Abstract

Based on behavioral evidence, it has been proposed that orientation of visual attention is coupled to oculomotor planning, giving that saccade planning leads to a facilitation of the visual processing of targets at the same visual locus. However, there are evidence of a complete mechanistic independence between an oculomotor planning and attentional orientation. We aimed to examine this dependence during a task that requires visual redirection during a saccade execution. Ten subjects (2 male) performed a dual task (adapted from Deubel and Schneider, 1996) in order to track the location of an attentional focus by discriminating the identity of a peripheral target which is indicated with a central cue, while they have to perform a saccade to a target that is in the same location of the primary task, or to a neighboring site. 25% of the trials were “invalid”, because we presented the discrimination target in the opposite side of the one indicated by the central cue. Each trial begins with the gaze on a central fixation while all possible locations for targets presents a premask. The central fixation is replaced by an arrow which direction and color indicate the side of the discrimination target and the position of the saccade, respectively. The saccade has to be withheld during a variable time (900-1400ms) until a new arrow appears indicating the saccade was to be executed (Go signal). The identification target appears 60ms post Go signal and held for 120 milliseconds, and then replaced by a mask. There were significant differences in saccadic performance between valid and invalid trials. In the valid trials subjects obtained a significant higher percentage of hits to the cued location (40.13%, SD 13.31) versus invalid trials (2.6% , SD 1.53), (p=0.000; F=78.4). Bonferroni test showed a significant difference between valid congruent trials (53.1%, SD 21.0) and invalid congruent trials (21.0%, SD 3.8), p=0.001, F=50.48). These results suggest that, during invalid trials, the absence of the discrimination target in the cued side triggers an attentional reorienting, interfering the execution of the current saccade. A possible explanation for this phenomenon is the existence of shared resources between attentional orienting and oculomotor planning, causing structural interference between these two processes when attention is reoriented.