) in the mechanisms of selective attention and processing of relevant verbal information during the preparative period of voluntary actions.

Acoustic Stimulation↗
PubMed2005

[Role of the human thalamic parafascicular (CM-Pf) complex in neuronal mechanisms of selective attention].

Responses of 93 single units of the human thalamic CM-Pf complex to relevant and irrelevant verbal (or sensory) stimuli were studied using microelectrode technique in alert diskinetic patients suffering from the tonic forms of spasmodic torticollis during 11 stereotaxic operations. The response patterns of two types units with irregular unitary (A-type) and low-threshold bursting Ca(2+)-dependent (B-type) spike activity were studied. Three main conclusions emerge from the studies: 1) high reactivity of both A- and B-units to presentation of relevant verbal stimuli with differences of their response patterns as determined by the type of constituent elements; 2) close functional connectivity of these neuronal changes with the level of selective attention; 3) at the moment of attention activation, the appearance of transient interneuronal interactions between adjacent A and B cells characterized by the local synchronization and stabilization of rhythmic oscillations. These data point to considerable contribution of the thalamic CM-Pf complex and its neuronal mechanisms into organization of the human selective attention and triggering verbal-related processing during performance of purposive speech-provoked voluntary acts.

Acoustic Stimulation↗
PubMed2004

[Features of the spontaneous unit activity in the human thalamic parafascicular (CM-Pf) complex and its modification in functional cerebral changes].

New data on neural organization of the human thalamic parafascicular (CM-Pf) complex were revealed with microelectrode technique during 11 stereotaxic operations in alert diskinetic patients suffering from the tonic forms of spasmodic torticollis. The data were obtained as follows: the functional heterogeneity in cellular organization of the human CM-Pf thalamic nuclei and the existence of three (A, B and C) different types of neurons in these thalamic nuclei: with the irregular discharges (A-type, 18%); with short (10-20 ms) bursts characterised by unstable rhythmic 2-5 Hz pattern and by the low threshold Ca2+ dependent K+ conductance (B-type, 77%); with long-lasting (0.1-2.0 s) bursts of high-frequency trains and constant interburst intervals (C-type, 5%). The functional cerebral changes after motor test performances were shown to be accompanied by appearance of transient modifications of the background unit activity pattern and by tendency towards an increase of neural activity local synchronisation with some stabilising of oscillatory rhythm of discharging B-type neurons. For the first time, a direct relationship between functional characteristics of the human thalamic CM-Pf units and the motor deviations was found in spasmodic torticollis patients.

Humans↗
PubMed1998

[Changes in the impulse activity of neurons of the human thalamic ventrolateral nucleus during voluntary movement].

Functional differences were revealed in evoked activity of two types (A and B) of units of the human thalamic ventro-lateral nucleus (VL). Collective activities of these polyfunctional neurons were selectively related to triggering and execution phases of movement. Common character of dynamics of the responses seems to be due to similar polyfunctional nature as well as to the functional role of these two complementary elements in the motor signal transmission. The collective activities reflect in the VL the integrative processes related to processing and programming of generalised parameters of motor signals, but unrelated to performance of a concrete motor act.

Humans↗
PubMed1997

[The characteristics of the spontaneous activity of single neurons in the human ventrolateral thalamus during changes in the functional state of the brain].

In the thalamic ventro-lateral nucleus of parkinsonian patients, two main types of convergent cells were shown to exist: 1) units with irregular discharges (A-cells, 74%) and 2) units with bursts of unstable rhythmic discharges (B-cells, 26%). The functional brain changes were accompanied by modifications of A-cells activity into the transient rhythmic burst-like pattern, characterized by two different types of intrinsic structure burst discharges being in some cases similar to the structure of B-cells. A correlation between activities of these units and the type of parkinsonian pathology was revealed.

Action Potentials↗
PubMed1993

Unit activity of nucleus ventralis lateralis of human thalamus during voluntary movements.

The dynamics of change of single VL neurons of human thalamus during voluntary movements was investigated in the course of stereotactic operations on dyskinetic patients. Two basic types of units (A and B cells), reacting to the voluntary movement with different discharge patterns, revealed the common dynamics and a transient time-connectivity of responses correlated with certain phases of the performance of motor acts. It is supposed that these findings reflect the dynamic conjugation of two functionally different cellular subsystems in the human thalamus, which perform collaborative processing and transmitting of information during voluntary movements.

Humans↗
PubMed1990

Unit activity of the human thalamus during voluntary movements.

