A. A. Orlov

Collective responses of neostriatal (putamen) neurons during alternative behavior in monkeys

A monkey (Macaca nemestrina) was trained to perform a behavioral program consisting of the selection and execution of a defined sequence of actions according to a visual conditioned signal. Discriminant analysis was used to evaluate the parameters of the collective activity of six simultaneously recorded putamen neurons. The collective activity of the neurons showed significant differences associated with execution by the monkey of left- and right-sided tasks. These differences were seen to be quite consistent in different groups of neurons. Despite the fact that putamen neurons were involved in the performance of nine separately analyzed fragments of the program, differences, were seen in two of these: at the moment of taking the decision relating to the direction of movement, and after its completion when a signal indicating the completed result was presented, independently of whether the animal selected the side for the action correctly or incorrectly. In the case of erroneous decisions, the response mosaic differed from that obtained for correct decisions; however, differences due to previously taken decisions regarding the side of action were preserved. These differences were greater at the point of program completion than at the moment of deciding the direction of movement.

Neuron activity in the monkey striatum during parallel performance of actions

Spike activity was recorded from several neurons in the monkey striatum during the performance of a complex behavioral program including differentiation of conditioned signals of different levels of complexity. The most characteristic feature of spike activity in striatal neurons during behavior was found not to be the selective involvement of particular neurons in carrying out certain actions, but a reflection of behavior as a whole in the form of mosaics of neuron activity corresponding to the moments at which particular actions were performed and during the intervals between them.

Correlates of sequential elements of bimanual behavior in the neuronal activity of the neostriatum in monkeys

Neuron spike activity was recorded in the putamen of monkeys trained to perform bimanual operant behavior consisting of nine separate steps. Neuronal reactions were present at all steps: in 52–62% of cases during movement, and in 27–36% of cases during responses to the trigger and conditioned signals and as the monkeys decided which was the working hand. The proportion of inhibitory responses to the trigger stimulus was 9%, while inhibitory reactions accounted for 68% of reactions during hand movement in response to the conditioned signal, 33% of reactions when this same hand was used to collect food reinforcement, and 33% of reactions during simultaneous movement of both hands. Reactions significantly differentiating between right- and left-sided tasks were seen at all stages of working-hand decision-taking and in reactions to the signal indicating the correctness of the selection, but were not seen for reactions to the conditioned signal or for activity accompanying movements of one of the animals hands. These data provide evidence indicating that each step of the complex operant behavior, individual systems of putamen neuronal reactions were created with qualitatively different integral sensitivity to instantaneous behavior.

Model of the function of the neostriatum and its neuronal activity during behavior in monkeys

Experiments with simultaneous recording of six neostriatum neurons showed that the neurons of this structure are involved in the organization of all stages of behavior. A defined combination of neuronal activity corresponded to each action of the animal. The responses of individual neostriatal neurons were not entirely determined by the action being carried out at a particular moment, but reflected a wider aspect of the overall activity of the animal. These data, along with the established properties of neuronal responses in the neural network model, indicate that the integration of afferent signals in the neostriatum and their distribution to efferent connections is based on network mechanisms of neuronal interaction

Encoding of Conditioned Reflex Activity in Different Directions by Neurons in the Monkey Striatum

Two types of neuron spike activity were detected in the striatum (putamen) of moneys: patterns with low and high activity. Low-activity patterns were no more than twice the level of baseline activity, while high-activity patterns had larger factors. An individual neuron could generate different patterns during different actions. On performance of tasks requiring movement in different directions, the greatest differences in the sets of neurons with high-activity patterns were seen during preparation and onset of the movement in the chosen direction and on completion of the movement. Differences between the sets of neurons with low-activity patterns, conversely, decreased at these behavior stages. They were maximal before presentation of the conditioned signal, when the animal was still unaware of the task, and at the end of the program, when the alternative choice task had been completed. These data provide evidence that the encoding of signals reflecting the involvement of the striatum in solving the alternative choice task occurs by means of multilevel addressed signal encoding. The main role in this is played by changes in the set of neurons generating patterns of different levels of activity.

Responses of the Electrogeneration System of Synodontis (Mochokidae, Siluriformes) to Weak Electric Fields

Electric discharges discovered to date in a novel group of weakly electric fish, the mochokid catfish of the genus Synodontis , are of two types. Discharges of the first type are generated spontaneously with a frequency of several pulses per second and are characterized by a very low amplitude, which does not exceed several hundreds of microvolts [1, 2]. Discharges of the other type occur irregularly and are related predominantly with aggressive behavior of catfish; their amplitudes are considerably greater and may reach several tens of millivolts [3, 4].

