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S V Afanas'ev

Publications and source records attributed to S V Afanas'ev.

At least 19 recordsLinked to original sources
PubMed2006

[Blocks of neuron correlates of behaviour in the monkey brain prefrontal cortex and striatum].

The dynamics of tonic neuron activity of the putamen and prefrontal cortex of monkey's brain is researched by studying sequential stages of executive behavior program. It is determined that tonic responses in both structures are classified in separate blocks. The blocks are timed to key moments of behavior connected with intermediate goals framed by a common task. As to the structures of the aforesaid blocks of tonic activity in cortex and striatum, they are different in instructive part of the program and similar in executive one. More differential attitude of cortex is revealed to the sequence of executive behavior activity.

Animals↗
PubMed2005

Neuron activity in the monkey striatum of identifies integration sequential actions into functional blocks.

Spike activity in monkey striatum (putamen) neurons was recorded during the performance of a complex multistep operant task. Tonic responses propagating beyond a single action were recorded, along with phasic responses seen within a given action. The tonic type of response was recorded in 132 of 148 cells. Only 11 of these neurons showed exclusively this type of activity. The beginnings and ends of tonic responses were generally associated with key moments in the behavior, corresponding to the triggering and completion of immediate aims during the performance of the behavioral program as a whole. These results provide evidence that the role of the striatum is not limited to controlling single sequentially performed actions, but spreads to the whole structure of a behavioral act.

Action Potentials↗
PubMed2004

Behavior-reactive neuron populations in the monkey neostriatum.

Comparative analysis of neuron activity in the monkey putamen during multistep behavior showed that putamen neurons are active during all the animal's behavioral actions. The difference between the number of active neurons at a given step of the behavior as compared with the preceding step was found to be significantly smaller than the number of neurons reorganizing their activity at this step. Reorganization of neuron activity in the putamen is regarded as a reflection of the efferent code controlling the behavior, while the extent of reorganization is regarded as a measure of the change in this code in association with the organization of a sequential behavioral action. Changes in the numbers of active neurons at different stage of behavior and reorganization of their activity occurred independently of each other. This may be associated with the two afferent systems of the striatum: that ascending from the brainstem and the corticofugal, which carries differential information to the neural network of the striatum from various parts of the cortex.

Action Potentials↗
PubMed2004

The differentiating activity of monkey putamen neurons during performance of alternative spatial selection.

Spike activity was recorded from three zones of the putamen in monkeys trained to bimanual operant activity during performance of an alternative spatial selection task. Neuron responses were analyzed using the following criteria: a) differentiation of the side providing reinforcement (differentiating/non-differentiating responses); b) response duration (tonic/phasic); c) response laterality (contralateral/ipsilateral hemispheres); d) baseline activity frequency. The differentiating activity of cells was found to show the closest correlation with behavioral aspects of the program, particularly the tonic part and, even more so, contralateral tonic responses. It is suggested that differentiating activity, as opposed to non-differentiating activity, is less a reflection of the morphological and neurochemical characteristics of the neural elements of the putamen than of their functional homogeneity in relation to external determinants of behavior.

Action Potentials↗
PubMed2004

Sequential rearrangements of the ensemble activity of putamen neurons in the monkey brain as a correlate of continuous behavior.

Simultaneous recordings were made of the spike activity of groups of 6-7 neurons in the putamen in two monkeys (Macaca nemestrina and Macaca mulatta) during performance of alternative spatial selection. Discriminant analysis was used to evaluate the magnitude of rearrangements in spike activity in groups of neurons during transitions from each step of the behavioral program to the next, along with the degree of differences in reactivity mosaics formed at each step in different versions of task execution. Rearrangements in spike activity were noted at all steps of the program. The dynamics of rearrangements on selection of the right and left feeders were different, leading to the appearance of significant differences in the reactivity mosaics at the decision-taking and reinforcement-receiving steps. The rearrangements preceding voluntary movement of one hand were more marked in the contralateral hemisphere. During performance of movements, the volume of rearrangements could increase, though differences in rearrangements accompanying movements of the right and left hands decreased. On receipt of reinforcement, rearrangements were greater when the animals selected a specified feeder (the left feeder) independently of which hemisphere was recorded.