The quantitative functional analysis of firing patterns has made it possible to classify human VL neurons into two basic types: (1), units with irregular unitary 3-to 20-imp/s activity (A type) and (2) units with short (10-30 ms) rhythmic (3-6 Hz) burst discharges (B type). These two basic types of VL neurons, determined by differences of their discharge patterns and functional properties, are theorized to play a significant role in motor and rhythmic thalamic mechanisms related to parkinsonian tremor. Despite the absence of any direct relationship between rhythmic (3-6 Hz) bursting VL and Rt neurons of the B type and parkinsonian tremor, some indirect relations between them were found.

Afferent Pathways↗
PubMed1990

[A dynamic study of the impulse processes in human cerebral neurons by using the principal-component method].

Evoked activity (EA) of single neurons to verbal (or sensory) stimuli was recorded by microelectrodes in the nucleus reticularis and some other thalamic nuclei of the human brain during stereotaxic operations. An approach is considered which results from the assumptions of the cumulativeness and variability of the EA pattern and is based on the principal component analysis and peristimulus covariation matrices. Application of these methods for estimating unitary responses showed their efficiency for the quantitative analysis of the dynamic structure and interneuronal relations within the EA patterns during the performance of voluntary motor acts.

Brain↗
PubMed1990

[The neuronal reactions of the reticular nucleus of the human thalamus to verbal and sensory stimuli of differing signal strengths].

Responses of 340 single units of the n. Rt of the human thalamus to significant and insignificant verbal and sensory stimuli during the performance of voluntary motor acts recorded by microelectrodes were investigated in dyskinetic patients in the course of 46 stereotaxic operations. Two types of polymodal units with irregular continuous (A-type, "triggered verbal command" units, 183 neurons, 56% reacting) and burst rhythmic (2-5 per s.) discharges (B-type, 139 neurons, 59% reacting) have revealed reactivity to a verbal command with a specialized multicomponent pattern at functionally different stages of purposive motor acts. The analysis of principal components has shown that the extracted components of responses correlated with the functional significance of verbal or sensory signals, especially with voluntary acts of the verbal message triggering, but not with physical, somatotopic or semantic parameters of stimulation. It was suggested that the transient time-connectivity of A and B neurons at the trigger stages of purposive tasks reflected the coexistence in the Rt of two functionally different cellular subsystems participating in the transmission of significant signals during speech-provoked voluntary acts.

Acoustic Stimulation↗
PubMed1990

[The dynamic neuronal interactions in the reticular nucleus of the human thalamus to verbal stimuli of differing signal strengths].

Dynamics of neuronal interaction in 90 ensembles of the RT including units of two types (A, B) recorded by microelectrodes was analyzed during verbal and sensory stimulation and voluntary motor acts in dyskinetic patients in the course of 38 stereotaxic operations. It was shown that high transient interneuronal cooperation in A and B units were selectively related to triggering stages of a purposive act: verbal commands presentation and movement initiation and realization. Specific character of dynamics of interneuronal cooperation determined both by the type of constituent elements and functionally different stages of voluntary acts was found. It is supposed that transient interneuronal cooperation of A and B units reflects dynamic conjugation of two functionally different cellular subsystems in the Rt which are probably connected with verbal-related processing and triggering as well as with movement-related voluntary acts.

Acoustic Stimulation↗
PubMed1987

[Characteristics of neuronal background activity in the reticular nucleus of the thalamus of the human brain].

Background activity of 240 units of n. reticularis thalami (Rt) was investigated by microelectrodes in awake dyskinetic patients during 37 stereotaxic operations. It was shown that Rt can be represented by three types of neurons: units with irregular unitary discharges (A-type, 40%); burst units fired in short 10 divided by 20 ms bursts with unstable rhythmic (2-5 Hz) pattern (B-type, 49%); burst units fired aperiodically in prolonged 0.1 divided by 2 s discharges with constant 80 divided by 150 ms interburst inhibitions (C-type, 11%). Invariant activity-patterns of A-, B- and C-neurons characterized by instability due to functional stimulation were revealed. The unit activity dynamics was described during short-term anaesthesia showing an inhibition of the A-unit activity parallel to stabilization and synchronization of rhythmic bursts of B-neurons. An invariance of the cell type representation of Rt in the dorso-ventral plane was observed, although a number of dynamic activity characteristics of A and B-units increased reliably toward the ventral part of Rt (frequency, variation of rhythm). In addition to the absence of any relationship between rhythmic bursts and parkinsonian tremor, a parameter correlation between them was found. The data show an indirect increase of the firing level and frequency stabilization of the B-unit rhythm parallel to the stage of trembling. The regular burst phenomena in discharges of B and C-neurons are discussed.

Electroencephalography↗