Research Abstract:
Blind people who read Braille illustrate compensatory strategies to maintain literacy. We have used functional MR imaging (fMRI) to investigate these special adaptations. Our studies have found that adaptive changes involve cross-modal activation of visual cortex and altered response dynamics in several non-visual cortical areas. We have examined whether cross-modal cortical changes in blind people are general to processing tactile information or specific to Braille reading, and whether blind and sighted subjects use visual cortex comparably for non-visual tasks. We found responses in visual cortex when blind people read nouns through Braille for a verb generation task. Similar activation of visual cortex was found when blind, but not sighted people, generated verbs to heard nouns. Semantic language tasks, like verb generation, engaged visual cortex more extensively than simpler phonological, rhyming tasks. These findings suggest that language information obtained through touch or sound engages visual cortex in blind people. Recent studies, however, showed visual cortex activation during tactile stimulation tasks alone. The pattern of activation differed topographically, which possibly indicated that separate domains in reorganized visual cortex support different cognitive and perceptual processes. New fMRI studies probe potential visual cortex domain specialization in blind people that support semantic vs. sublexical language processes and memory processes for tactile stimuli or words. One issue considered in upcoming studies is whether learning words through Braille or listening leads to differences in retention and distinctive cortical activation patterns.
Selected Publications:
Burton H, Sinclair, RJ, Wingert JR, Dierker d Multiple parietal operculum subdivisions in humans: tactile activation maps. Somatosens Mot Res 2008 25: 149-162.
Burton H, Sinclair, RJ, McLaren, DG Cortical network for vibrotactile attention: A fMRI study. Hum Brain Mapp 2007 29: 207-221.
Burton H and McLaren DG. Visual cortex activation in late-onset, Braille naive blind individuals: An fMRI study during semantic and phonological tasks with heard words. Neurosci Letts 2006 392: 38-42.
Burton H, McLaren DG and Sinclair RJ. Reading embossed capital letters: a fMRI study in blind and sighted individuals. Hum Brain Mapp 2006 27: 325-339.
Burton H, Sinclair RJ, McLaren DG. Cortical activity to vibrotactile stimulation: A fMRI study in blind and sighted individuals. Hum Brain Mapp 2004 23: 210-228.
Last Updated: 08/11/2009 |