Prefrontal delay-period activity is affected by visual cues presented outside the memory field

To examine interactions between primate prefrontal neurons having memory fields, we examined whether primate prefrontal delay-period activity produced by a visual cue presented inside the neuron's memory field is affected by an additional visual cue presented inside or outside the memory field in 39 prefrontal neurons. Delay-period activity was either diminished (43%) or enhanced (16%) when an additional cue was presented at a certain area in the visual field. Since functional interactions among neighboring prefrontal neurons were present, these modulation could be caused by the interactions between neurons having memory fields in different positions.