How the Brain Remembers

“Studies such as this one help increase our understanding of how memories are formed and retrieved,” says Maurizio Fava, MD, Executive Vice Chair of the Department of Psychiatry at MGH. “The researchers were able to find neural evidence that helps explain why, when people think back to an event in their lives, they remember not only the event, but also where that event happened. This is another ex-ample of the amazingly complex processes that are involved in memory functioning. The more we understand these processes, the better able we will be to protect and enhance memory performance at all ages.”

The memory process

Memory formation is a restructuring of the brain. As new information is relayed to brain cells through the senses, a memory trace is transmitted by neurons across communication points called synapses to other neurons, forming new connections. The information is distributed among regions of the brain associated with sight, hearing, taste, smell, or feeling. From there a second set of neurons relays the memory trace via the brain’s temporal lobe to the hippocampus.

The hippocampus may hold the memory trace briefly in short-term memory (also called working memory), as when you keep a telephone number in mind briefly while you dial it. The information may be dis-carded or sent on for storage in long-term memory. If the information is committed to memory, the hippocampus processes the signal and sends it to the cerebral cortex, where it is put into long-term storage. Once it is lodged in the cerebral cortex, the memory trace is available for retrieval days, months and years later. Even in old age, healthy individuals retain the ability to form new long-term memories.

Memory retrieval occurs through the processes of recall and recognition. Recall requires the di-rect accessing of memories, as when you try to name the third president of the U.S., or remember a French vo-cabulary word. Recognition requires you to retrieve previously learned information by recognizing and selecting it from a group, as in a multiple-choice test.

The ability to recognize information is much stronger than the ability to recall it. But using external stimuli (retrieval cues) that are encoded at the same time a memory is formed can significantly improve re-call. Some cues can be created deliberately, such as using a rhyme or an alphabetical list to help fix something in your memory. Others are associations formed at the time a memory is encoded, such as the geotag. Still other cues may be related to the mood or mental state you experienced while encoding a memory.

Aging memory

Remembering unfolds in three stages—encoding (creating a temporary memory trace), consolidation (strengthening the initial trace so that you can store the information over time), and retrieval (calling up information). Healthy older adults often have the most problems with encoding and retrieving information. Both of these processes require focused attention and using strategies to organize and understand information, which can be a challenge for some seniors.

“Aging changes the brain in a number of ways, but you can adjust to these changes to minimize the impact on your memory performance,” Dr. Fava says. “Research suggests that older people who have learned cues or strategies to facilitate memory process have been found to have memory ability compara-ble to that of younger individuals. (See What You Can Do, Page 6.)

“Becoming more actively involved in the memory process—by, for instance, paying attention, forming mental pictures, or repeating information out loud—can help you improve your ability to organize and encode information ‘up front’ so you can recall it more easily later.”

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