p315fig08.35 The output signals from the directional grouping network obey the ART Matching Rule.  They thereby select consistent motion directional signals while suppressing inconsistent ones, and do not distort that the spared cells code.  The aperture problem is hereby solved by the same mechanism that dynamically stabilizes the learning of directional grouping cells.<BR>||  How to select correct direction and preserve speed estimates?  Prediction: Feedback from MSTv to MT- obeys ART Matching Rule; Top-down, modulatory on-center, off-surround network (Grossberg 1976, 1980; Carpenter, Grossberg 1987, 1991); Explains how directional grouping network can stably develop and how top-down directional attention can work. (Cavanough 1992; Goner etal 1986; Sekuer, Ball 1977; Stelmach etal 1994). Directional grouping network (MSTv) <-> Directional long-range filter (MT). Modulatory on-center selects chosen direction and preserves speed.  Off-surround inhibits incompatible directions.