Monday, August 18, 2003 Little Known Facts
My friend Haym Hirsh passed along the following. I tried it, and found that this happens to me (though I realize that it might not be universal). I do not vouch for the neurological explanation (the "same side of our brain" theory), only for the phenomenon:
Proof that the same side of our brain cannot do 2 different things at once...
While sitting at your desk make clockwise circles with your right foot.
While doing this, draw the number "6" in the air with your right hand.
Your foot will change direction.UPDATE: Reader Benjamin Philip, a graduate student in the Brown University Department of Neuroscience writes,
I have an explanation for the hand/foot rotating phenomenon you posted about this morning. . . .
As you seem to have guessed, the side of the brain has nothing to do with it. Rather, the issue is in the spinal cord. There are a few major descending control tracts (I believe the one in question is the lateral corticospinal tract), and "central pattern generators" are a major feature of how they work. The rotating motion involved in tracing a circle probably comes from one of those pattern generator circuits -- but the key fact is that there would a single such circuit
for the tract on each side of the spinal cord, apparently upstream of both arm and leg. The "rotation generator" circuit in the right lateral corticospinal tract can only be doing one thing at a time -- clockwise or counterclockwise. Since most movement patterns are centrally (usually spinal cord) generated, distinctions between arm and leg can be meaningless.
So, rather than "the same side of our brain cannot do two different things at once", the explanation is that "the same side of the spinal cord cannot do the same thing in two opposite directions at once." Volokh Conspiracy -- posted by Chuck at Monday, August 18, 2003 | E-mail | Permalink | Main |
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