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News Gram™ October 2005

October 2005 ~ Volume 12, No. 3

Suppose you wanted to build your own brain. It’s not the craziest idea in the world. The problem is that the technology involved is pretty sophisticated, especially the part

having to do with living tissue. Artificial intelligence fiends work on building brains every day. They think it’s only a matter of time before they produce not just a brain, but a conscious, hard-wired, computerized something or other they will name Harrold or Izzy or Gallahad. For now, though, let’s see what parts are involved and how to put them together.

The brain works on the basis of its interconnectedness. The smallest components of it are the neurons and the glia, the latter being the support structure that holds the neurons together. There are billions of connections in the brain and we needn’t bother with them for now. Let’s just keep in mind that the wiring of the brain is the really hard part of this project.

Actually, we’re going to build a central nervous system, sometimes called the CNS. And let’s start with the spinal cord. This part of the CNS interacts directly with the peripheral nervous system, the network of nerves and their receptors in the skin and the organs of the body. The spinal cord receives sensory information from the surface of the body, the muscles, joints and trunk. The fibers from these areas go up the back of the cord into the brain itself. Also, the cord contains those fibers that start on the surface of the brain and course downward all the way to the muscles that move the body through space. Inside the body of the spinal cord are various nuclei, collections of neurons that help conduct nervous impulses through the cord and then out to the rest of the body. This model explains why severing the cord produces paralysis and also interrupts the transmission of sensory impulses to the brain.

Having put the cord in place as our first piece of the puzzle, we build on it by constructing a brain stem. This set of structures has little to do with consciousness or thinking but is responsible for controlling things to which we ordinarily give little or no thought. The medulla oblongata, which appears as a thickening of the spinal cord, is responsible for governing such processes as digestion, breathing and heart rate. Without the medulla, we would not live very long. Some of the cranial nerve nuclei, cell groups that control movement and sensation of the face are in the medulla. It is a very crowded structure that is always very busy.

Just above the medulla is the pons, which conducts information from the cerebral cortex to the cerebellum, which helps the body to balance itself in space. The way the cerebellum regulates the motion of the body is by helping to control the force and range of bodily movements. It also has a lot to do with the learning of motor skills.

On top of the brain stem is the midbrain, which helps control such things as eye movement and coordinate visual and auditory reflexes. Together, the three regions of the brain stem operate so smoothly that the higher centers of the brain do not have to ask themselves how many times a minute to take a breath or how fast the heart should beat. The brain stem makes it possible for philosophers to think and poets to wax eloquent.

Above the brain stem something called the diencephalons whose two main parts, the thalamus and the hypothalamus, deal with very different functions. The thalamus is a processing center for information that is traveling to higher levels of the brain. It organizes this information in such a way that the brain can make maximal use of it. The hypothalamus regulates autonomic, endocrine and visceral functions. Together, the two structures help maintain the internal milieu of the brain that is necessary if conscious activity is to take place.

Crowning this hierarchy are the cerebral hemispheres. These are the large, roundish crowns that take us to the highest level of brain function as well as location. To be continued…

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