LS: Speaking of Science Columnn November 03, 2008
Thoughts on thinking: What is the brain for?
Humans use the brain for many fascinating activities: solving algebraic problems, writing symphonies, making legal judgments, reading, designing buildings and writing poetry.
Yet these activities are accomplished in a very small portion of the brain. The human brain weighs about three pounds and is a little larger than two clenched fists side by side.
However, only a very small portion of that mass operates under conscious control.
Only the outermost covering, called the cerebrum, is used in doing conscious, voluntary and sometimes creative tasks. The cerebrum is only about as thick as six playing cards stacked together and is, in fact, made up of six layers of cells. These cells are so small, however, that there are around 20 billion cells in these six layers.
One might wonder why it is necessary to have so many cells live in this world. Amoebas seem to get around with a single cell. But there are several big differences between a human and an amoeba.
The first is that we are, well, big! What happens on the right side of an amoeba, whichever side, is not so far from the other side.
But circumstances at the feet of a human may be far different from the circumstances at the head, several feet away.
For example, bare feet on asphalt have a significantly different experience than the head under a straw hat. This information must be communicated to all parts of the body so appropriate adjustments can be made in behavior.
Likewise, moving a larger mass around requires more communication abilities than moving a very small single cell. This is one of the simple reasons for more cells: more and better communication.
Another difference between amoeba and humans is that they are aquatic.
We require water, of course, but we do not live in water; we live on land, in the air, a far less viscous medium than water. But this means that things happen faster on land than in the water and our response time must be a magnitude faster than any amoeba.
As humans we have learned “speed kills.” Response time must be much faster than an amoeba because a fall has far more serious consequences: further distances and greater velocities.
Oh yes, and then there are those pesky appendages.
We have five you know. Two arms, two legs, and a head perched up on top of a stick. In fact, in this respect, we look a little like a starfish I suppose. But running multiple appendages, and keeping the correct foot down before picking the other one up, requires a good deal of internal communication, and more cells.
In fact, the cerebrum with its 20 billion cells is actually only a small fraction of the total number of cells in the nervous system.
Estimates are that the entire brain has about 100 billion cells (and that estimate usually doesn’t include the peripheral neurons).
The great majority of these cells operate below the conscious level, taking care of the internal monitoring and communication needed to monitor a rapidly changing environment, moving appendages and coordinating changes of position in a large structure.
So it appears that much of the brain is actually for sensing the environment and making appropriate automatic and conscious responses.
So maybe the brain isn’t for all that high-powered chess, mathematics, language and music after all.
Maybe the brain is just about getting to the grocery store and back.
Or, maybe these simple abilities to move about, sense changes in a fast-changing world and do complicated tasks has something to do with the unique creative intelligence found in humans.
Maybe our ability to do what we usually think of as thinking is actually dependent on our abilities to do a whole of bunch tasks that we usually don’t think of as thinking at all.
Gary McCallister is a professor of biology at Mesa State College with research interests in infectious diseases and also the biology of the mind.