Under time pressure, the exogenous modulation of saccade plans is ubiquitous, intricate, and lawful

The choice of where to look next is determined by both exogenous (bottom-up) and endogenous (top-down) factors, but details of their interaction and distinct contributions to target selection have remained elusive. Recent experiments with urgent choice tasks, in which stimuli are evaluated while motor plans are already advancing, have greatly clarified these contributions. Specifically, exogenous modulations associated with stimulus detection act rapidly and briefly (similar to 25 ms) to automatically halt and/or boost ongoing motor plans as per spatial congruence rules. These stereotypical modulations explain, in quantitative detail, characteristic features of many saccadic tasks (e.g. antisaccade, countermanding, saccadic-inhibition, gap, and double-step). Thus, the same low-level visuomotor interactions contribute to diverse oculomotor phenomena traditionally attributed to different neural mechanisms.

Automated summary

This study reveals that the choice of where to look next is influenced by both exogenous and endogenous factors, with their interaction details and unique contributions to target selection becoming clearer. Exogenous modulations associated with stimulus detection quickly and briefly interrupt ongoing motor plans according to spatial congruence rules, explaining characteristic features of various saccadic tasks. These low-level visuomotor interactions contribute to diverse oculomotor phenomena traditionally attributed to different neural mechanisms.