The eyes are continuously fluctuating even during fixation. The fluctuations are called miniature eye movements and consist of microsaccades, drifts, and tremors. It has been revealed that these miniature eye movements aid our vision. Although the functional roles of the miniature eye movements have gradually been uncovered, their generation mechanism remains a mystery. Here, we focus on the microsaccade, and review the related neuronal circuit, and generation mechanisms from the viewpoint of neurophysiology and computational neuroscience.
The vestibule-ocular reflex (VOR) is a fast reflex with machine-like features that stabilizes vision during head movement. The fact that even a reflex as simple and fundamental as the VOR involves a neural delay may imply that we are at least a step behind the reality. However, the VOR is equipped with mechanisms that anticipate the visual consequence of the reflex action to produce appropriate responses in various contexts. That is, the brain maintains a predictive state even at the reflex level. This perspective may lead to further understanding of brain functions.