New research suggests that as we form a memory, our brain labels it with a geotag—information about where the memory was formed—and that this information is called to mind again when we retrieve the memory. The process may explain why recalling an event may lead to recollections of other events that happened in the same location.
This fascinating insight is the result of research conducted on a small group of patients with epilepsy whose treatment involved having electrodes implanted in their brains in preparation for surgery. According to a report published in the Nov. 29, 2013 issue of the journal Science, the electrodes allowed researchers to observe and record the activity of individual brain cells in a key memory center called the hippocampus as study participants performed various tasks that involved memory formation and retrieval.
Participants in the study were asked to play a video game in which they familiarized themselves with various locations in a virtual town, and then delivered 13 unidentified packages to specific locations. Observing the brain activity of each participant, the researchers were able to identify specialized neurons, or place cells, that re-sponded to specific locations in the virtual town. When the participants had delivered the packages, they were told what items they had delivered (for example, shoes to the department store), and later asked to recall those items. The scientists observed that immediately before an item was recalled, the place cells associated with the location where the item was delivered became active. This geotagging process is thought to be one way the brain provides context to memories of events, situations, or experiences.
WHAT YOU CAN DO
The acronym GULP can help you remember key strategies for retaining and recalling information:
- G: Get it. Pay attention, focus, and experience new information with multiple senses.
- U: Use it. Repeat new information, review it immediately, write it down, draw it, say it, sing it.
- L: Link it. Associate what you want to learn with something you already know. Alphabetize it, categorize it.
- P: Picture it. Create a visual image. Exaggerate it—see a giant pill bottle by the door to remember to refill your prescription. The more actively you try to imagine what you want to recall, the better you will remem-ber.
“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.
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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