Action Potentials↗
PubMed2004

[Neuronal activity of the monkey striatum points at the integration of successive actions into functional blocks].

In order to study the role of the striatum in generation of multistage behavior, the spike activity of 148 cells was recorded in the monkey brain putamen. Two kinds of neuron responses were observed. Phasic response involved activity during only one stage of the behavior program, and tonic response involved activity during more than one sequential stage. The tonic responses were recorded in 132 neurons out of 148, 11 neurons responding only as tonic. Other 121 cells show under different conditions both tonic and phasic responses. Beginnings and ends of "tonic" responses as a rule corresponded to the start and completion of the nearest behavioral aim. The obtained data suggest that the neuron activity of striatum is related not only to the control of individual movements but also to the whole structure of behavior.

Animals↗
PubMed2002

[Populations of behavior-reactive neurons in the monkey neostriatum].

Comparative analysis of the unit activity of the monkey putamen during multistage behavior showed that neurons of the putamen are active during all the behavioral actions. It was established that the number of the behavior-related neurons changes considerably less than number of neurons which reorganize their activity at the time. Reorganization of unit activity in the putamen is considered as reflecting the efferent code which controls behavior, and the degree of reorganization--as a measure of change of this code in relation to organization of ongoing behavioral action. It has been discovered that the change in the number of the active neurons at various steps of behavior and reorganization of their activity occurs independently. It may be related to two main afferent systems of striatum: ascending from rhe brain stem, and corticofugal which brings differentiated information to the neuronal net of striatum from various parts of the cortex.

Action Potentials↗
PubMed2002

[Differentiating activity of monkey putamen neurons during performance of the alternative spatial choice].

Single unit activity was recorded in monkeys in three putamen zones learned a bimanual operant activity during performance of the task of alternative spatial choice. The neuronal reactions were specially analyzed by the criteria as follows: a) differentiation of the side of reward (differentiating--non-differentiating reactions); b) character of reaction by duration (tonic-phasic); c) laterality (contra- and ipsilateral reactions as related to hemisphere); d) frequency of background activity. It was shown that differentiating cell activity, especially their tonic part and in still greater degree contra-lateral tonic reactions most closely correlate with behavioral aspects of the program. The assumption that differentiating activity, unlike non-differentiating one, is the reflection of not only morphological and neurochemical characteristic features of nervous elements of putamen but of its functional uniformity in relation to external determinants of behavior, was put forward.

Action Potentials↗
PubMed2002

[Sequential rearrangements of ensemble activity of the putamen neurons of monkeys as a correlate to continuous behavior].

Simultaneous recording of unit activity of 6-8 putamen neurons in two monkeys (M. nemestrina and M. mulatta) during performance of the task of alternative spatial choice, was carried out. The extent of rearrangements of the activity in the groups of neurons with the transition from every step of the behavioral program to the next one and the degree of difference in mosaics of reactivity, forming at every step with a different variants of performance, were evaluated using discriminative analysis. The rearrangements of the impulse activity were recorded in all steps of the program. The dynamics of rearrangements with the choice of right or left feeder was different, which resulted in appearance of significant differences in mosaics of reactivity at the stage of decision making and receiving reward. The rearrangements preceding the task-oriented movement of one hand were more pronounced in the contralateral hemisphere. The volume of rearrangements may increase with the performance of movement but the differences of mosaics formed during the movement of right and left hand are decreasing. At the stage of reception of the reward, the rearrangements were greater in case the animal chose the certain (left) feeder irrespective of the side of recording the unit activity.

Action Potentials↗
PubMed2000

[Clinical course of hepato-gastro-duodenal diseases].

