Why Do We Forget?

Not being sure if you locked the door on the way to work or school, or not being able to recall the lyrics of a song you once knew by heart… We all face such situations, don’t we? We all forget things from time to time. But why do we forget and what lies behind it? Why can’t we remember everything? Is there a way to bring back forgotten memories? Seeking answers to these questions, researchers from the Institute of Biochemistry and Immunology and the Institute of Neurobiology at Trinity College Dublin offer a different perspective on the nature of forgetting with their study on mice, the results of which are published in Cell Reports. The study shows that forgotten memories can be reactivated and even altered, deepening our understanding of the nature of the forgetting, the reasons why we forget and the process of “remembering”.

Our brain operates inside a complex network of billions of neurons. The interplay between these neurons shapes our ability to remember and the experiences we have throughout life. But perhaps the most interesting part of this dance is the relationship between memory and forgetting. Recent research shows that forgetting is not just lack of memory, but an indicator of the brain’s ability to adapt and process new information. It also reveals that forgetting is an active process. Therefore, taking a closer look at this mysterious relationship between memory traces and forgetting could be an important step towards unveiling the mysterious ways of the brain.

An “engram” is a pattern of neuronal activation that represents the neural traces of memory. When we recall a memory or perform a skill, the memory traces (engrams) associated with that particular memory are activated.

Have you ever wondered how new information affects our present vault of information when we learn something? This is where a process called “retroactive interference” comes into play. This process shows that the new bits of knowledge we acquire may confuse our previous knowledge, and sometimes even make us forget the old ones.  But it is important to point out that forgetting is not a one-way street. Another process, called “proactive intervention”, may help us recall previous knowledge, and remember things.

Research shows that forgetting occurs as a result of various different memory traces competing with each other. When we learn a lot about a specific topic, all that information gets in a competition, some of it getting pushed to the background as a result. This is one of the types of forgetting we often encounter in everyday life.

Findings from marking memory traces and a technique called optogenetics prove that even when we forget something, those memories still remain in our brains. So, forgetting does not mean information being erased. These findings show that forgetting is an active process of our brain and that memory traces are still there somewhere.

So how can you revive dormant memories? The study contains a lot of technical terms, but it boils down to this: Re-exposure to what you have already learned, for a short period of time. For example, you are trying to learn a language and you finish one chapter. Before moving on the next day, spend a few minutes reviewing what you learned yesterday. In short, updating your memory involves your brain forgetting some information in a strategic way. You may need to discard old information while learning new things. But they are not completely erased. Research shows that “forgotten” memories simply lie dormant and can be recalled when needed. Therefore, it is often easy to remember because the information is still there somewhere.

These findings suggest that memory is a flexible and dynamic process, and that forgetting is not just a lack of knowledge, but an indicator of the ability to process new information.

The relationship between engrams and forgetting is one of the most exciting and mysterious topics in neuroscience. A better understanding of these processes could open new avenues for tackling problems related to human memory and mental health. Thus, a deeper study on engrams and forgetting could be an important step towards unravelling the mysteries of the brain and the human mind.