In contrast to PET and fMRI studies, color-selective responses from
the ventro-occipital area have rarely been reported in MEG studies. We
tried to minimize the stimulation to all areas in the visual system except
the color-processing ones by using a color space based on psychophysical
and physiological knowledge in order to maximize the signal-to-noise ratio
for MEG responses from the ventro-occipital area. MEG obtained from long
intermittent reversals (2.0–3.5 s) of isoluminant chromatic gratings
showed two major peaks at the latencies of approximately 100 and 150 ms.
The estimated location of the equivalent-current dipole for response at
100-ms latency was in the calcarine sulcus and that of the dipole for the
response at 150 ms was in the collateral sulcus in the ventro-occipital
area. The response around 150 ms was uniquely observed in MEG elicited by
chromatic reversals. The average of lags between MEG responses from the
calcarine sulcus and ventro-occipital area was 43 ms, which suggests
sequential processing of color information across the visual cortices.