Does cortical motion adaptation exhibit functional properties analogous tolight adaptation in the retina?

Purpose: The retina codes variations in luminance by adapting to and hence discounting,the mean luminance. During adaptation to a moving pattern, perc eived speed decreases. Thus we know that the adapted visual system does not simply code the absolute speed of a stimulus,We hypothesize that adaptatio n to a moving stimulus serves to optimize coding of changes in speed at the expense of maintaining an accurate representation of absolute speed. in th is case we would expect discrimination of speeds around the adapted level t o be preserved or enhanced by motion adaptation. Methods and results: After adaptation to motion in the same direction as a subsequent test stimulus, seven of eight subjects showed a reduction of per ceived speed in the adapted region and seven showed enhanced discrimination . Conclusions: We conclude that motion adaptation preserves or enhances diffe rential speed sensitivity at the expense of an accurate representation of a bsolute speed in a manner analogous to retinal light adaptation.