Abstract
The pre-motor theory of attention posits that oculomotor regions like the frontal eye field (FEF) are involved in shifts of attention, as well as eye movements. This idea has gained support from behavioral and neuroimaging studies in humans, as well as from microstimulation and recording experiments in monkeys. We reasoned that if the FEF is involved in controlling covert attention shifts, then performance in an attentionally-demanding task should be selectively impaired following FEF inactivation. To test this, we trained monkeys to discriminate the orientation of a briefly-presented target stimulus during fixation. Performance was measured before and after temporary muscimol inactivation of the FEF. In some experiments, the attentional load of the task was manipulated by presenting the discrimination target either alone (low load condition) or with distractors (high load condition). In other experiments, the target was always presented with distractors, and we used valid and invalid spatial precues to manipulate attention. After FEF inactivation, when the discrimination target was presented at the location corresponding to the injection site, performance was impaired in the high attentional load condition, but not in the low load condition. Furthermore, the effectiveness of spatial precues was reduced when the precues were presented in the inactivated field, but not elsewhere. Control experiments show that these effects are not due to simple sensory or motor impairments. Thus, our results indicate that, in addition to its role in controlling eye movements, the FEF plays an important functional role in controlling covert shifts of spatial attention.
Supported by NIH R01-EY014885