Unfortunately this question, at this time in our understanding of neuroscience, is so ill-posed that the only response [1] this neuroscientist-in-training can give (in the 2 minutes I have allotted to the task) is to agree with Joshu [2] and shout, "MU!"

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[1] Well, okay, the only response that I find both cogent and fun to write.

[2] http://peterspearls.com.au/mu.htm