Intrasaccadic perception triggers pupillary constriction.

Sebastiaan Mathôt,Jean-Baptiste Melmi,Eric Castet

doi:10.7717/peerj.1150

Abstract

It is commonly believed that vision is impaired during saccadic eye movements. However, here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye’s pupil. Participants viewed sinusoid gratings that changed polarity 150 times per second (every 6.67 ms). At this rate of flicker, the gratings were perceived as homogeneous surfaces while participants fixated. However, the flickering gratings contained ambiguous motion: rightward and leftward motion for vertical gratings; upward and downward motion for horizontal gratings. When participants made a saccade perpendicular to the gratings’ orientation (e.g., a leftward saccade for a vertical grating), the eye’s peak velocity matched the gratings’ motion. As a result, the retinal image was approximately stable for a brief moment during the saccade, and this gave rise to an intrasaccadic percept: A normally invisible stimulus became visible when eye velocity was maximal. Our results confirm and extend previous studies by demonstrating intrasaccadic perception using a reflexive measure (pupillometry) that does not rely on subjective report. Our results further show that intrasaccadic perception affects all stages of visual processing, from the pupillary response to visual awareness.

Highlights

It is commonly believed that vision is impaired during saccadic eye movements
Intrasaccadic perception induced pupillary constriction The main result is shown in Fig. 4A, in which pupil size is plotted over time as a function of condition (Intrasaccadic Percept vs No Percept)
We report that intrasaccadic perception triggers a constriction of the eye’s pupil

Summary

Introduction

It is commonly believed that vision is impaired during saccadic eye movements. here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye’s pupil. The spatial frequencies of the gratings were set for each participant and saccade direction separately, based on the peak saccade velocities estimated during the first part of the experiment. In this condition, participants should briefly perceive a static grating during the saccade, as described above (Fig. 3B).

Results

Conclusion