A Distinct Contribution of the Frontal Eye Field to the Visual Representation of Saccadic Targets

The responses of neurons within posterior visual cortex are enhanced when response field (RF) stimuli are targeted with saccadic eye movements. Although the motor-related activity within oculomotor structures seems a likely source of the enhancement, the origin of the modulation is unknown. We tested the role of the frontal eye field (FEF) in driving presaccadic modulation in area V4 by inactivating FEF neurons at retinotopically corresponding sites within the macaque monkey (Macaca mulatta) brain. As previously observed, FEF inactivation produced profound, and spatially specific, deficits in memory-guided saccades, and increased the latency, scatter, and duration of visually guided saccades. Despite the clear behavioral deficits, we found that rather than being eliminated or reduced by FEF inactivation, presaccadic enhancement of V4 activity was increased. FEF inactivation nonetheless diminished the stimulus discriminability of V4 visual responses both during fixation and in the presaccadic period. Thus, without input from the FEF, V4 neurons signaled more about the direction of saccades and less about the features of the saccadic target. In addition, FEF inactivation significantly increased the suppressive effects of non-RF stimuli on V4 activity. These results reveal multiple sources of presaccadic modulation in V4 and suggest that the FEF contributes uniquely to the presaccadic specification of visual target features.