Bilateral Field Advantage of Spatial Attention in Macaque Lateral Prefrontal Cortex.

Allocating visual attention to behaviorally relevant stimuli is easier when distractors are in the opposite visual hemifield relative to when they are in the same hemifield. The neural mechanisms underlying this bilateral field advantage remains unclear. We documented this effect in two macaques performing a covert spatial attention task in two different conditions: when the target and distracter were positioned in different hemifields (across condition), and when they were positioned on the top and bottom quadrants within the same visual hemifield (within condition). The animals' behavioral performance at detecting a change in the attended stimulus was higher in the across relative to the within condition. We recorded the responses of lateral prefrontal cortex (LPFC, area 8A) neurons in one animal. The proportion of LPFC neurons encoding the allocation of attention was larger in the across relative to the within condition. The latter was accompanied by an increase in the ability of single neurons to discriminate the allocation of attention in the across relative to the within condition. Finally, we used linear classifiers to decode the allocation of attention from the activity of neuronal ensembles and found a similar bilateral field advantage in decoding performance in the across relative to the within condition that generalized to different integration time windows and number of neurons used by the classifier. Our finding provides a neural correlate of the bilateral field advantage reported in behavioral studies of attention and suggest a role of the LPFC circuitry in its origin.