Abstract
Fixational eye movements serve two competing functions: the stabilization of the current gaze position and the generation of retinal image slip to counteract photoreceptors adaptation. In laboratory measurements of eye movement, participants are typically restrained in their head movements, which might bias the functional role of fixational eye movements towards the generation of retinal refresh. Here we compare fixational eye movement statistics measured during upright standing with eye movements recorded with restrained head. Simultaneously with the recordings during standing we collected data from the movement of the center of pressure. Both types of movements are governed by temporal scaling properties with persistent behavior on the short time scale and antipersistent behavior on the long time scale. However, the transition points between scales are observed at different ranges. We show that changing the posture strongly modulates the scaling properties of fixational eye movements. Finally, we discuss possible models of the control of fixational eye movements.