先天性視覚障碍者における脳の可塑性

 「Neuron」に掲載された論文によると、先天性視覚障碍者後頭葉視覚野を触覚や聴覚能力を高めるために用いているとのことである。

WEDNESDAY, Oct. 6 (HealthDay News) -- Blind people use the visual part of their brain to heighten their senses of touch and hearing, new research has found.


In the study, published in the Oct. 6 issue of the journal Neuron, researchers used functional MRI to observe brain activity in 12 people who were blind from birth and 12 sighted people as they performed a set of tasks involving hearing and feeling.


"We found that the visual cortex in the blind was much more strongly activated than it was in the sighted, where visual cortex was mostly deactivated by sound and touch," lead investigator Josef P. Rauschecker, a professor in the department of physiology and biophysics at Georgetown University Medical Center, said in a Georgetown news release.


"Futhermore, there was a direct correlation between brain activity and performance in the blind. The more accurate blind people were in solving the spatial tasks, the stronger the spatial module in the visual cortex was activated," Rauschecker added.


He said the findings show that "the visual cortex in the blind takes on these functions and processes sound and tactile information, which it doesn't do in the sighted. The neural cells and fibers are still there and still functioning, processing spatial attributes of stimuli, driven not by sight but by hearing and touch. This plasticity offers a huge resource for the blind."


This helps explain why blind people have such advanced senses of touch and hearing, which far exceed the abilities of sighted people, Rauschecker said.

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 論文の抄録は、Preserved functional specialization for spatial processing in the middle occipital gyrus of the early blind. - PubMed - NCBIにある。


 本研究は、本来視覚関連機能を担う後頭葉視覚野が、触覚や聴覚など別の感覚の連合野として用いられていることを示している。論文そのものを読んでいないので詳細はわからないが、運動学習を通じて近接する体性感覚野や聴覚野が拡大したのではないかと推測する。脳科学の進歩により、脳の可塑性に関する興味深い知見が次々と明らかになってきている。
 Stevie Wonder辻井伸行など視覚障碍をもった音楽家に対して、今回のようなfMRIを用いた研究を行った場合、より顕著な結果が出る可能性がある。今回の研究の発展に期待する。