THE SPATIAL GRAIN OF MOTION PERCEPTION IN HUMAN PERIPHERAL-VISION

Motion reversal effects (the apparent reversal of the direction of mot ion of a high frequency sinusoidal grating) have been attributed to al iasing by the cone mosaic [Coletta et al, (1990), Vision Research, 30, 1631-1648] and postreceptoral layers [Anderson & Hess (1990). Vision Research, 30, 1507-1515] in human observers. We present data and a new model which suggest that at least two sampling arrays of different de nsities affect direction discrimination out to 30 degrees eccentricity . The first sampling layer matches anatomical estimates of the cone de nsity. The second sampling layer is too dense to be the parasol cells alone; midget ganglion cells certainly contribute to this task. This i s further evidence that motion perception is not mediated exclusively by the magnocellular stream. Copyright (C) 1996 Elsevier Science Ltd.