The influence of an effective antioxidant, oxymethacil, was studied in a model of the disruption of visual recognition induced by the antidepressant fluoracyzine. The normal discrimination of black and white visual stimuli in monkeys is restored with the systemic administration of oxymethacil in a dose of 3 mg/kg following disruption brought about by the effect of fluoracyzine. The discrimination of colored visual stimuli, as in the norm, is restored following the systemic administration of oxymethacil in a dose of 4 mg/kg. The results obtained attest to the corrective properties of oxymethacil.

Animals↗

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Characteristics of excitation and inhibition of the receptive fields of the retina and lateral geniculate body.

The process of excitation and inhibition in the receptive fields (RF) of the ganglion cells and lateral geniculate body (LGB) of the cat were examined. The extent of the dependence of the magnitude of excitation and inhibition in RF on stimulus intensity was determined. This dependence is a power function with power indices of 0.15--0.20 (LGB) and 0.3--0.5 (retina) for excitation and 0.2--0.3 (LGB) and 0.5--0.6 (retina) for inhibition.

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PubMedDate not supplied

Processes of visual recognition in monkeys and their neuronal correlates in the visual cortex: the influence of a blocker of M-cholinoreceptors.

The activity of individual neurons of the visual cortex was recorded simultaneously in behavioral experiments on monkeys before and after the systemic administration of a blocker of M-cholinoreceptors, amizil (0.8-1.0 mg/kg). The animals were trained to delayed visual differentiation of stimuli of various colors. After the administration of amizil, the characteristics of recognition deteriorated substantially: the duration of the storage of information in short-term memory sharply declined, while the time of the motoric reaction increased. The deterioration of these characteristics was accompanied by inhibition of the activity of the neurons of the visual cortex, inhibition which depended on the stage of recognition, and which intensified when there was an increase in the delay interval. The results obtained suggest that cholinergic mechanisms of the visual cortex are included in visual recognition, and apparently play various functional roles at various stages of behavior.

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PubMedDate not supplied

Dynamics of the impulse activity of neurons of the neocortex of monkeys in a visual recognition task after brief oxygen deprivation.

A model of brief oxygen supply disruption was created in monkeys trained to a delayed visual spatial choice. A substantial reorganization of the impulse activity of neurons of the visual and prefrontal cerebral cortex, accompanied by disturbances in behavioral reactions, was observed during brief hypoxia (2.5 min); the motor reaction was not restored for several hours in the monkeys during a delayed visual spatial choice. The reorganization of the activity consisted in the appearance of successive phases of hyperactivation and inhibition. The frequency of the impulse activity in the phase of hyperactivation was higher in prefrontal cortex neurons. Successive phases of inhibition and hyperactivation were also identified in the posthypoxic period of restoration in the structure of the activity. The duration of the posthypoxic inhibition and the ratio of the frequencies of posthypoxic hyperactivation to the baseline frequency in the reactions of prefrontal cortex neurons was substantially greater than in the neurons of the visual cortex.

Acoustic Stimulation↗

PubMedDate not supplied

Neurophysiological correlates of improvements in cognitive characteristics in monkeys during modification of NMDA-ergic structures of the prefrontal cortex.

The effects of modification of NMDA-ergic structures by microdialysis perfusion in the prefrontal cortex (field 8) with NMDA glutamate (2 mM) on visual recognition and short-term memory (STM) were studied in rhesus macaques, using methods based on the deferred differentiation of stimuli of different colors. Impulse activity of neurons in the prefrontal and visual cortex was measured during these experiments, both before and after administration of NMDA. NMDA increased (2-fold) the duration of short-term retention of information and significantly reduced the latent period of the motor response at all delay periods, and also produced significant changes in neuron activity in the prefrontal cortex: depending on the stage of behavior, activity decreased in 60-75% of neurons and increased in 8-26%. NMDA produced significant increases in the cross-correlation coefficients between the responses of neurons in the visual and prefrontal cortex. The results showed that glutaminergic structures in the prefrontal cortex are involved in processes of visual recognition and STM in monkeys. The effect of NMDA, which synchronized cortical neuronal processes, improved the short-term understanding of visual information.

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PubMedDate not supplied

Neurophysiologic correlates of the decision-making processes in the cerebral cortex of monkeys during visual recognition.

