Outflow and inflow in movement duplication

Following prolonged exposure to two vertical grating patterns differing in spatial frequency—one pattern illuminated in green light alternated with the other pattern illuminated in red light—human observers will sometimes report seeing desaturated complementary colors when presented with a neutrally illuminated test field consisting of adjacent halves of the two adapting gratings. The number of such color reports increases as the difference between the spatial frequencies of the adapting gratings increases. This frequency-specific chromatic aftereffect is similar to that obtained with orientation-specific color adaptation and may be mediated by neural “channels,” sensitive to both color and frequency input, which are similar to units known to exist in the visual systems of lower organisms.