AIM: To characterize clinical course of hepatogastroduodenal diseases (HGDD). MATERIALS AND METHODS: 897 patients with HGDD were examined aged 15 to 82 years. RESULTS: Three groups of patients were recognized: with predominant symptoms of pains in epigastric and hepatic area; with motor-evacuatory disturbances of the stomach and duodenum; with prevailing symptoms of asthenovegetative and depressive disorders. CONCLUSION: Distribution of the patients by type of clinical course provides algorithm of examination and helps to formulate optimal therapeutic policy.

Abdominal Pain↗
PubMed1998

[Study of functional characteristics of brain neurons in behavioral experiment].

The work of the central integrative neurons of the brain is concerned with the total evaluation of the heterogeneous signals and signals of different sensory modality, coming to these neurons via the parallel inputs. Due to the processing of this information central neurons participate in organization of the different acts of animal and in mechanisms of switching from one action to another. Therefore, to define what role the neuron plays in the behavior organization it is necessary to analyse dynamics of unit activities continuously during the all successively performed animal's actions. The traditional methods, such as post- and peristimlus histograms and crosscorrelation are not effective enough for this aim. They are useful for the analysis of the spikes that are situated close to the synchronizing signal only. The application of these methods for the study of unit activity related to extended behavioral program inevitably leads to creation of histograms for each action separately. Such sets of histogram do not reflect the real dynamics of neuronal activity corresponding to the continuum of the behavior. A complex approach is proposed for the study of neuronal correlates of behavior directed towards overcoming of the mentioned difficulties. This approach includes multicomponent behavioral program, recording o spikes in several units in parallel and analysis of unit activities in relative time scale, based on duration of each of the successively performed by the animal action. The nontraditional methods of the processing of spikes sequences are elaborated, such as relative time histograms and methods of the multivariate statistics. The realized on this principles analysis gives a full impression about neuronal activities uninterruptedly, during all stages of performance of the extended behavioral program. The described methods were approved in the experimental study of the functional characteristics of the striatal units in monkeys. The comparable data were obtained on the individual reactions of neurons and dynamics of their activities in group during the performance of behavior program. These data revealed lack of functional specialization of the striatal neurons and different forms of their involvement in the motor and cognitive functions.

Animals↗
PubMed1995

[Neuronal activity of the corpus striatum in monkeys during simultaneously performed actions].

The activities of several striatal units was recorded of parallel in behaving monkeys. The behavioral program includes the differentiation of the conditioned signals with the different levels of complicity. It was shown than the most typical in the relation of the spike activity of the striatal units to the behavior is not the selective involving of individual units into the performance of the certain actions. This activity reflects the animal's behavior as one whole in a way of formation of corresponding mosaics of units activity during the performance of certain elements of the program and in the intervals between them.

Action Potentials↗
PubMed1994

[The reflection of the internal and external behavioral determinants in the neuronal activity of the monkey neostriatum].

The neostriatum neurons were shown to take part in organization of monkey's response to regular situations with the decision-making performed on the basis of existing experience. Other neurons became active in irregular situations involving no previous experience. The latter neurons seem to take part in other form of behaviour organization associated with creation of a new form of response to a new situation.

Animals↗
PubMed1986

[Electrophysiologic analysis of the organization of somatosensory inputs into the thalamus of the cat].

Potentials in the frog thalamus evoked by electrical stimulation of peripheral nerves were studied by the current source-density method. Sinks, considered to be the sites of potentials generations, were found in three regions: in cell-free zone of the ventral thalamus neighbouring the ventrolateral nucleus; in the ventromedial and ventrolateral nuclei; in the caudal part of the dorsal thalamus. The evoked activity of single neurons was registered in the regions of the second and third sinks. After transection of the spinal cord dorsal columns the first sink was absent and the latent periods of two other sinks were prolonged. It is proposed that nuclei of ventral and caudal parts of the dorsal thalamus receive somatic information through the systems connected not only with ventrolateral, but also with dorsal columns of the spinal cord. The direct projections of the primordial nuclei of dorsal columns can participate in the afferentation of the ventral thalamus.

Afferent Pathways↗