We create countless memories as we live our lives, but many of them we forget. Why? Contrary to popular belief that memories simply decay over time, “forgetting” may not be a bad thing, according to scientists who believe it may represent a form of learning.
The scientists behind the new theory – featured today in a leading international journal Nature Reviews Neuroscience — propose that changes in our ability to access specific memories are due to environmental feedback and predictability. Rather than being an error, forgetting may be a functional feature of the brain, allowing it to dynamically interact with the environment.
In a changing world like the one in which we and many other organisms live, forgetting some memories can be beneficial as it can lead to more flexible behavior and better decision-making. When memories are gained in circumstances not entirely relevant to the current environment, forgetting can be a positive change that improves our well-being.
So scientists think we learn to forget some memories while retaining others that are important. Forgetting comes at the cost of lost information, of course, but a growing body of research suggests that forgetting, at least in some cases, is due to altered memory access rather than memory loss.
The new theory was developed by Dr. Tomás Ryan, Associate Professor at the School of Biochemistry and Immunology and the Trinity College Institute of Neuroscience at Trinity College Dublin, and Dr. Paul Frankland, a professor in the Department of Psychology at the University of Toronto and the Toronto Hospital for Sick Children, suggested.
Both Dr. Ryan as well as Dr. Frankland are fellows from the Canadian global research organization CIFAR, which made this collaboration possible through their Child & Brain Development program, which pursues interdisciplinary work in the field.
Dr. Ryan, whose research team is based at Trinity Biomedical Sciences Institute (TBSI), said:
“Memories are stored in ensembles of neurons called ‘engram cells,’ and successful retrieval of these memories involves reactivation of these ensembles. The logical extension of this is that forgetting occurs when engram cells cannot be reactivated. The memories themselves are still there, but if the specific ensembles cannot be activated, they cannot be retrieved. It’s like the memories are kept in a safe but you can’t remember the code to unlock it.
“Our new theory proposes that forgetting is due to the remodeling of circuitry that switches engram cells from an accessible to an inaccessible state. Because the rate of forgetting is influenced by environmental conditions, we propose that forgetting is actually a form of learning that alters the accessibility of memory in keeping with the environment and how predictable it is.”
Dr. Frankland added:
“There are several ways our brain forgets, but all act to make the engram — the physical embodiment of a memory — more difficult to access.”
Referring to the case of pathological forgetting in disease, Dr. Ryan and Dr. France:
“Importantly, we believe that this ‘natural forgetting’ is reversible under certain circumstances and that in disease states – such as those living with Alzheimer’s disease – these natural forgetting mechanisms are hijacked, resulting in a greatly reduced engram cell leads to accessibility and pathological memory loss.”
Materials provided by Trinity College Dublin. Note: Content can be edited for style and length.