Memory and Synaptic Plasticity

You may have wondered as you studied this chapter, How am I going to remember all of this? It seems fitting that we end this chapter with the subject of how memory works, for you now have the information necessary to understand its cellular and chemical basis.

The things we learn and remember are not stored in individual "memory cells" in the brain. We do not have a neuron assigned to remember our phone number and another assigned to remember our mother's birthday, for example. Instead, the physical basis of a memory is a pathway through the brain called a memory trace (engram27), in which new synapses have formed or existing synapses have been modified to make transmission easier. In other words, synapses are not fixed for life; in response to experience, they can be added, taken away, or modified to make transmission easier or harder. This ability of synapses to change is called synaptic plasticity.

Think about when you learned as a child to tie your shoes. The procedure was very slow, confusing, and laborious at first, but eventually it became so easy you could do it with little thought—like a motor program playing out in your brain without requiring your conscious attention. It became easier to do because the synapses in a certain pathway were modified to allow signals to travel more easily across them than across "untrained" synapses. The process of making transmission easier is called synaptic potentiation (one form of synaptic plasticity).

Neuroscientists still argue about how to classify the various forms of memory, but three kinds often recognized are immediate memory, short-term memory, and long-term memory. We also know of different modes of synaptic en = inner + gram = mark, trace, record

Saladin: Anatomy & I 12. Nervous Tissue I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

474 Part Three Integration and Control

ro potentiation that last from just a few seconds to a lifetime, and we can correlate these at least tentatively with different forms of memory.

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Essentials of Human Physiology

Essentials of Human Physiology

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