Neural correlates of memory updating in the primate prefrontal cortex

Working memory is the ability to temporarily hold and manipulate information during cognitive tasks and is essential for complex behaviors and thinking. Although the primate lateral prefrontal cortex is involved in working memory and the neural representation of short-term memory has been reported, little is known about neuronal activity during memory updating. We trained macaque monkeys to perform an oculomotor version of the n-back task, in which the animals were required to remember the location of serially presented visual stimuli and generate a saccade to the location of the most recent or previous stimulus according to the instructions. We found that many neurons in the lateral prefrontal cortex showed transient activity when the memory of a particular stimulus location was no longer needed, whereas other neurons showed sustained activity when the stimulus location was maintained in memory. Decoding analysis successfully predicted future target selection from neuronal activity, indicating that these neuronal populations contain sufficient information to guide behavior. Furthermore, electrical stimulation applied to recording sites during the task erased specific spatial memories, suggesting that these neurons are causally involved in the retention of short-term memories and their dynamic control.