Brain Bullet Points

Most people have seen pictures of the brain and know that brain damage can cause a wide range of problems from weak and paralyzed limbs to memory and speech problems, but the rest is a mystery. For many psychology students the very thought of learning about the brain-how it is structured and how it functions-is scary. After all, everyone knows it is the most complex system on earth, and perhaps even in the universe, so having to learn about it is asking too much of most of us. Even so, most people have a curiosity about the brain, and most people, by the time they have reached middle age, have known someone who has suffered from brain damage. They might have a parent or grandparent with dementia, a teenage son who has had a mild head injury, or a good friend who has epilepsy, multiple sclerosis or Parkinson's disease. If they are over 50 they begin to notice they sometimes struggle to find words, forget what they went into the kitchen for, and take longer to learn new tasks. Of course baby boomers with these problems don't have brain damage, but their brains are definitely on the decline!

So I thought I'd list a few facts about the human brain. Like all bullet points, these are simplified, but never-the-less they may give you a few hooks to hang further knowledge on.

1.The main part of the brain is like a walnut with two symmetrical halves, called cerebral hemispheres. Underneath the cerebral hemispheres is a smaller "walnut" called the cerebellum, and behind that is the brain stem that extends into the spinal cord.

2. Most of the behaviors and thinking tasks we worry about are located in the cerebral hemispheres.

3. Generally the two hemispheres work together. They communicate with each other across a thick fiber tract called the corpus callosum.

4. The LEFT hemisphere controls movement and sensation on the RIGHT side of the body and vice versa. So a stroke in the left hemisphere can cause weakness or numbness on the right side of the body.

5. Each hemisphere can be divided up into lobes. These are called the frontal, parietal, temporal and occipital lobes.

6. Sensations from the external world come into the three lobes at the back or posterior part of the brain. The occipital lobe at the very back is involved in vision, the parietal lobe in front of it is involved in spatial concepts and touch, and the temporal lobe below the parietal lobe is involved in hearing and memory.

7. The information that has been collected and analyzed by the lobes in the posterior part of the brain are sent forwards to the large frontal lobes in the anterior part of the brain. These frontal lobes then decide what to do with the information.

8. The frontal lobes are the most highly evolved part of the brain and allow us to think abstractly, act in ways that are appropriate and socially acceptable, work out problems in our head, and learn from our mistakes. They are also important to keep us alert and aroused. Unfortunately they are very vulnerable to damage, and can be damaged by head injuries, excessive alcohol and drug intake, and dementia.

9. The outer layer of nerve cells (neurons) on the hemispheres is called the gray matter, and the mass of nerve fibers (axons) that extend down into the hemisphere from each neuron is called the white matter.

10. Each neuron or group of neurons is related to a specific ability or function. Damage to the neurons will therefore damage those abilities. If the axons in the white matter are damaged, the neurons cannot communicate with one another and this can also cause problems.

11. Many abilities, like language or memory, are very complex and are mediated by a network of neurons working together. For example, if part of the language network is damaged, then the person may experience one sort of language problem and if another part is damaged they may experience a different sort of language problem.

12. In about 96% of right handers and 70% of left handers, the LEFT hemisphere is dominant for language function. This means that if you have a stroke that damages the left hemisphere you are more likely to suffer language and speech problems than if you have a stroke in your right hemisphere.

13. In most people the RIGHT hemisphere is better than the left hemisphere at spatial tasks like drawing.

14. There is no strong evidence that the right hemisphere is more creative than the left hemisphere. When painting a picture you probably use your right hemisphere more and when you are writing a story you probably use your left hemisphere more. When a non-musician is listening to music the right hemisphere is more involved but a musician uses both hemispheres when they listen to music. To some extent experience changes the way the brain works.