The valleys of the brain

We have been told many times that the wrinkles in our brain corresponds to intelligence and memory power. I even remember an advertisement of a herbal preparation that claimed to increase it to boost memory power! That theory means that a newborn's brain will be as smooth as a boiled egg and that of an old person, like a honey comb! Also whales and elephants have larger and wrinklier brains than us. When was the last time a whale landed on the moon???

To find the origin of brain wrinkles (scientifically: sulci and gyri), a team of Harvard researchers modeled how the brain develops in the embryo using numerical simulations of a growing elastic medium, as well as physical models of the process using “swelling” gels. The outer gray matter consists mostly of neuron bodies, while the white matter underneath consists mostly of axons, which are the extensions of neurons that allow them connect to each other. The researchers placed a layer of gel (for gray matter) on top of a solid hemisphere of gel (for white matter). 

It turns out that the infoldings form due a mechanical instability caused by the expansion of grey matter, while at the same time making it constricted by the white matter. The neuron cell bodies continue to grow but they cannot simply leave the constrains of their own axons. 

Picture the same type of trees growing over a hill. The trees can grow as much as they want, but the topography of the hill will be  preserved. So a valley between the hills will be completely covered by them leaving it looking like a narrow ridge.

Another function of the in-foldings is apparently shock absorption. Imagine the ridges and grooves like that of the pitches of a stretched spring. In a rare event, like a drunken bar fight, a sudden jolt to the skull causes the brain to jerk in the opposite direction and hit the cranial wall. The gyri that first made the collision may move about the space around it, absorb the shock and save other parts of the brain. However this causes a condition known as Concussion which requires medical attention.

So, is there any real function for these infoldings? Nobody knows. Is intelligence related to brain size? Nobody knows. How does the brain work altogether? Nobody knows.

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