No abstract

Contrary to common wisdom, fixations are a dynamically rich behavior, composed of continual, miniature eye movements, of which microsaccades are the most salient component. Over the last few years, interest in these small movements has risen dramatically, driven by both neurophysiological and psychophysical results and by advances in techniques, analysis, and modeling of eye movements. The field has a long history but a significant portion of the earlier work has gone missing in the current literature, in part, as a result of the collapse of the field in the 1980s that followed a series of discouraging results. The present review compiles 60 years of work demonstrating the unique contribution of microsaccades to visual and oculomotor function. Specifically, the review covers the contribution of microsaccades to (1) the control of fixation position, (2) the reduction of perceptual fading and the continuity of perception, (3) the generation of synchronized visual transients, (4) visual acuity, (5) scanning of small spatial regions, (6) shifts of spatial attention, (7) resolving perceptual ambiguities in the face of multistable perception, as well as several other functions. The accumulated evidence demonstrates that microsaccades serve both perceptual and oculomotor goals and although in some cases their contribution is neither necessary nor unique, microsaccades are a malleable tool conveniently employed by the visual system.

Many cells in retinotopic brain areas increase their activity when saccades (rapid eye movements) are about to bring stimuli into their receptive fields. Although previous work has attempted to look at the functional correlates of such predictive remapping, no study has explicitly tested for better attentional performance at the future retinal locations of attended targets. We found that, briefly before the eyes start moving, attention drawn to the targets of upcoming saccades also shifted to those retinal locations that the targets would cover once the eyes had moved, facilitating future movements. This suggests that presaccadic visual attention shifts serve to both improve presaccadic perceptual processing at the target locations and speed subsequent eye movements to their new postsaccadic locations. Predictive remapping of attention provides a sparse, efficient mechanism for keeping track of relevant parts of the scene when frequent rapid eye movements provoke retinal smear and temporal masking.