Stage Three Retrieval - How We Remember: Improving Memory Understanding Age Related Memory Loss

Content provided by the Faculty of the Harvard Medical School

Stage three: Retrieval

Retrieval is the act of recalling something. A memory is stored in the brain as a unique pattern of nerve cell activation. When you're not thinking about the memory, its neuronal pattern is inactive. To retrieve the information, your brain must reactivate the pattern. Similar memories have partially overlapping patterns of neuronal activation. Sometimes when you try to retrieve one bit of information, a similar memory comes to mind and blocks out the information you want. For example, you may be trying to recall the name of Jim Carrey's first movie, but instead you keep thinking of the name of his most recent film.

Researchers have determined how long it takes to reactivate a neuronal pathway holding simple, familiar information — less than a second. They've found, for example, that when someone sees a photograph and is asked whether it's familiar, it takes about a fifth of a second for the image to reach the visual system in the brain, a fifth of a second for the person to decide whether it's familiar, and another fifth of a second for the person to reply.

If it always took just a fraction of a second to remember something, you wouldn't worry about your memory. But, of course, it often takes considerably longer. Even if your memory is perfect, it can take several seconds or more to recall complicated information. How long the process takes depends on how familiar you are with the information you're looking for. If someone asks you to name the third president of the United States, for example, and you're an American history teacher, you may be able to recall in an instant that the answer is Thomas Jefferson. Otherwise, your brain will activate neuronal pathways that encode information related to the chronology of the presidents — the year when the United States was founded and the names of any early presidents that come to mind, for instance. In the process, you may feel that the answer is "on the tip of your tongue." If the neuronal pathway in your brain leading to the answer is still intact, you'll eventually retrieve it.

Last updated:	January 23, 2007