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Neurotransmitter

Neurotransmitters' Role In Memory And Learning

One of the most exciting areas of research is the attempt to find out how learning and memory take place. One of the earliest researchers who attempted to explain learning and memory as a function of cellular change was the Canadian psychologist, Donald O. Hebb. He maintained that repeated firing of axons results in metabolic changes in the presynaptic and post synaptic neurons. In other words, learning produces lasting chemical changes in nerve cells.

Aplysia, a marine snail with only 20,000 relatively large neurons, has been used in studies to determine the biological basis of learning. A conditioned reflex in Apylsia has been shown to cause an increase in the release of a neurotransmitter that sets up a chain of reactions, one of which also increases the secretion of serotonin from a modulating neuron. In mammals, the hippocampus, part of the forebrain, stores long term memory for weeks before transferring it to the cerebral cortex. The transmitter used for long term potentiation is the amino acid, glutamate, which binds to receptors in the postsynaptic cell. This cell allows calcium to flow in and set up the activation of other molecules known as kinases. A growing body of evidence implicates the role of dopamine as one of the most important chemicals that regulate cell activity involved in working memory. Studies done with aged monkeys show that a deficiency in both dopamine and norepinephrine in the prefrontal cortex can induce a deficit in working memory. Injections of the deficient neurotransmitters restored memory function. Progress in deciphering the operation of the nervous system has helped to increase knowledge of the diverse role of the neurotransmitter.

See also Chemoreception.

Resources

Books

BSCS Revision Team. Biological Science, A Molecular Approach. Lexington, MA: D.C. Heath & Co., 1990.

Campbell, Neil A. Biology. Menlo Park, CA: Benjamin/Cummings, 1987.

Campbell, N., J. Reece, and L. Mitchell. Biology. 5th ed. Menlo Park: Benjamin Cummings, Inc. 2000.

Carey, Joseph, ed. Brain Facts, A Primer on the Brain and the Nervous System. Washington, DC: Society for Neuroscience, 1993.

Holtzman, Eric, and Alex B. Novikoff. Cells and Organelles. Philadelphia: Saunders College Publishing, 1984.

Kuffler, Stephen W., and John G. Nicholls. From Neuron to Brain. Sunderland, MA: Sinauer Associates, 1976.

Purves, Dale. Body and Brain, A Trophic Theory of Neural Connections. Cambridge, MA: Harvard University Press, 1988.

Raven, Peter H., and George B. Johnson. Biology. 3rd ed. St. Louis: Mosby Year Book, 1992.


Periodicals

Fischbach, Gerald D. "Mind and Brain." Scientific American 3 (1992): 48-57.

Golden, Frederic. "Mental Illness: Probing the Chemistry of the Brain." Time 157 (January 2001).

Goldman-Rakic, Patricia S. "Working Memory and the Mind." Scientific American 3 (1992): 110-117.

LeDoux, Joseph E. "Emotion, Memory, and the Brain." Scientific American 6 (1994): 50-57.


Mary Finley

KEY TERMS

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Action potential

—A transient change in the electrical potential across a membrane which results in the generation of a nerve impulse.

Axon

—The threadlike projection of a neuron that carries an impulse away from the cell body of the neuron.

Catecholamine

—Monoamines such as the neurotransmitters norepinephrine, serotonin, and dopamine that are synthesized from the amino acid, tyrosine, and have similar structures.

Conditioned reflex

—A response in which one stimulus, the conditioned one, is associated with and elicits the same response as another stimulus, the unconditioned stimulus.

Dendrites

—Branched structures of nerve cell bodies which receive impulses from axons and carry them to the nerve cell body.

Limbic system

—Group of nuclei in the lower part of the forebrain involved in certain emotional and behavioral responses.

Monamine oxidase

—An enzyme found in the brain and liver which breaks down catecholamines such as norepinephrine, serotonin and dopamine.

Synapse

—Junction between cells where the exchange of electrical or chemical information takes place.

Working memory

—Memory that accesses and brings to mind information stored in longterm memory.

Additional topics

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