Abstract
Several studies have shown that the execution of goal-directed saccadic eye movements needs the previous allocation of endogenous attention at the target location. Here, we investigated the presence and the temporal build-up of this coupling for the initiation of smooth pursuit eye movements (SPEM). Subjects had to report the orientation of a Gabor patch located 7° above or below a horizontally moving SPEM target. Endogenous cues indicated the location of the upcoming discrimination target and preceded the SPEM target onset by 550, 350, 250, 150 or 50 ms (SOA). Unlike in classic saccadic dual-task paradigms, no selection among competing SPEM targets was necessary. Cueing effects were therefore due to signal enhancement rather than to external noise reduction. On the one hand, the discrimination performance was improved with valid cues compared to neutral cues and this improvement was independent of SOA. On the other hand, the latency and gain of SPEM initiation was not perturbed when attention was shifted to a peripheral location. A tradeoff analysis indicated no modulation of cuing effects with SPEM latency. However, the presence of the 550 and 350 ms precues increased SPEM latency relatively to a no-precue condition, even when they had to be ignored. Altogether, the results suggest that although SPEM initiation can be influenced by attention-related factors like alertness or task load, it is not spatially coupled to attention. If there is no uncertainty with respect to the location or identity of the SPEM target (as in our experiment) attention may be shifted to other places without incurring a cost.
The two authors were supported by the Swiss National Foundation 10011-107768/1