Three-systems theory of human visual motion perception: review and update

Lu and Sperling [Vision Res. 35, 2697 (1995)] proposed that human visual mo tion perception is served by three separate motion systems: a first-order s ystem that responds to moving luminance patterns, a second-order system tha t responds to moving modulations of feature types-stimuli in which the expe cted luminance is the same everywhere but an area of higher contrast or of flicker moves, and a third-order system that computes the motion of marked locations in a "salience map," that is, a neural representation of visual s pace in which the locations of important visual features ("figure") are mar ked and "ground" is unmarked. Subsequently, there have been some strongly c onfirmatory reports: different gain-control mechanisms for first- and secon d-order motion, selective impairment of first- versus second- and/or third- order motion by different brain injuries, and the classification of new thi rd-order motions, e.g., isoluminant chromatic motion. Various procedures ha ve successfully discriminated between second- and third-order motion (when first-order motion is excluded): dual tasks, second-order reversed phi, mot ion competition, and selective adaptation. Meanwhile, eight, apparent contr adictions to the three-systems theory have been proposed. A review and rean alysis here of the new evidence, pro and con, resolves the challenges and y ields a more clearly defined and significantly strengthened theory. (C) 200 1 Optical Society of America.