Neural Correlates of Task-related Refixation Behaviour

Abstract

Information uptake during scene viewing under free viewing conditions is crucially determined by the scanning plan. This plan is determined both by top-down and bottom-up factors. To capture top-down factors affecting saccade planning, we compared EEG between first fixations and refixations on items varying in task-relevance. First fixations and refixations impose different working memory costs because first fixations involve encoding of new items whereas refixations involve rehearsal of existing items in working memory. These memory requirements also differ with the task-relevance of the item being encoded. Together, these two factors of task-relevance and memory processes related to refixation behavior would affect saccade planning. In a visual task involving search and memorization of multiple targets, we compared saccade-related potentials (SRPs) between first fixations and refixations for task-relevant (target) and task-irrelevant (distractor) items. We assessed the interval preceding a saccade away from the fixation of interest. Studying this presaccadic interval revealed how mechanisms related to saccade preparation are affected by task-relevance and refixation behavior. We found higher SRP amplitudes for first fixations than refixations over the occipital region for task-relevant items only. Our findings indicate that saccade planning is modulated by both task-relevance of an item and working memory load.