|MadSci Network: Neuroscience|
In many small animals such as frogs, birds, and rats, the cortex of the brain is perfectly smooth. In larger animals like humans, there is a need for as much cortex as possible, so the cortex becomes folded into gyri and sulci to provide as much surface area as possible for it. There is a brain disorder, lissencephaly, in which the cortex is smooth and there is impaired brain function. This is due to an abnormal protein, Lis1, that regulates the function of cilia. Apparently, an impaired function of cilia in the embryonic brain results in an impaired migration of neurons and a smooth cortex (see Pedersen LB, Rompolas P, Christensen ST, Rosenbaum JL, King SM "The lissencephaly protein Lis1 is present in motile mammalian cilia and requires outer arm dynein for targeting to flagella" Journal of Cell Science, vol. 120, p. 858, 2007). You can access this article by going to the website www.pubmed.gov.
Why people prefer smooth surfaces is a good question. Rough surfaces, of course, can have dangerous splinters and may feel unpleasant. The roughness of a surface is assessed via special receptors in the fingers called Pacinian corpuscles.
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