Abstract

Observers adapted to 1-cycle/deg sinusoidal luminance defined (yellow/black) gratings tilted 15°CW from the vertical that alternated with 1-cycle/deg color-defined (red/green) gratings tilted 15°CCW from vertical. Subsequently viewed vertical luminance test gratings appeared tilted up to 3°CCW, while chromatic test gratings appeared tilted up to 3° in the opposite direction, demonstrating independent tilt aftereffects for color and luminance. A tilt aftereffect induced by a chromatic stimulus¹ may be mediated by luminance artifacts. However, in our opposing aftereffects procedure,² any aftereffect resulting from residual luminance differences in the chromatic stimuli will be overwhelmed by the adaptation in the opposite direction produced by the luminance stimulus itself—ensuring that the aftereffect seen on the color test is truly mediated by chromatic mechanisms. The induction of simple aftereffects (with luminance gratings or color gratings) transfers to color and luminance tests showing, as well, some overlap in luminance and color processing of orientation. These data, therefore, demonstrate that at least some color selective units in the cortex must also be selective for orientation.

© 1987 Optical Society of America