From Medical Xpress:
Hue selectivity results: (left) example hue selective voxels, indicated by most selective color in each voxel. (right) Average histogram of hue selective voxels in primary visual cortex (V1: one of the four areas measured in this study) as polar histogram in relative population (%). Four dotted lines indicate unique hues (pure red, blue, green and yellow). Credit: Research Institute of Electrical Communication, Tohoku University
Researchers from Tohoku University’s Research Institute of Electrical Communication and RIKEN BSI have found the presence of neurons in the human brain which can each selectively respond to an intermediate color; not just neurons of red, green, yellow and blue.
It was previously believed that the human visual system encoded color information through combinations of four opponent colors – red/green, yellow/blue – and dark/light components. In this format, orange can be represented as the combination of red and yellow, and purple as a combination of blue and red.
However, recent electrophysiological studies in primates have revealed the presence of neurons in the visual cortex, each of which are selective to intermediate color.
Studies using human participants – through psychophysical and brain-activity-imaging techniques – have also shown indirect evidence of the presence of those neurons, although no direct recording of hue-selective response has yet been made, and the variability and population of neurons selective to intermediate colors have not been reported explicitly in humans.
The research group succeeded in recording neuronal responses selective to intermediate hues in human brains by using a functional MRI technique.