Microsaccadic Efficacy and Contribution to Foveal and Peripheral Vision

Abstract

Our eyes move constantly, even when we try to fixate our gaze. Fixational eye movements prevent and restore visual loss during fixation, yet the relative impact of each type of fixational eye movement remains controversial. For over five decades, the debate has focused on microsaccades, the fastest and largest fixational eye movements. Some recent studies have concluded that microsaccades counteract visual fading during fixation. Other studies have disputed this idea, contending that microsaccades play no significant role in vision. The disagreement stems from the lack of methods to determine the precise effects of microsaccades on vision versus those of other eye movements, as well as a lack of evidence that microsaccades are relevant to foveal vision. Here we developed a novel generalized method to determine the precise quantified contribution and efficacy of human microsaccades to restoring visibility compared with other eye movements. Our results indicate that microsaccades are the greatest eye movement contributor to the restoration of both foveal and peripheral vision during fixation. Our method to calculate the efficacy and contribution of microsaccades to perception can determine the strength of connection between any two physiological and/or perceptual events, providing a novel and powerful estimate of causal influence; thus, we anticipate wide-ranging applications in neuroscience and beyond.

Are the visual transients from microsaccades helpful? Measuring the influences of small saccades on contrast sensitivity

“…However, studies on image fading commonly use low-frequency stimuli, and the global reduction in contrast sensitivity measured under prolonged retinal stabilization is more pronounced at low spatial frequencies. It has been recently observed that visibility of a 0.2 cycles/deg is enhanced by saccades larger than 30′, but that smaller saccades only have a very modest effect (McCamy et al, 2012). These previous results are in agreement with the findings of Fig.…”

Suppressive interactions underlying visually evoked fixational saccades

“…A saccade was identified when the eye-movement velocity exceeded this threshold for 7 ms (7 consecutive eye-position samples). We also imposed a minimum intersaccadic interval (defined as the interval between the last sample of one saccade and the first sample of the next saccade) of 10 ms so that potential overshoot corrections were not considered new fixational saccades (McCamy et al, 2012; Møller, Laursen, Tygesen, & Sjølie, 2002). Eye velocity during blink intervals was ignored when calculating the threshold.…”

The unsteady eye: an information-processing stage, not a bug

“…It has long been suggested that microsaccades serve a special role in preventing perceptual fading [8, 33], but this popular hypothesis has remained controversial among researchers [1, 31, 32, 34, 35, 36], and visual impairments similar to those occurring with larger saccades have been observed at the time of microsaccades [37, 38, 39, 40]. Recent studies have shown that when observers are not required to maintain fixation—an unnatural laboratory condition—but are left free to normally move their eyes, microsaccades precisely shift gaze toward nearby interesting locations [41].…”