Neuronal activity representing visuospatial mnemonic processes associated with target selection in the monkey dorsolateral prefrontal cortex.

To investigate how visuospatial mnemonic and target selection processes are represented in the dorsolateral prefrontal cortex (PFC), we studied neuronal attributes of the dorsolateral PFC while monkeys were performing oculomotor delayed visual search (ODVS) and oculomotor delayed-response (ODR) tasks. In the ODVS task, the subject made a memory-guided saccade to a remembered target location that had been presented along with distractors before a delay period; in the ODR task, the target was presented without any distractors. A total of 252 neurons in the dorsolateral PFC showed directional delay-period activity and were divided into two groups; neurons that showed directional delay-period activity predominantly in the ODVS task (n=112), and those that showed such activity similarly in both the ODVS and ODR tasks (n=140). These neuronal groups shared similar temporal properties (i.e. onset latency, peak time of delay-period activity) and spatial tuning. Our findings suggest that the dorsolateral PFC contains a particular visuospatial memory system for information selected by target selection (selective attention), and this attention-memory system (or 'memory system for special use') appears to be represented in the dorsolateral PFC, in parallel with a more 'general' memory system that is not specifically associated with target selection.