Blind people have some advantages over sighted people, perhaps because the blind have so much experience in substituting other abilities for vision. For instance, their sense of touch is more sensitive, and they are superior at verbal memory. Zohary and colleagues suggest an anatomical basis for the latter ability in the July issue of Nature Neuroscience, by finding brain activity in the primary visual cortex of blind people performing a verbal memory task without any sensory input.
The finding is surprising because primary visual cortex is normally thought to be involved in a very early stage of sensory processing. Although previous work has shown that primary visual cortex receives input from other senses - touch and hearing - in blind people, it had not been shown to participate in non-sensory processing. The authors found that memory-related activation was stronger in the left hemisphere, in agreement with the left lateralization of language functions in other brain areas. The activation (measured by functional magnetic resonance imaging) correlated with individual verbal memory performance: the higher the visual cortex activation, the better the subject’s verbal memory, both on the tests done in the scanner and in a test of overall memory abilities. That correlation suggests that the activity seen in primary visual cortex may be important for verbal memory in the blind.
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