[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.

Analysis of spontaneous activity patterns of human thalamic ventrolateral neurons and their modifications due to functional brain changes.

In the human thalamic ventralis lateralis nucleus the spontaneous activity of 235 single units during 38 stereotactic operations in locally anaesthetized parkinsonian patients was analysed. Two basic cell types (A and B) were shown to exist in this nucleus: (i) with unitary irregular (2-40/s) discharges characterized by a tendency to spike grouping in the range of 4-6 Hz and 10-30 Hz (A-type, 74%), (ii) with bursting discharges firing in short trains (5-30 ms) characterized by an unstable rhythmic 3-6 Hz pattern similar to a low-threshold Ca2+ intrinsic burst structure of discharges (B-type, 26%). The functional brain changes after a motor tests performance were accompanied by the appearance of two different transient modifications of activity of A-cells pattern into rhythmic burst discharges: (i) in the range of 3-6 Hz, similar to the bursts found for B-cells and recorded mainly in the anterior ventrolateral region in rigid patients, (ii) in the range of 5 +/- 1 Hz, characterized by other interspike interval and recorded in the posterior ventrolateral region in patients with tremor. Modifications during short-term anaesthesia resulted in 10-15 Hz burst discharges that were associated with gradual disappearance of A-cells activity. In contrast to what happens for A-cells, the activity of bursting B-units was characterized by an invariant intrinsic structure of discharges irrespective of the functional brain changes or the forms of parkinsonian pathology. The nature of A- and B-units as well as the mechanisms of transient modifications of their spontaneous activity patterns due to the functional brain changes are discussed.

Analysis of evoked activity patterns of human thalamic ventrolateral neurons during verbally ordered voluntary movements.

In the human thalamic ventralis lateralis nucleus the responses of 184 single units to verbally ordered voluntary movements and some somatosensory stimulations were studied by microelectrode recording technique during 38 stereotactic operations on parkinsonian patients. The tests were carried out on the same previously examined population of neurons classified into two groups, named A- and B-types according to the functional criteria of their intrinsic structure of spontaneous activity patterns. The evaluation of the responses of these units during functionally different phases of a voluntary movement (preparation, initiation, execution, after-effect) by means of the principal component analysis and correlation techniques confirmed the functional differences between A- and B-types of neurons and their polyvalent convergent nature. Four main conclusions emerge from the studies. (1) The differences of the patterns of A- and B-unit responses during the triggering and the execution phases of a voluntary movement indicate the functionally different role of these two cell types in the mechanisms of motor signal transmission. (2) The universal non-specific form of anticipatory A- and B-unit responses during the movement preparation and initiation of various kinds of voluntary movements reflect the integrative "triggering" processes connected with the processing and programming of some generalized parameters of a motor signal and not with the performance of a certain forthcoming motor act. (3) The expressed intensity of these "triggered" non-specific processes in the anterior parts of the ventralis lateralis nucleus indicates their relation not only to the motor but to the cognitive attentional functions forming a verbally ordered voluntary movement. (4) The appearance of the transient cross-correlations between the activities of adjacent A- and B-cells and also the synchronization of their 5 +/- 1 Hz frequency during and/or after motor test performances point to the contribution of these two populations to central mechanisms of the voluntary movement and the parkinsonian tremor. The functional role of two A- and B-cell types is discussed with references to the central mechanisms of verbally ordered voluntary movements and the parkinsonian tremor.

[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 in human thalamic reticularis neurons. II. Activity evoked by significant and non-significant verbal or sensory stimuli.

In the nucleus reticularis thalami (n.Rt.) of 46 dyskinetic patients the responses of 340 single units to significant and non-significant verbal and sound stimuli and ordered voluntary movements were studied. The spontaneous activity of the same neuronal populations previously examined allowed the classification of these neurons into 3 groups, named A, B and C types. Only A and B cells were found to be activated during the verbal command to perform a movement and its realization. The patterns of the responses of these units were studied by means of principal component analysis (PCA) and of correlation techniques during different phases of the command presentation and of the movement. For A cells, two excitatory components A-PC1 and A-PC2 appeared during the command presentation: A-PC1 immediately after its beginning; A-PC2 (trigger component) when an imperative part of the command was pronounced. An excitatory component A-PC3 was connected with the initiation of movement (premotor component); a late excitatory component A-PC4 correlated with movement realization (motor component). For B-units, the inhibitory component B-PC1 corresponded to command presentation; the excitatory component B-PC2 was connected in time with the movement realization. Cross-correlations were studied for simultaneously recorded pairs of A, B and A and B cells. Transitory positive correlations of the activities of two A cells appeared at the time of A-PC1 and, especially of A-PC2 and A-PC3, as well as during the late activation accompanying the movement.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Unit activity in human thalamic reticularis nucleus. I. Spontaneous activity.

Microelectrode recording was carried out in the thalamic reticularis nucleus (Rt) during 51 stereotaxic operations performed in locally anesthetized dyskinetic patients. The spontaneous activity (SA) of 426 units was studied by means of computer processing techniques. Three types of unit (A, B, C) were shown to exist in Rt: with irregular low-frequency (0-10/sec) discharges (A type, 51%); bursting in short trains (10-30 msec) with unstable rhythmic pattern (2-5/sec; B type, 42%); presenting long duration (0.1-2 sec) high frequency bursts and relatively constant interburst silences (80-150 msec; C type, 7%). During short-term anesthesia A unit discharges disappeared; on the contrary the rhythmic bursts of B neurons were synchronized and presented a more stable frequency. The 3 types of cell were present in the whole Rt. However, a number of discharge characteristics (frequency, variation of rhythm) of A and B units changed significantly with the position of the cells in the Rt. No relationship was found between the frequencies of the rhythmic bursts and the parkinsonian tremor. With the use of a multiparametric statistical procedure, a relation was, however, found between the intensity of the peripheral tremor and the stability of the average frequency of the B type rhythmic bursts. The possible origins of rhythmic bursts of B and C neurons are discussed.

[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.