[討論] fMRI的內馬爾問題?

[mulkcs (mulkcs)]

Functional Neuroimaging’s Neymar Problem


As a “World Cup tie in post” this one’s a bit late, but here’s a story
that’s been getting a lot of attention: According to scientists, Neymar uses
instinct and not his brain when playing football

Yes, if you believe the headlines, research has shown that legendary
Brazilian forward Neymar da Silva Santos is so good, he can play with his
brain switched off.

What’s the reality? The research in question used fMRI and it was published
in Frontiers in Human Neurosciences: Efficient foot motor control by Neymar’
s brain, by Eiichi Naito and Satoshi Hirose. The free full text is here.

Anyway, the study didn’t quite find Neymar to be some kind of brainless
soccer zombie, but the results were remarkable nonetheless. Naito and Hirose
write:
We scanned Neymar’s brain activity while he rotated his right ankle. We also
scanned three other professional footballers, two top swimmers, and one
amateur footballer, all of whom performed the identical task.
We found activations in the left foot motor cortex regions during the foot
movements in all participants. However, the size and intensity of [foot motor
cortical] activity was smaller in the four professional footballers than in
the three other participants, and Neymar’s activity was smallest of all.
In other words, while performing a football-related motor task (ankle
rotation), the pro footballers showed less neural activity than other
athletes. And Neymar, one of the best players in the world, showed the least
brain activity.

This study was just about one very simple movement – so the headlines
claiming that Neymar uses less brainpower to play football were extrapolating
wildly. There’s more to soccer than twitching your ankle. Nonetheless, the
basic paradox remains – we see less brain activity in people with more
expertise.

This is not a new discovery, but Naito and Hirose provide a great
illustration of the phenomenon, which one might call the Neymar Effect.
For me, the Neymar Effect is a deeply disturbing one, because it seems to
undermine the logic of many fMRI studies. Suppose you scan some patients with
a disorder, and some healthy people, performing some task. You find that on
average the patients show reduced activity in a certain area, compared to the
controls. What does that mean?

The intuitive interpretation is that less activity in a brain region means
less engagement of that brain region’s function. So if the region’s
function is ‘memory’, say, it would be natural to read reduced activity as
less remembering. The results mean that the patients are not remembering as
well as the controls are.

In other words, it is natural (and very common) to start from neural activity
and draw conclusions about psychological processes. A swathe of the fMRI
literature is based on this approach. But the Neymar Problem is that any
given dampening (or excess) of activity could just as easily reflect more
(less) efficient processing, rather than less (more) processing per se. So
the inference from activity to psychology is invalid.

This is a separate issue from the fallacy of reverse inference, which
concerns how we ascribe ‘functions’ to brain regions. The Neymar Effect
means that even if our assumptions about the localization of function are
unerring, we still might go astray when it comes to interpreting quantitative
differences in activity.

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原文:
http://blogs.discovermagazine.com/neuroskeptic/2014/07/31/neymar-zombie-footballer/

論文
http://journal.frontiersin.org/Journal/10.3389/fnhum.2014.00594/full

文章大意是說有科學家找內馬爾來做動右腳踝的fMRI study.
做了七個人，四個是專業足球員，三個是一般人。
四個足球員的左側運動皮質反應比三個一般人來的低，
又以內馬爾的最低。

這和一般fMRI常用的邏輯不同，一般我們會認為活化比較多，
表示運用此資源比較多，表示此功能比較出色。
但這研究和這想法不同。

這篇文章的作者闡述這樣的現象。
但我自己認為有做過fMRI的人都很常碰到一個問題，
行為表現好的，有時候反而是腦區反應比較低的。
這個在解釋上，目前學界是朝向compensate，補償效應來解釋。
因為不專業的人需要活化更多相關腦區來輔助完成這個工作。
這也很合理，畢竟專家或許就表示用更少資源做一樣的事情，也就是更有效率的意思。
但是這在fMRI上，就造成困擾，到底是否反應越高越好呢?
所以我會傾向看fMRI不要只看大腦圖就好，可能要搭配其他資料一起看。



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※ 文章網址: http://www.ptt.cc/bbs/Cognitive/M.1407144738.A.E07.html
推 vsdvd:這個系列其實還有測哈維和伊涅斯塔 XD
→ vsdvd:但是另一個方面來看 足球比賽中還有很多比動腳裸更重要的事
→ vsdvd:自己的 動作 走位 隊友的位置 對手的位置
→ vsdvd:所以花越少資源在單純的身體動作上 在場上越能顧全大局
→ vsdvd:這大概就是球評常說的:踢球要帶上腦袋的意思 XD
→ vsdvd:所以如果是dual task 我想內馬爾在另一個作業上的反應
→ vsdvd:就會比其他人高了 這樣的話就回到了反應越高越好的模式了
→ vsdvd:例如一邊動腳裸 一邊做快速判斷的作業 我猜內馬爾的RT會最快
→ mulkcs:原來還有其他系列....
推 vsdvd:沒錯 像哈維就是空間認識能力好 所以不管資料是長什麼樣子
→ vsdvd:也許重點還是到底要驗證什麼假設和怎麼決定測量哪個部位吧?
推 bisconect:
推 ksm: 有趣