Rozana Ovsepian¹ (), David Souto, Alexander C. Schütz; ¹University of Marburg

Smooth pursuit eye movements decouple motion on the retina and motion in the environment. To recover motion in external coordinates, the retinal motion may be compensated by the predicted sensory consequences of pursuit. Previous research showed that the size of the pursuit-related reafference signal is continuously updated, based on an interaction between the motor command of the pursuit, and the retinal motion during the eye movement (Haarmeier et al., 2001). Here, we tested if this recalibration is specific to the speed of pursuit or if it generalizes to other speeds. First, we asked subjects to execute horizontal smooth pursuit at a velocity of 8.5°/s. In the middle of the target trajectory, a background pattern moving at 5°/s in a horizontal direction was presented for 200ms. In these exposure trials, the background was moving either in the same direction (Reafference High) or opposite to the direction of the eye movement (Reafference Low). These exposure trials were interleaved with test trials, in which subjects were asked to report the perceived direction of the background motion, the velocity of which was varied with an adaptive staircase procedure to estimate the point of subjective stationarity (PSS). Replicating previous results, the PSS was clearly shifted in the direction of the background speed observed in the exposure trials. Secondly, we investigated how the exposure to background motion during pursuit affected the perceived motion when different pursuit speeds (5.5°/s, 11.5°/s) were used for test and exposure trials (8.5°/s). We found that the recalibration of the reafference signal transferred robustly to lower and higher pursuit speeds and was not restricted to the exposure speed. We propose that the recalibration of the reafference signal might be based on a gain-control mechanism that allows to generalize recalibration to different pursuit speeds.

Acknowledgements: This work was supported by the “The Adaptive Mind,” funded by the Excellence Program of the Hessian Ministry of Higher Education, Science, Research and Art.