Prefrontal unit activity during delayed-response and delayed-alternation performances

In order to examine whether or not the single unit activity of the dorsolateral prefrontal cortex of the rhesus monkey activated during delayed-response task is involved in a delayed-alternation task, the same prefrontal single unit activities were recorded extracellularly using tungsten electrodes while the monkey was performing the two tasks alternatively. Visual signals were given to two different locations (left and right) as visual cues and response cues. A total of 95 units were recorded. Two-thirds of them were activated during visual and response cue phases and were regarded as the visuokinetic units as defined in a previous paper (KUBOTA et al., 1974). Visuokinetic units with no different discharge rate between left and right trials of delayed-response did not show a difference in delayed-alternation. Visuokinetic units with a differential rate in delayed-response trials did not necessarily show a difference in delayed-alternation. Visuokinetic units with no spontaneous activity in the intertrial interval time were considered as the E unit activity of delayed-alternation in a previous paper (KUBOTA and NIKI, 1971). Remaining one-third of units were activated or depressed during visual cues or during response cues and their activities were not different from each other between two tasks. No differential activity was found which could be correlated to the alternative choice of the reward in delayed-alternation. Discussions were made on possible mnemonic functions relevant to previous studies.