A psychophysical dissection of the brain sites involved in color-generating comparisons

We have used simple psychophysical methods to determine the sites of color- generating mechanisms in the brain. In our first experiment, subjects viewe d an abstract multicolored "Mondrian" display through one eye and an isolat ed patch from the display through the other. With normal binocular/monocula r viewing, the patch has a different color when viewed on its own (void mod e) or as part of the Mondrian display (natural mode) [Land, E. H. (1974) Pr oc. R, Inst. G. B. 49, 23-58]. When the two stimuli were viewed dichoptical ly, with the patch occupying the position that it would occupy in the Mondr ian complex under normal viewing, the patch always appeared in its void col or. In a second experiment, when subjects viewed multicolored displays thro ugh a different narrowband filter placed over each eye, the information fro m the two eyes was combined to result in new colors, which were not seen th rough either of the two eyes alone. Taken together, these results dissect c olor-generating mechanisms into two stages, located at different sites of t he brain: The first occurs before the appearance of binocular neurons in th e cortex and compares wavelength information across space, whereas the seco nd occurs after the convergence of the input from the two eyes and syntheti cally combines the results of the first.