The Relationship between Prefrontal Cortex Neuron Activity in the Two Hemispheres on Performance of a Choice Task in a Two-Ring Maze

Neuron activity in two symmetrical areas of the prefrontal cortex in the left and right hemispheres of the rat brain (55 and 47 neurons, respectively) was recorded as the animals performed a behavioral choice task in a two-ring maze. Experiments were performed in two sets of conditions – i) working with a conditioned signal, when excursions to the side indicated by the signal were reinforced, and ii) without a signal, when any excursion was reinforced. The levels of involvement of a neuron in different steps of the behavioral program were evaluated in terms of the level of differential activity, i.e., differences in neuron activity in right- and left-sided performances. In conditions in which the animal took the decision without orienting itself to external signals (in two behavioral situations: working without signals and erroneous performance of the program), there was a predominance of differential activity in the left hemisphere. In correct performances of the program, activity dominated in the right hemisphere. This appears to be evidence of a consistent dynamic in the interaction between the hemispheres depending on external and internal conditions and the special role of the right hemisphere in learning mechanisms and inclusion of the external determinant in the adaptive response system.

A Two-Ring Maze for Studies of the Behavior of Laboratory Animals

The behavior of rats was studied in a two-ring maze in which the animal could make its own choice of one of two trajectories of the same length, independently returning to the start point. All maze sectors – starting chamber, signal sector, arm, and feeding sector – were separated by one-way doors. The time structure of passage through the maze sectors reflected both the level of the animal’s motivation and fully defined aspects of behavior, i.e., attention, short-term memory, and long-term memory, as well as the cognitive aspect, i.e., taking movement trajectory decisions on the basis of the conditioned signal presented, and the emotional aspect, i.e., assessment of the result of the action. Analysis of the time parameters of the activity allowed changes in various behavioral components to be evaluated in relation to treatment applied to the animals and ongoing status. We suggest that this behavioral model will be useful in different types of neuropharmacological, electrophysiological, and behavioral experiments.

Combinations of active striatal neurons connected selectively with certain behavioral actions of the monkey Macaca mulatta

At present there is widely spread concept of populational coding of information by brain neurons; it is based first of all on results of comparison of neuronal activity with parameters of the used stimulus. Relation between the neuronal activity coding and the observed behavioral actions has been practically not studied. In the present work, neuronal impulse activity has been studied in groups of 6 neurons recorded in parallel. Distribution of frequencies of the presence of cases of excitation of one or several cells has been established to differ statistically significantly from the theoretical distribution of the same values; this indicates that under real conditions, the appearance of individual combinations of active neurons is not random, but is connected to a certain degree with conditions of experiment. The selective combinations of neuronal activity have been revealed to be different at stages of program. This indicates that organization of different behavioral actions is associated with activities of certain combinations of neurons.

Reorganization of Composition of Striatal Neurons Correlating with Behavior in the Monkey Macaca nemestrina

The available experimental data do not provide a sufficiently complete picture of the neuronal activity connected with some action of the animal, as they have been obtained under different experimental protocols and as a result of study of different cells. The present work was aimed at studying activity of the same neuron group at different moments of animals behavior. A monkey (Macaca nemestrina) was taught to perform a behavioral program consisting of several functional heterogeneous actions. The impulsive activity of striatal neurons was recorded in the central region of putamen with coordinates A 16.5, L7, and H 8–10 [18]. The activity of each neuron was recorded during 13 consecutive stages of the same behavioral task. As a whole, in 59 putamen neurons, 767 fragments of neuronal activity were studied. It was shown that the same neurons could be involved at different behavioral stages when the animal performed different actions. At individual stages, the number of neurons common with other behavioral stages reached 70–80% of all reactive cells at the stage. The number of the neurons common within the rest of 12 stages was determined for every program stage. The number of such common neurons established in the experiment was in 142 out of 156 cases higher than their number that could be expected on the basis of statistical relations. The data obtained indicate that the reorganization in composition of behavior-reactive cells at every behavioral stage occurs mainly by using the same neurons but not only the neurons that are specialized for the given action. The polymodality of individual striatal neurons is unlikely to be connected with that they have several functions, but results from that the same neuron can be a constituent of neuronal mosaics of different configurations corresponding to different behavioral moments.