The Effects of an NMDA Receptor Antagonist on Delayed Visual Differentiation in Monkeys and Rearrangements of Neuron Spike Activity in the Visual and Prefrontal Areas of the Cortex

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.