Fall 1996 Volume 5, Number 4
Schizophrenia was discussed by Donald Goff, M.D., Director of the Psychotic Disorders program in the Department of Psychiatry, at Massachusetts General Hospital, and Francine Benes, M.D., Ph.D., Director of the Laboratory of Structural Neuroscience at McLean Hospital. Spinal cord injury and motor neuron disease were discussed by Alfred Sandrock, M.D., Ph.D., and Robert Brown, M.D., Ph.D. of Massachusetts General Hospital. Introductory remarks were by Gerald D. Fischbach, M.D., Chairman of the Department of Neurobiology and Director of the Harvard Mahoney Neuroscience Institute.
DR. FISCHBACH: I want to welcome you to this Boston edition of
the Dialogues on the Brain. We have had sessions in the past on subjects such as chronic pain, depression,
Alzheimer's disease, and certain heritable disorders. Today, we've decided to
focus on two of the most important areas affecting our society. First,
schizophrenia, a thought disorder that touches many American families. Second,
we will discuss injury to the spinal cord --what has been learned, and what we
may expect in the near future.Now, I want to give you a brief primer in neurobiology, so that you can perhaps better follow the discussions.
We have learned a tremendous amount about the brain. For example, we can tell you that visual information passes from the eyes to the rear pole of the brain where is further processed. We can tell you where, once receiving sensory information like vision or auditory information, or taste, or olfaction, the brain becomes activated, and where decisions are made about movement.
With a beautiful MRI image of a real human brain, you can see an area lighting up that is responsible for sensation; we can see this now with imaging devices that actually detect activity through the intact human cranium. This is called a "non-invasive" way of examining the brain.
But what about everything between the input, the sensation, and the output, the movement --all that is so essential to human life, the thinking, the feeling and the moods and the emotions that we all experience? Well, we can't localize those yet. But we've learned a tremendous amount about the components of the brain that we feel will lead us to these sorts of answers.
If we were to look at a microscopic image inside that brain, you would see the components of the brain. The brain is made up of billions, 100 billion approximately, of nerve cells. If we stain nerve cells with dyes so that they become visible, you can see them with the naked eye, looking through a microscope.
They're tiny; don't be fooled by seeing a large image. The analogy I like to use is this: If a nerve cell were the size of a hair on your head, then the brain would have to be spread over almost half of Boston, if drawn to scale.
A neuron is a very busy cell; it communicates information from one cell to another. And they have so many and such complex interconnections between them, you can't really see or understand them on a microscopic image.
A nerve cell reaches out, through a long slender projection called an axon, to other cells and touches them at contacts known in the trade as synapses. These synapses transmit information from one cell to another. When sensations come in and a cell has received them, it must send the commands on to the next in line. It does so by transmitting information at each one of these small contacts.
The way it transmits information is by releasing chemicals at those contacts. At the edge of the cell, the membrane, chemicals are released to move across the distance between the cells, and interact with the "post synaptic" cell (the cell that's being "talked to"). We're going to hear a lot about those chemicals today.
I'm sure you've heard of some of them: Dopamine is one, norepinephrine is one, acetylcholine is another. You've probably heard of them because you know the names of drugs that affect them, by either increasing the release of the chemicals or preventing their interacting with the post-synaptic cell, or preventing their removal from the gap between the cells.
One of the drugs that can do this is cocaine, a commonly abused drug, that prevents the removal from the cleft --the "re-uptake" --of one of the transmitters, dopamine. Another is Cognex, one of our only, not very valuable, treatments for memory loss with advancing Alzheimer's disease. Cognex preserves another chemical, acetylcholine, in the synaptic cleft. A third is Prozac, one of the most revolutionary drugs of our time, which prevents the removal of still another small chemical, serotonin, from the cleft. Prozac has wide use in treatment of depression and various anxiety disorders. And we will hear about more drugs when we discuss schizophrenia and thought disorders.