台大心理系

Color is one of the fundamental aspects of visual information,but little is known about how color information is coded in human brains. We first addressed to this issue by using a functional brain imaging technique with MRI scanner (fMRI). The histogram of hue selectivity in human visual cortex was measured by using a modified method of phase encoding technique. We found abundant hue selective voxels in various hues. We also confirmed that these hue selectivity in intermediate hues is not weighted sums of outputs from cone-opponent mechanisms, by using a selective adaptation technique in fMRI. On the other hand, people use words when communicate about color in daily life; we do not use chromatic coordinates. We tried to clarify whether the acquisition of color categories, each of which corresponds to a color term, is fully depending on language or not. Cortical responses in infants were recorded by near infrared spectroscopy(NIRS) in occipital area (OC; lowerlevel) and occipito-temporal area (OT:higherlevel), while they were exposed to stimuli that changed colors either between blue and green or between two shades of greens. OT responses showed significant difference between color pairs in both hemispheres, but OC response did not. Similar results were found in adults. These studies tells that color representations are not just red-green/yellow-blue components; there are different types of color representation in human visual cortex. The color categories seem to develop independent of language acquisition, but the way how they are build up from cone responses are still an open question.