Lateralized EEG markers of attention preceding and following shifts in eye position

Attention and working memory are largely organized in a contralateral fashion in cortex. However, it remains unclear how eye movements impact this organization. Here we examined how subjects allocated attention prior to moving their eyes to a new fixation target and how attention was impacted after the eye movement is executed. In Experiment 1, subjects initially fixated a central cross and were cued with a left or right arrow for 500 ms. After a 1000-ms delay period, a cue instructed them to either maintain or make a saccade to one of two lateral fixation crosses. Prior to the eye movement, we observed a sustained negativity in the hemisphere that was contralateral to the intended saccade target position, suggesting an attentional shift to the saccade target before the eye movement. After the eye movement, we observed a large (>4 microvolts) sustained positive wave that was contralateral to the saccade target. This sustained contralateral positivity persisted even after the eyes had now foveated the new lateral fixation point, suggesting a lingering retinotopic attentional code for the saccade target. In Experiment 2, we extended our findings by adding a working memory task with three laterally-presented color squares on each hemifield. Following the encoding of lateralized color squares, participants were then cued to move their eyes according to which block they were in, before a working memory test for the color squares appeared at the end of each trial. We observed an increase in the pre-movement contralateral negativity induced by the working memory load. However, we still observed the large sustained positive wave that was contralateral to the saccade target. Together these results reveal distinct neural markers of attentional shifts preceding and following eye position shifts.