Biology of the Brain
The brain is probably the most complex structure in the known universe; complex enough to coordinate the fingers of a concert pianist or to create a three-dimensional landscape from light that falls on a two-dimensional retina. While it is the product of many millions of years of evolution, some of the structures unique to the human species have only appeared relatively recently.
Almost all the tasks that seem hard or difficult for human beings but that the present generation of computers can easily perform are associated with processing in parts of the relatively new cortex. Conversely, tasks that humans normally find easy but that are difficult for computers typically have a much longer evolutionary history.
In evolutionary terms, all brains are extensions of the spinal cord. The distant ancestor of the human brain originated in the primordial seas some 500,000,000 years ago. Life and survival in those seas was relatively simple and in consequence these early brains consisted of just a few hundred nerve cells.
A major change occurred when these early fish crawled out of the seas and onto the land. The enhanced difficulties of survival on land led to the creation of the "reptilian brain".
The next major addition occurred with the mammalian brain in which a new structure emerged - the cerebrum or forebrain along with its covering, the cortex. By now, the brain consisted of literally hundreds of millions of nerve cells organized into separate regions of the brain and associated with different tasks.
About 5,000,000 years ago, another type of cortex appeared in a new species - early man. In this brain, the surface of the cortex was organized into separate columnar regions less than one millimeter wide but each containing many millions of nerve cells or neurons. This new structure allowed much more complex processing to take place.
Finally, about 100,000 years ago, this new cortex underwent rapid expansion with the advent of modern man. The present day cortex contains something like two-thirds of all neurons and weighs about three pounds - almost triple its weight only one hundred thousand years ago!
Check out this gorgeous site!
http://www.phy.syr.edu/courses/modules/MM/brain/large/large.html
The brain is probably the most complex structure in the known universe; complex enough to coordinate the fingers of a concert pianist or to create a three-dimensional landscape from light that falls on a two-dimensional retina. While it is the product of many millions of years of evolution, some of the structures unique to the human species have only appeared relatively recently.
Almost all the tasks that seem hard or difficult for human beings but that the present generation of computers can easily perform are associated with processing in parts of the relatively new cortex. Conversely, tasks that humans normally find easy but that are difficult for computers typically have a much longer evolutionary history.
In evolutionary terms, all brains are extensions of the spinal cord. The distant ancestor of the human brain originated in the primordial seas some 500,000,000 years ago. Life and survival in those seas was relatively simple and in consequence these early brains consisted of just a few hundred nerve cells.
A major change occurred when these early fish crawled out of the seas and onto the land. The enhanced difficulties of survival on land led to the creation of the "reptilian brain".
The next major addition occurred with the mammalian brain in which a new structure emerged - the cerebrum or forebrain along with its covering, the cortex. By now, the brain consisted of literally hundreds of millions of nerve cells organized into separate regions of the brain and associated with different tasks.
About 5,000,000 years ago, another type of cortex appeared in a new species - early man. In this brain, the surface of the cortex was organized into separate columnar regions less than one millimeter wide but each containing many millions of nerve cells or neurons. This new structure allowed much more complex processing to take place.
Finally, about 100,000 years ago, this new cortex underwent rapid expansion with the advent of modern man. The present day cortex contains something like two-thirds of all neurons and weighs about three pounds - almost triple its weight only one hundred thousand years ago!
Check out this gorgeous site!
http://www.phy.syr.edu/courses/modules/MM/brain/large/large.html
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