[Significance of local synchronization and oscillatory processes of thalamic neurons in goal-directed human behavior].

The time-frequency characteristics and interneuron interaction in the cell ensembles of non-specific (CM-Pf) and motor (Voi) thalamus were analyzed. Neuronal activity was registered by microelectrode technique during 18 stereotactic neurosurgery operations in spasmodic torticollis patients. The presentation of functionally significant verbal stimuli was accompanied by the emergence of short-term (0.5-1.5 s) local synchronization and stabilization of the oscillatory (3-6 Hz) activity in nearby neurons of nonspecific (CM-Pf) thalamus. These focuses of synchronized oscillatory neuronal activity were correlated with the moment of the greatest concentration of selective attention. Similar phenomenon of short-term synchronization was observed in the motor (Voi) and nonspecific (CM-Pf) thalamus of the human brain during the voluntary movements. Synchronization of neuronal activity occurred at the height of the motor act implementation, correlating with the maximum muscle tension, as well as in aftereffect of the voluntary movement. Overall, the findings suggest an important role of the local oscillations (3-6 Hz) and synchronization ofthalamic neurons in the mechanisms of relevant information transmission during goal-directed human behavior.

[Neuronal mechanisms of motor signal transmission in thalamic Voi nucleus in spasmodic torticollis patients].

Neural mechanisms of motor signal transmission in ventrooral (Voi) nucleus of motor thalamus during the realization-of voluntary and involuntary abnormal (dystonic) movements in patients with spasmodic torticollis were investigated by means of microelectrode technique. The high reactivity of the cellular Voi elements to various functional (mainly motor) tests was proved. Analysis of neuronal activity showed: (1) the difference of neural mechanisms of motor signal transmission in the realization of voluntary movement with and without the involvement of the pathological axial neck muscles, as well as passive and abnormal involuntary dystonic movements; (2) significance of sensory component in the mechanisms of sensorimotor interactions during realization of voluntary and involuntary dystonic head and neck movements, causing the activation of the axial neck muscles; (3) important role of the rhythmic and synchronized neuronal activity in motor signal transmission during the realization of active and passive movements. Participation of Voi nucleus in pathological mechanisms of spasmodic torticollis was shown. The data obtained can be used for identificatiori of Voi thalamic nucleus during stereotactic neurosurgical operations in patients with spasmodic torticollis for selection the optimum destruction (stimulation) target and reduction of postoperative effects.

[Neuronal mechanisms of voluntary and involuntary movements in parafascicular (CM-PF) thalamic complex in spasmodic torticollis patients].

Activity of 144 parafascicular CM-Pf thalamic neurons was studied and recorded by means of microelectrodes during 18 stereotactical neurosurgical operations in spasmodic torticollis patients. High reactivity of two previously classified neurons with single sporadic activity (A-type) and bursts of Ca2(+)-dependent activity (B-type) were found during verbally ordered voluntary movements. There are coordinated reciprocal activation-inhibition A-type and B-type neuronal responses at the stage of verbal command presentation and synergic activation responses on the high of movement and in the aftereffect. Voluntary movement realization was accompanied by short-term local synchronization and stabilization of oscillatory (3-5 Hz) neuronal activity. The neuronal response differences between voluntary movements with and without neck muscle exertion and involuntary pathological movements prove the CM-Pf involvement in the pathology of spasmodic torticollis desease.

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.

[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.

[Features of the spontaneous unit activity in the human thalamic parafascicular (CM-Pf) complex and its modification in functional cerebral changes]. / Osobennosti fonovoi aktivnosti neironov parafastsikuliarnogo kompleksa (CM-Pf) talamusa cheloveka pri izmenenii funktsional'nogo sostoianiia mozga.

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.

Changes in the spike activity of neurons in the ventrolateral nucleus of the thalamus in humans during performance of a voluntary movement.

The responses of neurons in the ventrolateral nucleus (VL) of the thalamus were studied in humans during performance of voluntary motor tests; recordings were made with microelectrodes during stereotaxic operations in patients with Parkinson's disease. Two previously classified types of polyvalent neurons (A, B) were found to show different patterns of responses during the functional stages of carrying out a voluntary movement (preparation, initiation, performance). A and B neurons showed concordant changes in the dynamics of ongoing network activity in the form of linked (activation-inhibition) and synergic (activation) response patterns, correlating with the preparation-trigger and performance phases of movements. It is suggested that the simultaneous activity of both types of neuron, with their common functional nature, reflects integrative processes occurring in the ventrolateral nucleus and associated with programming and processing of general signal parameters but not with the performance of any particular movement. The anterior (Voa nucleus) and posterior (Vop) parts of the ventrolateral nucleus were found to have different roles in organizing voluntary movements, associated with differences in their cellular organization and mechanisms of transmitting motor signals. It is suggested that the concordant changes in the activities of the two types of neurons in these areas seen during the performance of voluntary movements gives the ventrolateral nucleus a key role in the motor control system in humans.

[Changes in the impulse activity of neurons of the human thalamic ventrolateral nucleus during voluntary movement]. / Izmeneniia impul'snoi aktivnosti neironov ventrolateral'nogo iadra talamusa mozga cheloveka pri realizatsii proizvol'nogo dvizheniia.

