ENSEMBLE MODELS OF THE MOVEMENT AFTEREFFECT AND THE INFLUENCE OF ECCENTRICITY

Moving random-pixel arrays (RPAs) were used to study the movement aftereffect (MAE) for translational texture motion and to quantify the contribution of RPA-sensitive motion sensors to the MAE as a function of eccentricity. Size-scaled patterns were used to make a fair comparison across eccentricities. At the upper end of the velocity range it was found, for all eccentricities, that motion sensors tuned to velocities exceeding about 10-20 deg s-1 do not contribute to the translational MAE, even though they do contribute to motion perception. As a consequence the subpopulation of local motion sensors contributes to the MAE shrinks with eccentricity, because there are fewer low-velocity-tuned and more high-velocity-tuned motion sensors for increasing eccentricity. Thus there is a quantitative, but not a qualititative, difference between the MAEs generated at different eccentricities.