Abstract

It has been proposed that orientation of visual attention is coupled to oculomotor planning, giving that saccade planning leads to facilitation of the visual processing of targets at the same visual locus. However, there is evidence of complete mechanistic independence between both processes. If visual attention depends on oculomotor planning, we expect to find interference between both processes when each one is directed to a different locus. This interference would manifest itself through a drop of saccadic behavior or a different time course of electrophysiological markers. Nine subjects (4 male) performed the dual task in order to track the location of an attentional focus by discriminating the identity of a peripheral target (OD), while they have to perform a saccade to a target that is in the same location of the primary task (congruent trial), or to a neighboring site (incongruent, INC1 and INC3). Each trial begins with the gaze on a central fixation which is replaced by an arrow whose direction and color indicate the side of the OD and the position of the saccade, respectively. The saccade was withheld during a variable time until a Go signal. We found that target discrimination was significantly higher for incongruent trials compared to but there was no difference between congruent and INC1. During post CUE period, oscillatory activity (Beta band) showed a spectral power decrease at posterior electrodes, contralateral to the cued target, compared to ipsilateral, both in congruent and INC1. Such lateralization of beta had an earlier time course in INC1 than congruent trials. During the Go period, beta band showed clear lateralization of spectral power in congruent trials and was not present in incongruent trials. Our results suggest that there is no interference, without a time cost for the direction of saccade and visual attention to different sites. However, the different time course of beta band activity during post CUE period may reflect an anticipatory process for sensory-motor integration, which avoids a time cost in the post GO period. The experiment showed no evidence of interdependence between visual attention orienting and oculomotor planning. The results suggest a dissociation between the two processes and no interference between them.