02 Nov

Gender on the Neocortex

Mean Bean Counter

The moment a speaker starts “the human brain is the most complex thing in the Universe”, I lose all respect for them.  I am sure they have turned every rock in the Universe and looked underneath before making such a tall claim.  Or, why can’t they perceive that two human brains is more complex than one human brain.  Or, how exactly do they define complexity?  Or brain?

Similarly, when someone says that we use only 10% of the our brain, you can immediately conclude that this person doesn’t understand evolution.  Since we know that human brain is an energy-expensive organ in the body, and that evolution just won’t build such a wasteful organ.

Another brain myth, but less well knows is the number of cells we carry in the brain: 100 billion neurons and 1 trillion glial cells (neurons do the thinking and glial cells do the housekeeping).  But recent studies give us very reliable cell count in the brain.  We know know that we have about 85 billion neurons and 86 billion glial cells.  In all, about 170b in total.  Not the originally claimed 1,100b.

We humans are very proud of our huge cerebral cortex.  We believed that it is brimming with neurons.  Even though our cerebral cortex occupies 80% of the brain, it has only 20% of total neurons!  Interestingly, the cerebellum (‘small brain’ in Latin), a small inconsequential bulb of the brain that hangs behind the big-mean-cerebral cortex, contains 80% of all the neurons; whereas it is only 10% by volume!  By the way, we only have a vague idea of what cerebellum does.  The state of the art in neuroscience is truly embarrassingly primitive.

We love to think that the human brains are somehow different from rest of the primates.  Anatomically speaking, the only difference between us and other primates is the brain size.  Human brain seem to be just a blown up version of monkey brains.

I save the best for the last: In the neocortex (the seat of human uniqueness, including intellect and executive functions), men have 21% more neurons than women (23b/19b) and 33% (65b/49b) more glial cells!  I don’t think anyone knows what to make out of this information because men and women have very similar average IQ.

Of course, I don’t know the significance any of the other information in this post either.  At this point in time, all of them seem to be completely useful pieces of trivia.  But I will end up remembering them anyway.  You, my reader, I am sure you will end up remembering at least the last one for sure!