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zoom RSS 人にもコウモリのような音波探知能力がある

<<   作成日時 : 2011/06/02 23:43   >>

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 「コウモリのように見る」ことができる人が使う脳部位がカナダの研究者により同定されたという。目が不自由な人の中には、クリック音を立てて反響音を聞くことでecholocation反響定位ができるようになった人がいる。視野に関連した脳部位が反響音を聞くときに活性化されることが示されたという。
 コウモリやイルカがこうした方法で世界を「見る」ことができることが知られている。
 音波探知ができる2人の患者(13ヶ月で失明した43歳、14歳で失明した27歳)を検査したところ、fMRIで後頭葉鳥距野(calcarine cortex)が活性化されるのがわかった。2人とも非常に似た方法で音波探知をしていた。
 視覚障害者の訓練の手助けになるかもしれない。

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26 May 2011 Last updated at 08:09 GMT
Human brain's 'bat sight' found
http://www.bbc.co.uk/news/health-13539921

画像The part of the brain used by people who can "see like a bat" has been identified by researchers in Canada.

Some blind people have learned to echolocate by making clicking noises and listening to the returning echoes.

A study of two such people, published in PLoS ONE, showed a part of the brain usually associated with sight was activated when listening to echoes.

Action for Blind People said further research could improve the way the technique is taught.

Bats and dolphins bounce sound waves off their surroundings and by listening to the echoes can "see" the world around them.

Some blind humans have also trained themselves to do this, allowing them to explore cities, cycle and play sports.
Brain scan

Researchers looked at two patients who use echolocation every day. EB, aged 43, was blinded at age 13 months. LB, 27, had been blind since age 14.

They were recorded echolocating, while microphones were attached to their ears.

The recordings were then played while their brain activity was being recorded in an fMRI machine.

Increased activity in the calcarine cortex was discovered.

Dr Lore Thaler, from University of Western Ontario, said: "This suggests that visual brain areas play an important role for echolocation in blind people."

The study looked at only two people so cannot say for certain what happens in the brains of all people who learn the technique, but the study concludes: "EB and LB use echolocation in a way that seems uncannily similar to vision."

Susie Roberts, rehabilitation officer at Action for Blind People, said: "This research into brain activity and echolocation is very interesting and improves our understanding of how some visually impaired people may be processing information to help them navigate safely.

"Further investigation may help to improve the way the technique is taught to people in the future, potentially improving their mobility and independence."

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Neural Correlates of Natural Human Echolocation in Early and Late Blind Echolocation Experts
Lore Thaler1, Stephen R. Arnott2, Melvyn A. Goodale1*

PLoS ONE 6(5): e20162. doi:10.1371/journal.pone.0020162

1 Department of Psychology, University of Western Ontario, London, Ontario, Canada, 2 Rotman Research Institute, Baycrest, Toronto, Ontario, Canada
Abstract Top
Background

A small number of blind people are adept at echolocating silent objects simply by producing mouth clicks and listening to the returning echoes. Yet the neural architecture underlying this type of aid-free human echolocation has not been investigated. To tackle this question, we recruited echolocation experts, one early- and one late-blind, and measured functional brain activity in each of them while they listened to their own echolocation sounds.
Results

When we compared brain activity for sounds that contained both clicks and the returning echoes with brain activity for control sounds that did not contain the echoes, but were otherwise acoustically matched, we found activity in calcarine cortex in both individuals. Importantly, for the same comparison, we did not observe a difference in activity in auditory cortex. In the early-blind, but not the late-blind participant, we also found that the calcarine activity was greater for echoes reflected from surfaces located in contralateral space. Finally, in both individuals, we found activation in middle temporal and nearby cortical regions when they listened to echoes reflected from moving targets.
Conclusions

These findings suggest that processing of click-echoes recruits brain regions typically devoted to vision rather than audition in both early and late blind echolocation experts.


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