Contextual factors modulate concurrent planning of sequential saccades.

Natural vision typically involves making multiple eye movements to interpret complex visual scenes. Although previous work has shown that individual saccadic end points are modulated by cognitive context, whether and how contextual factors quantitatively influence the planning of sequential saccades is still unclear. We compared performance of subjects in a modified double-step task under different task instructions (FOLLOW vs. REDIRECT; Ray, Schall, & Murthy, 2004) as well as task structure (40% and 100% FOLLOW). The results support the idea of restricted concurrent preparation when the second saccade was part of the sequence as per task demands as opposed to being inadvertently made following an error. Also, increasing the probability of double-target trials in the task (100% vs. 40% FOLLOW) tended to enhance concurrent planning even when the serial order of saccades continued to remain important. Taken together, these data reveal how the concurrent planning of sequential saccades can be contextually regulated by means of task instruction and trial statistics.