Microsaccades keep the eyes' balance during fixation.
During fixation of a stationary target, small involuntary eye movements exhibit an erratic trajectory-a random walk. Two types of these fixational eye movements are drift and microsaccades (small-amplitude saccades). We investigated fixational eye movements and binocular coordination using a statistical analysis that had previously been applied to human posture control. This random-walk analysis uncovered two different time scales in fixational eye movements and identified specific functions for microsaccades. On a short time scale, microsaccades enhanced perception by increasing fixation errors. On a long time scale, microsaccades reduced fixation errors and binocular disparity (relative to pure drift movements). Thus, our findings clarify the role of oculomotor processes during fixation.
Engbert
Ralf
R
Department of Psychology, University of Potsdam, PO Box 601553, 14415 Potsdam, Germany. engbert@rz.uni-potsdam.de
Kliegl
Reinhold
R
D005403:Fixation, Ocular; D006801:Humans; D008954:Models, Biological; D012438:Saccades / Q000502:physiology*; D015348:Vision, Binocular / Q000502:physiology