Abstract
How does the visual system maintain an accurate perception of motion in the world during smooth pursuit eye movements? Previous research suggests there is a recalibration mechanism that shifts the point of subjective stationarity (PSS) to correspond to the predominant background motion experienced during previous eye movement episodes. This recalibration mechanism could act globally and shift estimates across the visual field. We examined this possibility by repeatedly showing the same background motion relative to the pursuit direction in one location (upper or lower visual field, 5 deg eccentricity) and measuring the PSS in the same or opposite visual field. During recalibration trials, observers pursued a dot moving horizontally (7.6 deg/sec) and background motion was shown for 200 ms through a horizontal aperture (30 x 4 deg). On different sessions the background moved at 5 deg/sec either in the direction of pursuit or against it, resulting in retinal velocities of -2.6 and -12.6 deg/sec respectively. On test trials, 30% of the total, we mapped the PSS by varying background velocity and asking whether background motion was perceived leftward or rightward in the world. We found recalibration: a shift in the PSS in the direction of background motion relative to a control in which only test trials were shown. This effect was specific to the location that was stimulated during recalibration trials, therefore ruling out a global recalibration mechanism. Further experiments are underway to determine the spatial tuning of the recalibration, with the aim of comparing to the spatial tuning of the cells in medial superior temporal (MST) cortex that encode motion in the world during pursuit eye movements.
Meeting abstract presented at VSS 2016