The fate of nonselected activity in saccadic decisions: distinct goal-related and history-related modulation

Abstract

The global effect (GE) traditionally refers to the tendency of effectors (e.g., hand, eyes) to first land in between two nearby stimuli, forming a unimodal distribution. By measuring a shift of this distribution, recent studies used the GE to assess the presence of decision-related inputs on the motor map for eye movements. However, this method cannot distinguish whether one stimulus is inhibited or the other is facilitated and could not detect situations where both stimuli are inhibited or facilitated. Here, we detect deviations in the bimodal distribution of landing positions for remote stimuli and find that this bimodal GE reveals the presence, location, and polarity (facilitation or inhibition) of history-related and goal-related modulation of the nonselected activity (e.g., the distractor activity in correct trials, and the target activity in error trials). We tested, for different interstimulus distances, the effect of the rarity of double-stimulus trials and the difference between performing a discrimination task compared with free choice. Our work shows that the effect of rarity is symmetric and decreases with interstimulus distances, while the effect of goal-directed discrimination is asymmetric — occurring only when the distractor is selected for the saccade — and maintained across interstimulus distances. These results suggest that the former effect changes the response property of the motor map, while the latter specifically facilitates the target location. NEW & NOTEWORTHY Deviations in landing positions for saccades to targets and distractors reveal the presence, location and polarity of history-related or goal-related signals. Goal-directed discrimination appears to facilitate the target location, rather than inhibiting the distractor location, Rare occurrence of a choice appears to indiscriminately increase the neural response for both locations.