The Brain: A Primer

By J. Mark Bade

September, 2010

If you’re in the 2e community, chances are good that you know someone with dyslexia (or maybe you’re dyslexic). When a dyslexic reads, the regions of the brain that are active are different than they are in other people.

In people with generalized anxiety disorder, connections between one part of the brain, the amygdala, and other parts are apparently different, “scrambled,” in the words of some researchers.

And that bright child you know with AD/HD? Not only might certain parts of that child’s brain be smaller and less active, the brain might show reduced levels of dopamine, a chemical used by brain cells to communicate.

Over the past decade or so, there’s been an explosion of understanding of the brain based on functional magnetic resonance imaging (fMRI) and other research techniques. Much of that understanding relates directly to the most common second exceptionalities – learning challenges – in twice-exceptional children. In this article, we’ll cover some basics of brain structure and function. Later articles in this series will cover how the brain works – or doesn’t work – in some of the common exceptionalities found in 2e kids.

Overall Structure

The three-pound organ under our hats and between our ears, the one that puts us so smugly atop the animal kingdom, has three main parts – the hindbrain, midbrain, and forebrain. Looking at a cross-section of the brain, the hindbrain is at the lower right, connected to the spinal cord. Two parts of the hindbrain, the pons and the medulla oblongata, control autonomic functions – bodily functions such as breathing and heartbeat. Another part of the hindbrain, the cerebellum, helps coordinate and control certain movements, especially the learned movements involved in sports or playing a musical instrument. 

The midbrain, above the hindbrain, consists of a group of nerve cells called nuclei. This part of the brain is involved in reflex actions and carries signals for voluntary movement. Part of the midbrain is responsible for transmitting sensory information to other parts of the brain.

The forebrain is a collection of structures with functions ranging from high-order thought to basic chemical control of the body via hormones. The outside of the forebrain is the cerebrum, home of intellect, memory, planning, imagination, and thought. The cerebrum has two hemispheres, left and right, connected by a set of nerve fibers called the corpus callosum. Contrary to popular thought, the functions of the cerebrum are not divided symmetrically, and it’s overly simplistic to think of the right side of the brain as creative and the left side as analytical. Most of time we use the entire brain, and information travels back and forth between the two hemispheres.

The cerebrum hides some forebrain structures called “the inner brain.” These parts of the brain come in left-and-right pairs, like the cerebrum.

  • The thalamus structures relay information from the spinal cord to the cerebrum.
  • The hypothalamus performs regulatory functions for the body – like temperature control – and uses the pituitary gland in the brain to help carry out some of those functions; it’s also a locus for the control of emotion.
  • The amygdala controls the way other brain areas respond to emotions such as fear or aggression, for example fleeing in response to a certain stimulus.
  • The hippocampus coordinates memory storage and retrieval.

A layer of gray nerve tissue, called the cerebral cortex, covers the outside of the cerebrum. This layer shows the convolutions we associate with the exterior of the brain.

The forebrain has a number of lobes on its surface; these pairs of lobes are home to various control and input/output functions.

  • The frontal lobes are involved in planning and imagination, as well as in other functions, including motor activity.
  • The parietal lobes handle sensory information but also play a part in functions such as reading and math.
  • The occipital lobes’ main function is vision, receiving and processing information from the eyes.
  • The temporal lobes process smell and sound, but also have a role in memory formation.

Brain Connections

The information the brain transmits and processes is carried by neurons. Our brains may hold as many as 100 billion neurons. While that number is not impressive compared to the national debt, it compares favorably with storage capacity in modern computing devices. Each neuron contains:

  • A cell body with a nucleus
  • Dendrites extending out from the cell body to receive information from other neurons
  • An axon to transmit electrical impulses away from the cell body to another neuron or to other types of cells such as muscles.
  • A myelin sheath to insulate the cell and speed signals.

The actual neuron-to-neuron communication is accomplished by chemical neurotransmitters moving across the synapse, the space between neurons. At the end of an axon, a nerve cell releases a neurotransmitter such as serotonin. The chemical molecules then cross the synapse, seeking receptors on the next cell that are specific to those chemical molecules. When they find the proper receptors, the chemical molecules bind to them. If this activity takes place in the brain, the receptors most likely will be on another neuron rather than, say, a muscle cell; and that neuron will move the signal along its journey from the originating neuron.

Some neurotransmitters are especially relevant to the world of 2e. These are:

  • GABA (gamma-aminobutyric acid). Some children with AD/HD have low levels of this chemical, which has an inhibitory function.
  • Dopamine. An abnormal level of this chemical is associated with AD/HD.  Drugs like Ritalin affect the level of dopamine in the brain.
  • Serotonin. This chemical is involved in mood and, in cases of depression, it may be controlled by drugs such as selective serotonin reuptake inhibitors (SSRIs).

Neurotransmitters are just part of the communication process in the brain. A  variety of mechanisms play a part, including hormones and even gasses. These other mechanisms are beyond the scope of this article, but may be covered in future articles.  

Brain Accessories

The brain comes with a set of accessories, for example a nice case, the skull, to enclose and buffer it. Additional cushioning comes from cerebrospinal fluid inside the skull. (Note that the exterior of the skull is user-customizable to provide a variety of looks and styles.)

The brain is powered by glucose, a form of sugar. The brain uses about 400 calories’ worth of glucose per day, perhaps 20 percent of an adult’s regular daily input of 2,000 calories. An extensive set of arteries in the brain transports glucose as well as oxygen.

The brain’s interfaces with the rest of the body include the optic nerves, along with sets of nerves for each of the other major senses, each entering through specially designed ports in the skull. The brain also features “fly by wire” connections (where control signals are sent over nerves) to the muscles of the body for locomotion and other actions; most of these are enclosed in the spine.

In addition, the skull encloses three glands critical to human functioning:

  • The pituitary gland, mentioned earlier, which produces eight hormones
  • The pineal gland, important for the sleep cycle
  • The hypothalamus, which, while not technically a gland, does secrete hormones and other chemicals that interplay with the endocrine (glandular) system.

Conclusion

The brain is a wonderful device, and we probably abuse it too much with chemicals, mishandling, and meaningless input like reality shows. An understanding of it helps mightily in dealing with professionals and literature as we seek to understand and support our twice-exceptional children. Future articles will build on the content of this article to cover the brain’s role in conditions such as AD/HD, Asperger’s, dyslexia, anxiety, and processing disorders.

This article is based on “Know Your Brain,” from the National Institute of Neurological Disorders and Stroke; “Brain Facts” from the Society for Neuroscience; the book The Human Brain, by Rita Carter; and other sources. Thanks to our friend John Schafer, M.D., Fellow of the American Academy of Neurology, who reviewed the article for accuracy, offering suggestions for improvement as well as proclaiming it “oversimplified” from a neurologist’s viewpoint; but that’s okay, ‘coz it ain’t that simple to the rest us.   

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