Unilateral Inactivation of Macaque Frontal Eye Field Produces an Impairment of Saccadic Target Selection as Distinct from Attentional Neglect

The frontal eye field (FEF) has been implicated as a possible participant in attentional allocation. Recent studies have found that low-current stimulation of FEF results in enhanced attention and increased visual responses in extrastriate visual area V4. We investigated the necessity of FEF function for allocating attention by unilaterally inactivating FEF in two monkeys and testing the monkeys' ability on a two-alternative forced-choice saccade task. This task was designed to spatially dissociate two processes which we assessed separately: discrimination of a visual cue and generation of a saccade. Following inactivation, we determined the extent of contralesional saccadic deficits, compared to contralesional discrimination deficits, using a choice-based analysis and a reaction time (RT)-based analysis. Overall, we found that unilateral inactivation had an impact on contralesional saccadic performance corresponding to a 61.7-ms overall change in RT and a 34% change in choice probability. On the other hand, we discovered only a 7.0-ms overall change in RT and a 0% change in choice probability with respect to contralesional visual discrimination ability. We conclude that FEF function is much more important for saccadic generation than attentional allocation