Motion perception during saccadic eye movements

Abstract

During rapid eye movements, motion of the stationary world is generally not perceived despite displacement of the whole image on the retina. Here we report that during saccades, human observers sensed visual motion of patterns with low spatial frequency. The effect was greatest when the stimulus was spatiotemporally optimal for motion detection by the magnocellular pathway. Adaptation experiments demonstrated dependence of this intrasaccadic motion percept on activation of direction-selective mechanisms. Even two-dimensional complex motion percepts requiring spatial integration of early motion signals were observed during saccades. These results indicate that the magnocellular pathway functions during saccades, and that only spatiotemporal limitations of visual motion perception are important in suppressing awareness of intrasaccadic motion signals.

The old-but-new theories about human voluntary motor control

“…Consistent with their finding, the variable Θr could serve as more direct evidence to show that gaze during saccades is not tied to what is actually falling on the fovea, but instead is tied to the target position, where the fovea will be placed once a saccade is completed. Besides the saccadic suppression mechanism(s) proposed previously 3,4,20,24) , this scheme may account for our inability to see our own eyes in the 'mirror paradigm', since our gaze during saccades is mostly tied to a target falling on the peripheral retina, where spatial resolution decreases rapidly relative to the fovea.…”

“…Since its first documentation in Erdmann and Dodge's report in 1898, this 'mirror paradigm' has been widely cited to illustrate the saccadic suppression phenomenon [17][18][19] . Many researchers support the notion that our inability to see our own eye movements during saccades is of central origin; viz., from factors arising from a CD of the eye movement command, which instructs the visual system to suppress its sensitivity 3,4) ; others suggest that such a central process is unnecessary, and that saccadic suppression can be attributed to peripheral (retinal) processes 20) . Besides such divergent accounts for the same phenomenon, the 'mirror paradigm' poses a practical difficulty from two perspectives: 1. eye displacements which are small relative to the size of the saccades are least likely to be detected by the gazing observer 21) , and 2. even in larger saccades the actual gaze during saccadic periods is not directed to either of the two eyes but to the open space between them, simply suggesting a limitation of space and time available for an intrasaccadic percept of our own eye(s) in motion.…”

Apparent motion during saccadic suppression periods

“…Most previous studies of trans-saccadic displacement or trans-saccadic motion perception have used small stimuli. For instance, Bridgeman et al (1975) studied the displacement of a 13 £ 13° Weld of dots and others have used dot, grating or line stimuli (Campbell and Wurtz 1978;Brooks et al 1980;Burr et al 1982;Ilg and HoVmann 1993;Castet and Masson 2000). In this study, we studied saccadic sensitivity to displacement of a large-Weld display.…”

“…Interestingly, if the retinal image motion normally presented during saccades is compensated for by imposed image motion to retinally stabilize the display, then subjects can see the high frequency stabilized images that would normally be subject to motion blur (Castet and Masson 2000;Garcia-Perez 2001). In fact, saccadic suppression seems to be most pronounced at lower spatial frequencies that would be spared contrast reduction due to motion blur during the saccade (Burr et al 1994;Ross et al 1996).…”

“…Experiments with simulated saccadic image motions displayed during Wxation though have demonstrated that some stimuli are not apparent during saccades that are visible during simulated saccades suggesting active suppression (Diamond et al 2000). Conversely, some stimuli can be seen better during saccades if the eye movement reduces the instantaneous retinal velocity or temporal frequency of the target (Castet and Masson 2000).…”