Neural Mechanisms Of Different Saccades With Exogenous Cue

We can process information of the target when the target appears,no matter whether our gaze is focused on it or not.However Endogenous attention,exogenous attention and saccadic preparation are related to each other under this situation.In this research we integrate eye tracking and ERP technique by trial to trial paradigm to investigate the neural activities of anti-saccade, pro-saccade and keeping gaze during the instruction stage,the exogenous cue preparation stage as well as the response stage.At the beginning of each trail,a color "+" was presented at the centre of screen to instruct the participant the type of this trial(anti-saccade,pro-saccade or fixation).A randomized flash of the left or the right indicated the related location as a cue.When a target appeared at the flashed location,the participant should generate an anti-saccade or a pro-saccade to the target or fixating the "+" according to the instruction,meanwhile discriminate the shape of the target(round or square).Fifteen undergraduates participated in the experiment.The eye movements data showed that the latency of anti-saccade is longer than that of pro-saccade.The brain activities(ERP) are also different during the instructing stage,exogenous cue preparation stage as well as response stage.During the instructing stage,there is a larger late positive going component in fixation task and the latency is 400ms.The ERPs elicited by exogenous cue in contralateral area of the brain are different in ipsilateral area during the preparation stage.The target was processed as following:(1) detecting the stimulate flashed on the left;(2) saccade preparation;(3) saccade inhibition;(4) paying attention to the left;(5) inhibiting attention's shift.Fixating task evoked a more negative going wave in frontal electrodes during saccadic preparation and saccadic inhibition.Moreover this task evoked a smaller CNV in central electrodes during late period.During the response period,the P1 and N1 in parietal electrodes evoked by contra-lateral target reflected detecting its location and discriminating its shape respectively.In both lateralized parietal electrodes fixating task evoked larger P1 and smaller N1. However anti-saccade task evoked smaller P1 and larger N1 than that of other conditions.In ipsilateral parietal electrodes anti-saccade task evoked larger N1.We observed anti-saccade task and pro-saccade task had an ASDP component preceding the execution of the saccade in the frontal electrodes contra-lateral to the saccade,but fixating task doesn't have the component. These results suggested that fixating task and saccadic task are different in response set.The exogenous cue evokes different processes from the endogenous cue.The neural activities of anti-saccade and pro-saccade have partly common processes.Spatial attention shifts are preceded to the execution of anti-saccade.