Santa Lucia - Neurosciences and Rehabilitation Sapienza University of Rome

Proc Natl Acad Sci U S A. 1999 Nov 23;96(24):14124-9

The neurological basis of conscious color perception in a blind patient

We have studied patient PB, who, after an electric shock that led to vascular insufficiency, became virtually blind, although he retained a capacity to see colors consciously. For our psychophysical studies, we used a simplified version of the Land experiments [Land, E. (1974) Proc. R. Inst. G. B. 47, 23-58] to learn whether color constancy mechanisms are intact in him, which amounts to learning whether he can assign a constant color to a surface in spite of changes in the precise wavelength composition of the light reflected from that surface. We supplemented our psychophysical studies with imaging ones, using functional magnetic resonance, to learn something about the location of areas that are active in his brain when he perceives colors. The psychophysical results suggested that color constancy mechanisms are severely defective in PB and that his color vision is wavelength-based. The imaging results showed that, when he viewed and recognized colors, significant increases in activity were restricted mainly to V1-V2. We conclude that a partly defective color system operating on its own in a severely damaged brain is able to mediate a conscious experience of color in the virtually total absence of other visual abilities.

 Download fulltext

This website uses technical cookies and third party cookies. By closing this banner, scrolling this page or by clicking any of its elements you consent to the use of cookies. If you want to know more or refuse consent to all or some cookies, please see the Cookie Policy. TRADUCI IN ITALIANO