Representation of the temporal order of visual objects in the primate lateral prefrontal cortex.

Recollecting a past episode involves remembering the temporal order of events. We studied cellular activity in the lateral prefrontal cortex (PFC) of two monkeys that were required to remember the temporal order in which visual objects appeared and to reach for each object in the same order after a delay. Here, we report the cellular activity in the lateral PFC, focusing on the delay period. We found that 43% of the delay-period activity was selective for the sequence in which the visual objects were presented during the cue period. While the majority of cellular activity was selective for multiple sequences, some cells (31%) were selective for only one of six sequences. Our findings show that PFC cells are involved in holding temporal order information when that information is necessary for planning forthcoming motor behavior.