Braille reading is a remarkable example of the human brain adopting compensatory strategies following loss of a vital function, namely visual input to language. We propose using whole-brain functional magnetic resonance imaging (fMRI) in congenitally blind, late-onset blind and sighted subjects to investigate the functional anatomy of the sensory and cognitive processes underlying Braille reading. These studies address an on-going debate about whether the blind show increased capacity for processing non-visual information and whether these changes are examples of the brain's adaptive plasticity. The central issue underlying these experiments is investigating possible changes in somatosensory, visual and language areas of the brain that facilitate fluent Braille reading in the blind. We propose six interlocking experiments that involve, in turn, passive somatosensory, active tactile (haptic) and language tasks. The first two experiments focus on responses to passive, controlled somatosensory stimulation in blind vs. sighted subjects. These studies involve tactile discrimination tasks and a low-level lexical task of identifying raised block capital letters. The middle two experiments study blind subjects actively reading Braille, first with an emphasis on haptic pattern recognition and then higher-level semantics (word meaning). The last two experiments again involve blind and sighted subjects, now performing semantic and phoneme (word sound)tasks in response to heard words. The first and last two experiments examine similarities and differences in the organization of sensory and language systems in blind and sighted subjects performing non-Braille tasks, without visual and motor performance bias. In addition, these experiments will determine whether Braille reading skill reflects functional cortical changes that are general to somatosensory processing or specific to Braille reading and whether blind and sighted subjects use visual cortex for non-visual tasks in a similar manner. The middle two experiments investigate language skills unique to the blind to determine whether theses subjects have fundamentally modified neural systems or instead access the same cognitive systems as sighted subjects by a different sensory route.
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