Reliability of macaque frontal eye field neurons signaling saccade targetsduring visual search

Although many studies have explored the neural correlates of visual attenti on and selection, few have examined the reliability with which neurons repr esent relevant information. We monitored activity in the frontal eye field (FEF) of monkeys trained to make a saccade to a target defined by the conju nction of color and shape or to a target defined by color differences. The difficulty of conjunction search was manipulated by varying the number of d istractors, and the difficulty of feature search was manipulated by varying the similarity in color between target and distractors. The reliability of individual neurons in signaling the target location in correct trials was determined using a neuron-anti-neuron approach within a winner-take-all arc hitecture. On average, approximately seven trials of the activity of single neurons were sufficient to match near-perfect behavioral performance in th e easiest search, and similar to 14 trials were sufficient in the most diff icult search. We also determined how many neurons recorded separately need to be evaluated within a trial to match behavioral performance. Results wer e quantitatively similar to those of the single neuron analysis. We also fo und that signal reliability in the FEF did not change with task demands, an d overall, behavioral accuracy across the search tasks was approximated whe n only six trials or neurons were combined. Furthermore, whether combining trials or neurons, the increase in time of target discrimination correspond ed to the increase in mean saccade latency across visual search difficulty levels. Finally, the variance of spike counts in the FEF increased as a fun ction of the mean spike count, and the parameters of this relationship did not change with attentional selection.