Forgetting May Be a Form of Learning, Study Finds
Author: Trinity College Dublin
Published: 2023/08/18 - Updated: 2026/02/19
Publication Details: Peer-Reviewed, Findings
Category Topic: Human Brain - Related Publications
Contents: Synopsis - Introduction - Main - Insights, Updates
Synopsis: This peer-reviewed research, published in the leading international journal Cell Reports, presents the first experimental evidence supporting the theory that forgetting is not a flaw in memory but a functional feature of the brain. Led by Dr. Tomas Ryan at Trinity College Dublin, the study used genetic labeling and optogenetics in mice to show that so-called forgotten memories are not erased - they remain stored in groups of brain cells known as engram cells but simply become inaccessible, much like a safe whose combination has been temporarily lost. The researchers demonstrated that these hidden memories could be reactivated using both light stimulation and natural environmental cues, and could even be updated with new information. This work carries serious implications for people living with Alzheimer's disease and other forms of dementia, where everyday forgetting processes may be abnormally triggered by brain disease, and it offers a new way of thinking about memory loss that is directly relevant to seniors, caregivers, and anyone affected by cognitive disabilities - Disabled World (DW).
- Definition: Forgetting (Neuroscience)
Forgetting, in the context of neuroscience, is the inability to retrieve information that was previously encoded and stored in the brain. Traditionally viewed as a failure or weakness of the memory system, recent research has begun to redefine forgetting as a potentially adaptive process - one in which the brain deliberately reduces access to certain memories in order to prioritize more relevant or current information. This process appears to be governed by competition between memory traces known as engrams, where newer experiences can interfere with the retrieval of older ones without actually erasing them. The distinction is critical: the memories themselves may remain physically intact within neural circuits, but the pathways needed to access them become suppressed. Understanding forgetting in this way has significant implications for conditions such as Alzheimer's disease, traumatic brain injury, and age-related cognitive decline, where disruptions to normal forgetting processes may contribute to the memory difficulties that patients and their families experience daily.
Introduction
Forgetting Is Actually a Form of Learning
"Adaptive Expression of Engrams by Retroactive Interference" - Cell Reports.
Neuroscientists report the first results from experimental tests designed to explore the idea that "forgetting" might not be a bad thing, and that it may represent a form of learning - and outline results that support their core idea.
Main Content
Last year the neuroscientists behind the new theory suggested that changes in our ability to access specific memories are based on environmental feedback and predictability. And that rather than being a bug, forgetting may be a functional feature of the brain, allowing it to interact dynamically with a dynamic environment.
In a changing world like the one we and many other organisms live in, forgetting some memories would be beneficial, they reasoned, as this can lead to more flexible behavior and better decision-making. If memories were gained in circumstances that are not wholly relevant to the current environment, forgetting them could be a positive change that improves our wellbeing.
Today, in leading international journal Cell Reports, they present the first in a series of new experimental studies where the effect of natural, "every day" forgetting was investigated with respect to how normal forgetting processes affect particular memories in the brain.
The team studied a form of forgetting called retroactive interference, where different experiences occurring closely in time can cause the forgetting of recently formed memories. In their study, mice were asked to associate a specific object with a particular context or room, and then recognize that an object that was displaced from its original context. However, mice forget these associations when competing experiences are allowed to 'interfere' with the first memory.
To study the result of this form of forgetting on memory itself, the neuroscientists genetically labelled a contextual "engram" (a group of brain cells that store a specific memory) in the brains of these mice, and followed the activation and functioning of these cells after forgetting had happened.
Crucially, using a technique called optogenetics they found that stimulation of the engram cells with light retrieved the apparently lost memories in more than one behavioral situation. Furthermore, when the mice were given new experiences that related to the forgotten memories, the 'lost' engrams could be naturally rejuvenated.
Dr Tomás Ryan, Associate Professor in the School of Biochemistry and Immunology and the Trinity College Institute of Neuroscience at Trinity College Dublin, is lead author of the just-published journal article.
Dr Ryan, whose research team is based in the Trinity Biomedical Sciences Institute (TBSI), said:
"Memories are stored in ensembles of neurons called 'engram cells' and successful recall of these memories involves the reactivation of these ensembles. By logical extension, forgetting occurs when engram cells cannot be reactivated. However, it is increasingly becoming clear that the memories themselves are still there, but the specific ensembles are not activated and so the memory is not recalled. It's as if the memories are stored in a safe but you can't remember the code to unlock it."
Dr Livia Autore, Irish Research Council (IRC) Postgraduate Scholar, who spearheaded this work in the Ryan Lab in Trinity, added:
"Our findings here support the idea that competition between engrams affects recall and that the forgotten memory trace can be reactivated by both natural and artificial cues as well as updated with new information. The continuous flow of environmental changes leads to the encoding of multiple engrams that compete for their consolidation and expression."
"So while some may persist undisturbed, some will be subjected to interference by new incoming and prevailing information. However, the interfered memories can still be reactivated by surrounding cues leading to memory expression or by misleading or novel experiences ending up in an updated behavioral outcome."
Because we now know that "natural forgetting" is reversible in certain circumstances, this work has significant implications for disease states - such as in people living with Alzheimer's disease for example, where these every day forgetting processes may be mistakenly activated by brain disease.
Insights, Analysis, and Developments
Editorial Note: What sets this Trinity College Dublin research apart is that it does not simply describe forgetting as something that happens to us - it reframes it as something the brain does on purpose to help us function in a world that is constantly changing. The idea that forgotten memories still exist intact within engram cells, waiting to be unlocked by the right cue, challenges long-held assumptions about how memory loss works and opens a genuinely new line of inquiry for neurodegenerative disease research. If Alzheimer's and similar conditions are partly hijacking the brain's natural forgetting mechanisms rather than destroying memories outright, then therapies aimed at reactivating those dormant engrams rather than preventing their loss could represent a fundamentally different approach to treatment - one that may prove far more achievable than trying to stop neurodegeneration itself - Disabled World (DW).Attribution/Source(s): This peer reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by Trinity College Dublin and published on 2023/08/18, this content may have been edited for style, clarity, or brevity.