The impulse activity of groups of neurons of the visual, prefrontal, and inferotemporal cortex was recorded simultaneously in behavioral experiments on monkeys solving a problem of delayed visual differentiation of variously colored stimuli. The neurophysiological correlates of the decision-making processes were studied. Erroneous motoric reactions were accompanied in all monkeys by significant reorganizations of the patterns of impulse activity of the neurons. In the case of correct solutions of the monkeys, synchronization in time and cross-correlation which was significant in magnitude between the activity of the groups of neurons were observed. Incorrect solutions were accompanied by desynchronization and by a decrease in cross-correlation between the activity of these groups of neurons. Possible decision-making mechanisms of the causes of the desynchronization of the informational processes during erroneous reactions are discussed.

Acoustic Stimulation↗

PubMedDate not supplied

Influence of an antioxidant on the impulse activity of neurons of the prefrontal and inferotemporal cortex during visual recognition in monkeys.

The impulse activity of individual neurons of the prefrontal and inferotemporal cortex was recorded during the performance of a task of delayed visual differentiation of stimuli of various colors in monkeys before and after the systemic administration of the antioxidant, oxymethacil (4-5 mg/kg). The improvement in cognitive characteristics induced by oxymethacil was accompanied by changes in the activity of neurons of the prefrontal cortex in which activation dependant upon the stage of recognition and intensifying during an increase in the duration of the delay predominated. Inhibition of activity predominated during recognition without delay in these neurons; by contrast, activation predominated in neurons of the inferotemporal cortex under these conditions. During delayed differentiation, the activity of these neurons under the influence of oxymethacil changed principally in the same way as in neurons of the prefrontal cortex: activation predominated in the majority of the stages of recognition. Oxymethacil induced a substantial increase in the coefficients of cross correlation between simultaneous respondent reactions of groups of neurons in these different areas of the cortex. The results obtained attest to the contribution of neuronal structures of the prefrontal and inferotemporal cortex to the improvement of cognitive characteristics of monkeys in the presence of the effect of oxymethacil, and to the increase in synchronization of informational processes in these regions of the cortex.

Animals↗

PubMedDate not supplied

Participation of cholinergic structures of the prefrontal and inferotemporal cortex in the processes of visual recognition in monkeys.

Monkeys performed a task of delayed visual differentiation of differently colored stimuli in behavioral experiments. The impulse activity of individual neurons of the prefrontal and inferotemporal cortex before and after the systemic administration of a blocker of M-cholinoreceptors, amyzil (0.8-1.0 mg/kg), was recorded simultaneously. Deterioration of the characteristics of recognition induced by amyzil was accompanied mainly by a significant increase in the activity of neurons of the prefrontal cortex which was dependant on the stage of recognition, and intensified with an increase in the delay interval. The impulse activity of the neurons of the inferotemporal cortex varied in the process without a regular pattern: at some stages of recognition it increased, at others it was inhibited. Amyzil induced a substantial decrease in the coefficients of cross correlation between the simultaneous respondent reactions of groups of neurons of the prefrontal and inferotemporal cortex. The results obtained point to the fact that the cholinergic structures of the inferotemporal and prefrontal cortex participate, at various stages of visual recognition in monkeys, in the formation of the dynamic functional systems which make their specific contribution to informational processes.

Animals↗

PubMedDate not supplied

An antioxidant-induced improvement in the cognitive characteristics of monkeys: neurophysiological correlates in the visual cortex.

After the injection of the antioxidant, oxymethacil (4-5 micrograms/kg), in an investigation in monkeys of the processes of delayed visual recognition, their cognitive characteristics were significantly improved.: the duration of the short-term storage of information increased (by a factor of 2-3) and the time of the motor reaction decreased. The improvement of the cognitive characteristics was accompanied by changes in the neuronal activity in the visual cortex at all stages of recognition. The activity of the majority of the neurons increased in the case of discrimination without delay, it decreased significantly in the case of delayed discrimination. The administration of oxymethacil induced an increase in the auto- and cross-correlation coefficients in the respondent reactions of the recorded groups of neurons. The results obtained suggest that oxymethacil possesses nootropic properties, and the participation of the visual cortex of monkeys in the realization of these properties for the improvement of cognitive characteristics.

Acoustic Stimulation↗

PubMedDate not supplied

Short-term memory processes in delayed visual differentiation in rhesus macaques after bilateral removal of field 7 of the parietal cortex.

