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When we assume that peripheral touch receptor densities are equal in tall and short people, then tall people should have more touch receptors than short people, given the larger amount of skin surface in the former. Hence my question:

Do taller people have larger somatosensory cortices than short people? And analogues to that, what about larger motor cortices in tall people? If tall people need larger somatosensory and motor areas, could this imply that they have less space devoted to other functions, like functions devoted to the prefrontal cortex?

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Do you mean mass-corrected size or absolute size? If the latter, then I would say probably due to the laws of scaling. – kmm Jan 23 '12 at 3:18
    
Absolute size. Mass-corrected size would be interesting too though – InquilineKea Jan 23 '12 at 23:11
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If you are interested in the anatomical differences between small and large people, then I'd think you want mass corrected. My brain is larger than my 2-year-old nephew in absolute size, but his is probably larger than mine in relative size. – kmm Jan 24 '12 at 0:09

I would say no.

Your question somehow implies that somatosensory cortex is equally distributed among the different sensory areas of the body, whereas in the reality this is the known "cortical homunculus" concept of how this distribution looks:

cortical homunculus

If you look at this representation you'll see that chest and legs take only about one third to one fourth of the cortex, thus the changes between short and tall people don't seem to have noticeable contribution to the overall cortex size.

If we just walk away from cortex size and discuss the amount of nerve cells in these areas I would say that these numbers should correlate with the number of peripherial receptor cells that provide input for them, and since there is no known changes in receptor density among different body sizes, even the amount of nerve cells seems to be more or less same.

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If there is no change in receptor density, but an increase in body surface area (from being bigger and all) then wouldn't one expect an increase in the number of nerve cells? Basically, I don't understand your last sentence. – Artem Kaznatcheev Jun 17 '12 at 1:33
    
I agree with @ArtemKaznatcheev - The core of the question is whether the density of peripheral mechanoreceptors is identical across people of different posture. If yes, a large person (in length, or otherwise) would have more skin receptors and hence a larger afferent input to the cortex, and hence a larger cortical surface needed, as evident in the homunculus. – Christiaan Jan 25 at 9:43

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