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.

Features of the spike activity of globus pallidus neurons and pallido-thalamic functional interactions during targeted verbally cued movements in humans.

This paper reports the results of an analysis of evoked spike activity in neurons of the human globus pallidus during performance of a targeted verbally cued movement, along with a comparison with the results of previous experiments on evoked spike activity of neurons in the reticular and ventrolateral thalamic nuclei in an identical test, recorded during stereotaxic surgery with a microelectrode technique in patients with Parkinson's disease. The following observations are reported for the first time: 1) The existence in the outer segment of the human pallidus of neurons with convergent properties, selectively responding with activation to significant "stimulatory" verbal command stimuli initiating the launch and performance of a targeted movement; 2) similarity in the dynamics of concordantly occurring responses of convergent neurons in the integrative centers of the striopallidothalamic circuit in functionally important phases of movement act performance. It is suggested that the similar concordantly developing dynamics of neuronal rearrangements during the performance of a targeted movement act within the structures of this circuit reflects functional interstructural and interneuronal interactions occurring in the striopallidothalamocortical system of the human brain, which is involved in organizing verbally cued targeted forms of activity.

Spontaneous activity of individual neurons in the human ventrolateral thalamus during changes in the functional state of the brain.

Background spike activity of 235 cells of the integrative subcortical motor center, i.e., the ventrolateral nucleus of the thalamus, were analyzed in nonanesthetized human brains during stereotaxic surgery in patients with various forms of Parkinson's disease. Previous data on the existence of two major types of neurons with convergent properties in the ventrolateral nucleus were confirmed. These cell types are: 1) cells with irregular occasional activity, with a tendency for spikes to group into the frequency ranges 5 +/- 1 and 10-30 Hz (type A cells, 74%), and 2) cells with constant rhythmic (3-6 Hz) generation of short volleys of discharges, with an interval structure similar to that of low-threshold Ca(2+)-dependent volley activity (type B, 26%). This is the first report demonstrating that changes in the functional state of the brain (after repeated movement trials, in transient anesthesia) are accompanied by transiently occurring transformations of the initial irregular activity of A cells into a rhythmic, volley-like pattern whose interval structure was in some cases similar to the spike activity of B cells. Differences in the localizations of A and B neurons in the ventrolateral nucleus are described, along with differences in the correlation characteristics of their background spike activity with the pathological features of Parkinson's disease (tremor, rigidity). The nature of the two types of convergent neurons in the ventrolateral nucleus is discussed, and a basis is laid for the importance of the functional factor in understanding the transformation of their background spike activity, due to the properties of cell membranes and intercellular and interstructure interactions in conditions of the living nonanesthetized human brain.

[The characteristics of the spontaneous activity of single neurons in the human ventrolateral thalamus during changes in the functional state of the brain]. / Osobennosti spontannoi aktivnosti odinochnykh neironov ventrolateral'nogo talamusa cheloveka pri izmenenii funktsional'nogo sostoianiia mozga.

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.

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.

[The neuronal reactions of the reticular nucleus of the human thalamus to verbal and sensory stimuli of differing signal strengths]. / Reaktsii neironov retikuliarnogo iadra talamusa mozga cheloveka pri rechevykh i sensornykh vozdeistviiakh razlichnoi signal'noi znachimosti.

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.

[The dynamic neuronal interactions in the reticular nucleus of the human thalamus to verbal stimuli of differing signal strengths]. / Dinamika neironnykh vzaimodeistvii v retikuliarnom iadre talamusa mozga cheloveka pri rechevykh stimulakh raznoi signal'noi znachimosti.

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.

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.

[A dynamic study of the impulse processes in human cerebral neurons by using the principal-component method]. / Issledovanie dinamiki impul'snykh protsessov neironov golovnogo mozga cheloveka s primeneniem metoda glavnykh komponentov.

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.

[Electromyography in patients with spastic torticollis]. / Elektromiografiia u bol'nykh so spasticheskoi krivosheei.

The article describes the results of electromyographic examination of the muscles of the neck in 26 patients with spasmodic torticollis. Electromyography was performed before and after stereotaxic operative interventions on the nucleus of Cajal or in combination with the diencephalic structures. It is shown that electromyographic examination of patients, especially with the use of functional motor and oculomotor tests, widens essentially the possibilities of the diagnosis by facilitating the identification or specification of the predominantly involved group of muscles. The discovery of concurrent oculographic and electromyographic changes in the dominant muscles of the neck during oculomotor tests is evidence of the connection of the system of concurrent movements of the eyes and head with the motor systems participating in the pathology of torticollis. Analysis of the dynamics of electromyographic changes in patients with predominance of the tonic component in the early and late postoperative periods is indicative of gradual increase of positive changes in the motor sphere, which, evidently, is due to the dynamic reorganizations in the previously formed stable pathological system.

[Characteristics of neuronal background activity in the reticular nucleus of the thalamus of the human brain]. / Osobennosti fonovoi aktivnosti neironov retikuliarnogo iadra talamusa mozga cheloveka.

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.