It is not uncommon for people to forget the name of the person they just met or what they had for lunch. Forgetting information is a constant in life — it can be helpful for people who are coping with grief or need to let go of unapplicable knowledge. Now, scientists are beginning to examine the idea that lapses in memory are not bad at all, but rather could be a key part of how the brain supports learning. Tomás Ryan of Trinity College Dublin and his colleagues, recently began examining the fundamental biology behind “everyday forgetting” and how it plays an active role in the brain’s ability to obtain and retain information.
It is important to understand that there is a distinction between “everyday forgetting” and other forms of forgetting. Amnesia is a type of forgetting that many people would agree is not beneficial to human function. “Everyday forgetting” can be defined as when someone does not have at hand the desired memories for the situation.
In their study, Ryan tested “everyday forgetting” in rodents. He trained them to associate an object (like a tube) with the room that they were in. Then, over the course of a few days or weeks, the mice were reevaluated. The mice were placed in front of two objects; one that they had been trained to associate with the environment, and one that they had not. While one would expect that the mice would only explore the object they had never seen before, this was not the case. The mice had forgotten the association and begun to explore both objects the same.
In another study, Ryan and his colleagues studied fear conditioning, where the rodents received a mild shock for a few seconds. No harm came to the animals when the shock was delivered. They found later during the reevaluation that the mice displayed a “freezing” behavior when placed in the same environment, when they remembered the shock experience.
In an interview with Mind Matters editor Daisy Yuhas, Ryan was asked how these studies explained memory formation in the brain. He explained, “The brain is different before and after learning information. That difference is accounted for by physical or chemical changes in the brain’s structure. We call a brain change that occurs during learning and that is required for memory an engram”.
An engram, or a memory trace, has transformed the memory and forgetting fields over the last decade due to the ability to label and manipulate engrams in rodent brains. Engrams helped Ryan and his colleagues narrow down their research–they were able to look through billions of neurons and synapses in order to tag cells that were active while the rodent’s brains were forming memories during experiments.
Through the use of engram tags, the team was able to deduce that forgetting may be caused by competition between different memories. Therefore, forgetting is a form of learning and decision making because it forces the brain to decide with an engram to express in a given environment.
Tomás Ryan further explained that the memory loss, engram labeling, and learning can all be linked to trauma and dementia. When looking at amnesia and early Alzheimer’s in mice, the scientists found that they could stimulate the engrams of forgotten memories–causing the rodents to remember them.
This concept redefines dementia from a disease that causes memory loss to degraded engrams that trigger the natural process of forgetting too early in life. This could mean that memory loss could be reversible given the engrams are intact.
Ryan and his team continue to work with rodents to better determine how engrams can become the key to problems regarding memory loss and thinking in general.
