Pro- and Antisaccades: Dissociating Stimulus and Response Influences the Online Control of Saccade Trajectories

ABSTRACT

The authors examined whether the diminished online control of antisaccades is related to a trade-off between movement planning and control or the remapping of target properties to a mirror-symmetrical location (i.e., vector inversion). Pro- and antisaccades were examined in a standard no-delay schedule wherein target onset served as the movement imperative and a delay cuing schedule wherein responses were initiated 2,000 ms following target onset. Importantly, the delay cuing schedule was employed to equate pro- and antisaccade reaction times. Online control was evaluated by indexing the strength of trajectory amendments at normalized increments of movement time. Antisaccades exhibited fewer online corrections than prosaccades, and this result was consistent across cuing schedules. Thus, the diminished online control of antisaccades cannot be tied to a trade-off between movement planning and control. Rather, the authors propose that the intentional nature of dissociating stimulus and response (i.e., vector inversion) engenders a slow mode of cognitive control that is not optimized for fast oculomotor corrections.

Keywords:

• antisaccade
• feedback
• online control
• prosaccade
• vision

ACKNOWLEDGMENTS

This research was supported by the Natural Sciences and Engineering Research Council of Canada and a Major Academic Development Fund Award from the University of Western Ontario.

Notes

1. Previous work has documented symmetrical online control for saccade trajectories to targets in left and right space (Heath et al., 2010; see also West et al., 2009). As such, saccade direction (leftward vs. rightward) was not included in our ANOVA model.

2. In Unsworth et al. (2011), participants identified a target stimuli (i.e., the letters B, P, and R) by pressing a specific response key with their hand (i.e., the keys 1, 2, and 3). Following 3,500 trials, response times for anti responses were equivalent to pro responses. However, Unsworth et al. did not measure eye movements; rather, the authors argued that their stimulus set and use of a manual button press task provides a corollary measure of saccade latencies. Moreover, Unsworth et al. required a semantically based response (i.e., press key 1 in response to the appearance of a B).

3. A directionally correct antisaccade entails a response mirror symmetrical to a cued target stimulus. In contrast, a directionally incorrect antisaccade entails a response directed to the veridical location of the cued target stimulus. Importantly, the presetting of the oculomotor system forwarded by Ford et al. (2005) is specific to the former response.