A COMPUTATIONAL MODEL OF SELECTIVE DEFICITS IN FIRST-ORDER AND 2ND-ORDER MOTION PROCESSING

Recent neurological studies of selective impairments in first and seco nd-order motion processing are of considerable relevance in elucidatin g the mechanisms of motion perception in normal human observers. We ex amine the stimuli which have been used to assess first and second-orde r motion processing capabilities in clinical subjects, and discuss the nature of the computations necessary to extract their motion. We find that a simple computational model of first and second-order motion pr ocessing is able to account for the data. The model consists of a firs t-order channel computing motion at coarse and fine scales, and a coar se scale second-order channel. The second-order channel is sensitive t o motion information defined by variations in luminance, contrast, spa tial frequency and flicker. When elements of the model are disabled, i ts performance on either first or second-order motion can be selective ly impaired in line with the neurological data. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.