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The effects of perfusion of field 17 with the glutamate receptor antagonist 2-amino-5-phosphonovaleric acid (APV) on the characteristics of visual recognition and short-term memory were studied, along with the effects of APV on the responses of neurons in the visual and prefrontal areas of the cortex in rhesus macaques. In the test for delayed visual differentiation of stimuli of different colors, behavioral data were recorded simultaneously with multichannel recordings of the spike activity of single cells in cortical field 17 (directly within the microdialysis zone) and field 8. Multifactor dispersion analysis (ANOVA) showed that APV significantly worsened the behavioral characteristics in monkeys, with significant reductions in the duration of short-term storage of information (by factors of 2-4) and significant increases in the motor response times. These changes in cognitive characteristics induced by APV were accompanied by changes in the spike activity of neurons in the visual and prefrontal areas of the cortex during the sensory analysis and delay stages; changes in spike activity consisted of significant desynchronization. These results show that cognitive dysfunctions consisting of worsening of short-term remembering of information and increases in the duration of motor responses during exposure to APV may be caused by desynchronization of neuron activity in various areas of the cortex, these being involved in neuron ensembles responsible for the mechanisms of short-term memory, in which glutamatergic structures play an important role.

A delayed visual differentiation task using stimuli of different colors was used in rhesus macaques to study the characteristics of visual recognition, short-term memory, and the responses of neurons recorded simultaneously in the visual and prefrontal areas of the cortex, along with their relationships with the site of intracortical (fields 17 or 46) perfusion of the glutamate receptor antagonist 2-amino-5-phosphonovaleric acid (APV). The behavioral characteristics and spike activity of individual cells in cortical fields 17 and 46 were recorded before and after perfusion with APV and after washing away of traces of APV. Multifactor dispersion analysis showed that the effect of APV in monkeys consisted of decreases in the probability of correct responses, leading to a decrease (two-fold) in the duration of short-term storage of information and a significant increase in the motor reaction time. The probability of correct solutions depended on the site of APV perfusion in the cortex, while the motor response time was independent of the perfusion site. Perfusion of field 46 with APV, unlike perfusion of field 17, altered the spike activity only of neurons in the prefrontal cortex, while no significant changes were seen in the neuron activity of the visual cortex. The actions of APV were accompanied by significant desynchronization of neuron activity in these two areas as compared with the level of synchronization in normal conditions; after traces of APV were washed away, the extent of desynchronization decreased. The neurophysiological correlates of cognitive dysfunctions associated with degradation of visual recognition and short-term memory due to modification of glutamatergic structures by blockade of NMDA receptors are discussed.

A multi-factor variance analysis revealed that the 2-amino-5-phosphonovalerian acid (APV) effect was manifested in monkeys by a decrease in the number of correct responses entailing a two-fold shortening of the short-term information storage, as well as by an augmentation of the motor responses' time. The correct responses' probability depended on the APV diffusion localisation in the cortex whereas the motor responses' time did not depend on it. The APV effect was accompanied by a desynchronisation of the unit activity in fields 46 and 17. Neurophysiological correlates of cognitive functions, are discussed.

With the aid of a multichannel leads the unit activity was recorded in the 17th and 8th cortical fields along with registering behavioural data in Rhesus monkeys. Multi-factor variance analysis revealed that the 2-amino-5-phospho-valeric acid (APV) effect involved a significant worsening of the monkeys' behavioural characteristics: duration of the short-term memory shortened (2-4-fold), motor reactions' time increased, and the changes of cognitive characteristics were always followed by significant rearrangements of the unit activity in the above areas. The data obtained suggest that these cognitive dysfunctions are due to a desynchronisation of unit activity in different areas of the cortex including the neuronal assemblies maintaining the short-term memory mechanisms associated with the glutamatergic structures.

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.

During a 2.5-min. hypoxia in monkeys, a rearrangement of the unit activity occurred in the visual and prefrontal cortex. Following this, the motor response in delayed visual spatial reaction tack did not restore during several hours. The rearrangement involved appearing of sequential phases of hyperactivation and inhibition. Duration of the posthypoxic inhibition and ratio of posthypoxic hyperactivation frequencies to the background one were significantly greater in the prefrontal cortex than in the visual one.

In behavioral experiments on monkeys tested for a delayed visual differentiation of different colours stimuli, neuronal pools were recorded simultaneously in the visual, prefrontal and inferotemporal cortex. Wrong motor responses were always followed by considerable readjustments of the unit activity patterns whereas in right decisions a synchronisation and a cross-correlation occurred between neuronal pools. Possible mechanisms of the decision making and the reasons for the desynchronisation in wrong responses, are discussed.

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.

Characteristics of visual recognition were impaired by amysil influence in monkeys. This was accompanied by a considerable activation of unit activity in the prefrontal cortex. Amysil induced a considerable drop in the cross-correlation coefficients between simultaneous responses of neuronal populations in prefrontal and inferotemporal cortex.

Unit activity was studied in the visual cortex prior to and after amyzyl administration in monkeys trained for delayed visual differentiation of different colour stimuli. The data obtained suggests that the cholinergic mechanisms of the visual cortex are involved in the visual recognition and seem to play different functional roles at different stages of the behaviour.

A normal differentiation between black and white visual stimuli lesioned by phthoracisine can be restored by oxymetacyl administration (3 mg/kg) in monkeys. The colour differentiation is restored after the dose 4 mg/kg. The data obtained suggest correcting effect of oxymetacyl.