Memory crashes: Why does the brain confuse memories with age?
With age, a person can not only forget events, but also remember them less accurately: the brain begins to mix the details of different experiences with each other. This conclusion was reached by researchers who studied the brain activity of young, middle-aged and elderly participants during the formation and retrieval of memories. About why the brain can confuse events with age and what role the hippocampus plays in this, see the "Izvestia" material.
How memory works and why it can be wrong
Memory is not an accurate record of everything that happens to a person. Conventionally, the process can be divided into three stages: first, the brain perceives and encodes the details of the event, then stores the information, and later extracts it when a person needs to remember something.
For example, a person is talking to a friend. During a conversation, the brain captures what is happening, then saves the information received, and after a while, if necessary, it tries to restore this episode. It is at the extraction stage that an error may occur: a person remembers the event itself, but confuses individual details or their source.
Such memory distortion does not necessarily mean that the memory has completely disappeared. Information can be preserved, but it can be difficult for the brain to determine which event a particular detail relates to. As a result, the elements of several episodes may not be connected correctly.
Research shows that with age, the likelihood of certain types of false memories increases. For example, a paper published in the journal Psychology and Aging linked age differences in false memories to the processes of controlling and monitoring information during its retrieval.
Why do older people start mixing things up
To understand at what stage such errors occur, scientists studied the brain function of representatives of three age groups: young, middle-aged and elderly. The results of the study are published in the journal Cerebral Cortex.
During the experiment, participants were shown an image of a face at the top of the screen and an image of an object or scene at the bottom. Participants were asked to imagine that the person in the photo was interacting with an object or was in the scene shown. Each pair of images became a separate event that needed to be remembered.
After that, the participants rested for 20 minutes, while the researchers continued to record their brain activity. Then the memory test began: the person was shown a previously familiar face again, but four images were placed under it. It was necessary to determine which object or scene was originally associated with this person.
It turned out that older participants were more likely than younger ones to confuse the details of their memories. For example, they might recall that the face that was originally associated with the image of an apple was shown along with a forest. Thus, it wasn't just about completely forgetting the original event. A person could remember the face and the images themselves, but it was wrong to connect them together. It is precisely this substitution of one detail for another that has become one of the key results of the study.
What role does the hippocampus play?
The researchers separately studied the hippocampus, an area of the brain that is involved in various stages of working with memories. When an event is formed, a certain pattern of neural activity occurs in it. Similar patterns may appear later when the brain stores information and then extracts it again.
In young people, the repetition of such patterns is due to the fact that the brain activates the representation of a particular event again. Therefore, the researchers expected that with proper recall, brain activity would resemble that which occurred during the initial experience. In older participants who were more likely to confuse events, the researchers found a less pronounced repetition of the initial patterns of brain activity at different stages of working with memories. This was consistent with the assumption that as the brain ages, it becomes more difficult to reproduce accurate information about a particular event.
However, the results turned out to be more complicated than expected. Sometimes older participants still showed a repetition of the initial activity patterns, but even more often they made mistakes and mixed up memories. Therefore, the study does not come to the conclusion that the hippocampus simply starts to "work worse." The authors found evidence that as we age, this area of the brain can change memories between different stages of their processing.
At the same time, it remains unknown exactly what kind of brain activity helps an elderly person to correctly reconstruct an event. The researchers also could not determine whether other areas of the brain could compensate for changes in the hippocampus.
Why does the brain confuse the details of the past
The ability to correctly recall not only the information itself, but also its source has a special significance for memory. It can be important for a person to understand not just what he saw or heard, but where and when it happened. Modern research using functional MRI shows that several areas of the brain are responsible for monitoring the source of information, rather than one area.
For example, a meta-analysis of fMRI studies published in the journal Human Brain Mapping showed that source monitoring and so-called reality monitoring are associated with different, though partially overlapping, brain regions. This helps explain why a person can remember the detail itself, but be mistaken about its origin.
Age-related changes in this system can manifest themselves in different ways. A study published in the journal Memory & Cognition has shown that susceptibility to various types of false memories changes with age, but the different mechanisms of such errors are not necessarily related. The authors note that the occurrence of distortions can be influenced by different cognitive processes.
Therefore, age-related memory changes cannot be described only as a gradual erasure of the past. In some cases, the information remains, but the connections between its elements become less precise. A person can remember a conversation, a place, a person, or an object, but connecting these details is no longer the way they were connected in reality.
In a new study, scientists have yet to find out which areas of the brain help older people to correctly reconstruct events and whether they can compensate for changes in the hippocampus. In the future, researchers are considering ways to influence this area of the brain, but it is not yet known whether such an intervention will make memories more stable and consistent.
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