Blindness and brain plasticity: contribution of mental imagery? An fMRI study

The purpose of this study was to study brain plasticity in the visual cortex, in six subjects totally blind from birth. The protocol we used was the same as that employed in a prior study on blindfolded sighted subjects (Brain Res., 924 (2002) 176). The production of mental images from animal names versus passive listening to abstract words, involved, in the early blind subjects as well as in the blindfolded sighted subjects of our control group, the superior occipital, inferior and superior parietal areas, premotor area, visual association. Activation foci in the somatosensory areas in the left hemisphere, as well as in the temporal and fusiform gyri were only visible in the blind subjects. The experiment, which was repeated after a short period of rest, demonstrated, this time again, predominant involvement of the dorsal pathway and activation of the primary visual area (in a region of interest). With respect to the ongoing debate on brain reorganization, our study shows that the primary visual area is activated in early blind subjects, and that activation persists in a mental imagery task involving no sensory input other than verbal instructions.