In the current study, we asked what role presaccadic attention might play in selecting the motion features of saccade targets and if that would influence slow eye movements that are sensitive to motion. The timing of presaccadic enhancement is brief, peaking 50–100 ms before saccades (Deubel, 2008 Li et al., 2016 Ohl et al., 2017 Rolfs & Carrasco, 2012 Rolfs et al., 2011). For example, presaccadic enhancement is unavoidable even when it would be beneficial to deploy attention to other locations in the scene (e.g., by cueing a nontarget location before the saccade Deubel, 2008 Montagnini & Castet, 2007). The enhancement associated with presaccadic attention is involuntary and occurs even when contrary to task demands.
The tuning for stimulus orientation has also been found to sharpen specifically at the saccade target (Ohl, Kuper, & Rolfs, 2017), and there is an enhancement for high spatial frequency features (Li, Barbot, & Carrasco, 2016). The orientation sensitivity and perceived contrast for targets immediately before saccades are increased (Rolfs & Carrasco, 2012). Saccade planning is associated with a perceptual enhancement of the saccade target, called presaccadic attention (Deubel & Schneider, 1996 Kowler, Anderson, Dosher, & Blaser, 1995 Rolfs, Jonikaitis, Deubel, & Cavanagh, 2011 White, Rolfs, & Carrasco, 2013). These results suggest that presaccadic attention selects motion features of targets predictively, presumably to ensure successful immediate tracking of saccade targets in motion. Finally, the PFR magnitude related linearly to the logarithm of stimulus velocity and generally had low gain, similar to involuntary ocular following movements commonly observed after sudden motion onsets. Motion from 50–100 ms prior to the saccade had the strongest influence on PFR, consistent with the time course of perceptual enhancements reported in presaccadic attention. This postsaccadic following response (PFR) increased with spatial uncertainty of the target position and persisted even when we removed the motion stimulus in midflight of the saccade, confirming that it relied on presaccadic information. In this task, saccades were deviated along the direction of target motion, and the eyes exhibited a following response upon saccade landing. Does this presaccadic attention recruit smooth eye movements automatically? To test this, we had human participants perform a saccade to one of four apertures, which were static, but each contained a random dot field with motion tangential to the required saccade.
Saccade planning involves an involuntary enhanced processing of the target, called presaccadic attention. Although prediction is crucial to voluntary pursuit, it is unclear whether it is an obligatory feature of saccade planning. To compensate for delays in processing, saccades to moving targets require predictions: The eyes must intercept the target's future position to then pursue its direction of motion. Saccadic eye movements sample the visual world and ensure high acuity across the visual field.
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