Memory editing for mental health – Part 1: The curious world of memory reconsolidation
Deep dive by Conor D’Andrade
Even with millions of years of evolution on its side, the human brain can still be duped from time to time. One area that can be particularly affected is in the creation and management of memories which is central to many cases of mental health issues, from post-traumatic stress disorder to substance abuse. In the first of three articles on the subject, Conor D’Andrade delves into how we form memories in the first place and the science behind the mysterious process of memory reconsolidation.
My jaw has only dropped twice in my lifetime. The first, was when I was hit with the shock and horror of Game of Throne’s ‘Red wedding’ scene. The second, and the reason I am writing this now, was in a second-year cognitive psychology lecture on memory reconsolidation. Please bear in mind, I loved studying for my degree, I regularly enjoyed learning about a range of topics across modules, but that lecture was the one moment, across three years of study, I can say my mind was genuinely blown by what I was learning.
Just like I wouldn’t want to give any spoilers for Game of Thrones, I don’t want to reveal too early what fascinated me so much in this lecture. What I will say is that what I learnt in that lecture inspired me, almost profoundly, as a student, mostly because I was left wondering how memory reconsolidation, and its potential for treating mental health conditions, has been left out of main-stream knowledge for so long.
Before we get into the details…
The easiest way to understand memory reconsolidation is to first understand memory consolidation, which is actually a lot simpler than its name suggests.
Memory consolidation is a process our brain uses every day to help us remember important and potentially life-saving information. Specifically, it is the process of turning information we gather from our life experiences into long-term memories.
First proposed around 1900 by German psychologist Georg Elias Müller and his student, Alfons Pilzecker, our understanding of this process has expanded greatly in the 121 years since. Recent research has even been able to identify specific parts of the brain and their roles in the process.
Some of the major areas of the brain involved in memory consolidation. Source: University of Queensland, Australia. Where are memories stored in the brain?
Two of those areas of the brain that are very important in the process are the hippocampus and the neocortex. According to the research, the hippocampus acts as a kind of temporary storage unit for recent experiences – in other words, our short-term memory – allowing us to access that information for a short period before it fades. Simultaneously, that information is also being stored throughout the neocortex so that we can recall it in the future – in other words, our long-term memory.
The process is similar to how a computer uses RAM to store current information, and a hard drive to store that information permanently. But rather than information being stored in one part of the brain and then another, it’s actually making an impression on both areas of the brain simultaneously.
Neurones that fire together wire together!
Another similarity the process shares with computers is that much of the process can be considered in a ‘binary’ fashion.
If you’re unaware of the binary system, it’s a type of mathematical expression which only uses two symbols. For a computer, those two symbols are ‘0’ or ‘1’. Every file that is stored on a computer is made up of sequences of these two symbols, for example, a photo could be stored as 01010001011101101101.
Memories are stored in the brain in a similar fashion, but instead of using 0s and 1s, they are stored as sequences of ‘active’ or ‘inactive’ cells. Called neurones, these cells are highly specific and specialised, meaning they only activate in response to a specific thing or condition. If that specific thing or condition isn’t present, they are inactive. A memory is effectively a pattern of active and inactive neurones.
Examples of how files are stored in computers as binary code. Source: BBC Bitesize. Binary.
Still with me? Good, because this is where things get interesting.
As neurones become active (‘fire’) throughout the neocortex, they form networks with each other (hence “neurones that fire together wire together!”) These interactions can actually be observed in a lab at the cellular level, where a neurone that repeatedly fires causes physical changes in another neurone.
To be specific, the synaptic knob (imagine this as the 'tail' end) of the activated neurone enlarges and increases its contact area with the dendrites (imagine this as the 'head' end) of the next neurone. The relationship between the cells is quite literally getting stronger, which is the physical embodiment of what memory consolidation is.
How memories are formed between activated neurones.
Preserving and updating our memories
Now that we have some understanding of how a memory is formed, we can focus on the star of the show: reconsolidation.
As the name suggests, reconsolidation describes the process of a previously consolidated memory being consolidated again after it has been recalled.
This process serves two very important functions. The first is that it helps prevent memory decay, which can eventually lead to us forgetting a memory entirely. Reconsolidation stops this from happening by restabilising a memory for storage after each time it is recalled.
Secondly, memory reconsolidation is crucial for letting us update our memories which, although that might not sound like much, is likely to have been crucial in the survival of our species and others.
Explaining this is easiest using an example scenario:
One day, an early human is out hunting, when in the distance they see a dangerous predator that they want to avoid. Later in the day the hunter finds and studies tracks the predator has left. The visual memory of this predator and its tracks are consolidated in the hunter’s brain after some time passes.
A month later, the hunter is out hunting again, when suddenly they smell a large animal nearby. The hunter hears the animal quickly run away. When the hunter approaches the position the sound came from, they discover the same prints they saw a month ago. This causes the reactivation of the visual memory of seeing the predator a month ago. But, rather than reconsolidating this older visual memory and consolidating the new smell memory separately, the smell information is added to the original visual memory from a month ago through reconsolidation.
When the hunter smells the predator again in future, they knows they are in danger and need to hide, without having to literally see the danger.
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An editable process
So why is all this relevant to mental health?
Well, one of the most interesting characteristics of the reconsolidation process is that it allows for memories to be altered.
Going back to our two friends Müller and Pilzecker, their theory of memory consolidation actually came from the finding that newly learned information is vulnerable to interference for a short time after learning.
In order to do so, the process for reconsolidation must first be kickstarted which, according to a number of studies, only happens when an individual experiences something called ‘prediction error.’
Prediction error describes the mismatch between an expectation and an experience. It can either be positive – when something is expected to occur, and it doesn’t – or negative – when something isn’t expected to occur, and it does.
Whichever type of prediction error occurs always results in the need for a memory to be reconsolidated as it indicates that new information needs to be added to the recalled memory.
Taking our hunter example, if they were to hear the breathing of what they think is prey and is therefore something they can hunt, when they see that the animal is actually a predator, the prediction error indicates the need to update the memories associated with the predator. This means that in the future, the same mistake is not made.
Now take an example of a mental health issue, whether that’s depression, obsessive compulsive disorder, or even substance abuse. In many cases, memories can be key drivers in the development of these illnesses and can determine how symptoms manifest throughout someone’s lifetime. But, armed with the knowledge that memories can be recalled and amended, just imagine the positive impact reconsolidation could have…
In part two…
Conor D’Andrade delves deeper into the science behind memory reconsolidation and looks at ways we can influence the process.
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