Monkeys (Macaca mulatta) with preliminary removal of field 7 of the lower parietal cortex and previously trained to differentiate images differing in shape, color, size, orientation, and spatial relationships were used to study the processes involved in short-term storage of different types of information required for a delayed (by 0-8 sec) visual differentiation task and the effects on these processes of the antioxidant Oxymetacil. Significant differences were found in comparison with intact animals. Removal of field 7 sharply worsened short-term storage processes during visual differentiation of different types of images, including those differing in terms of properties such as color, geometrical shape, and the spatial relationships between image elements. There were significant reductions in the level of correct responses for all delay periods with significant increases in the motor reaction time, indicating a sharp reduction in the duration of short-term information storage, which suggests that the monkeys' short-term memory mechanisms were disrupted. Oxymetacil had a correcting effect only in relation to stimuli differing in terms of color and shape, but had no effect at all on the short-term storage of spatial information. It is suggested that these data suggest that field 7 has at least two functions. These are, firstly, a role in processes underlying the evaluation, differentiation, and storage of spatial information depending on visual-vestibular interactions, and secondly, a role in the mechanisms underlying the attention system, which is disrupted by removal of field 7 and restored by treatment with the antioxidant when there is no need to differentiate spatial information, a process which depends on assessment of the body image and egocentric orientation based on visual-vestibular interactions.

Animals↗

PubMedDate not supplied

Specific characteristics of cholinergic mechanisms of short-term memory in monkeys for different types of visual information: the effects of amizil.

Experiments on rhesus macaques were used to study the relationship between the characteristics of delayed visual differentiation and stimulus properties in conditions of pharmacological treatment with the m-cholinoreceptor blocker amizil, with the aim of identifying how modification of cholinergic structures affects different types of information. Disturbances to short-term memory for all stimuli consisted of reductions in the duration of retention and increases in motor reaction times, but occurred at different doses of the blocker: amizil at a dose of 0.3 mg/kg significantly decreased the retention duration for information relating to spatial relationships. Delayed discrimination of shape, contrast, and size worsened after treatment with amizil at a dose of 0.45-0.50 mg/kg, while decreases in the duration of short-term storage of information relating to color started after amizil doses of 0.6-0.8 mg/kg. It is suggested that the short-term memory system includes a set of neurophysiological mechanisms in which the cholinergic structures are organized differently and whose specific properties result in differences in the characteristics of short-term storage of different types of visual information.

Animals↗

PubMedDate not supplied

Effect of NMDA on the activity of cortical glutaminergic structures in delayed visual differentiation in monkeys.

The effect of intracortical perfusion with the glutamate agonist NMDA on visual recognition and short-term memory, as well as an on the responses of visual cortex neurons, were studied in rhesus macaques. A microdialysis technique was used in combination with multichannel microelectrode recording of single cortical cells in the immediate vicinity of the dialysis tube in a behavioral experiment in which the monkey had to solve a task involving delayed visual differentiation of stimuli of different colors. NMDA altered the characteristics of recognition in monkeys. The duration of information storage in short-term memory was increased significantly (2-4-fold), and there was a significant reduction in the motor response time for all delay periods. These changes were accompanied by a significant rearrangement of neuron activity in the visual cortex at all stages of the behavioral task. At different stages of the task, 70-85% of the neurons showed 2-5-fold increases in activity, while 6-20% showed reductions in activity. These results demonstrate an involvement of visual cortex glutaminergic structures in the process of visual recognition and short-term memory, as well as a nootropic effect obtained by intracortical administration of NMDA.

Action Potentials↗

PubMedDate not supplied

Synchronization processes in the mechanisms of short-term memory in monkeys: the involvement of cholinergic and glutaminergic cortical structures.

Behavioral experiments were carried out in which monkeys had to solve a task involving delayed visual discrimination, and activity was simultaneously recorded from several neurons of the visual, prefrontal, and lower temporal regions of the cortex before and after modification of cholinergic (by systemic infusion of the M-cholinoceptor blocker amizil) and glutaminergic (by intracortical perfusion with glutaminergic agonists and antagonists, i.e., NMDA, aminophosphonovalerianic acid (APV) and aminophosphonobutyric acid (APB)) systems. Amizil and APV reduced the duration of short-term information retention and increased the delay before the motor response was made. Worsening of these parameters was accompanied by a significant level of desynchronization of activity in the groups of neurons studied. NMDA and APB improved short-term memory and increased neuron synchronization. The role of synchronization of information processes in the mechanisms of short-term memory and the involvement of the cholinergic and glutaminergic systems are discussed.

Aminobutyrates↗