We have previously reported that there are neurons in macaque V1 whose responses correlated with the luminance or the brightness of the surface stimulus covering the entire receptive field (SFN Abstract 1998, 254.15). In order to understand the temporal dynamics of such responses, we compared the response profiles (the way in which surface luminance affects the response) between the early period of the response (120-220 ms from stimulus onset) and the later period (later than 320 ms). We recorded the responses of V1 neurons to various luminances of the surface stimuli while monkeys performed a fixation task. About half of the 120 neurons examined exhibited changes of the response profile across different periods. In about 60% of these neurons, the response profile in the early period had V-shape, that is, the response was dependent on the absolute value of the luminance contrast between the stimulus and the background, whereas that in the later period exhibited monotonic change (increase or decrease) depen...