Study Reveals How the Brain Chooses Lasting Memories

The Memory Tagging Mechanism | The Memory Test | How are Memories Made? | What's the Takeaway?

Overview

Experts have long acknowledged the vital role of sleep in memory consolidation. During sleep, the brain processes the day’s events and stores them as memories.

However, we only sometimes recall everything we have experienced, implying that the brain picks specific events to store in long-term memory.

How the brain chooses the memories to keep has long puzzled experts.[1] Thankfully, a remarkable study from NYU School of Medicine explains how the brain selects the memories that will stay.

The Memory Tagging Mechanism

In a brilliant study published in Science Journal, experts from NYU Grossman School of Medicine explain how the brain marks specific memories to maintain them permanently.[2]

The researchers reasoned that “sharp-wave ripples” on a brain electrical tracing (EEG) produced after the brain experiences certain new events are the bookmarking mechanism that tags memories worth remembering.

Furthermore, they believed that significant events during the day would likely provoke more sharp-wave ripples on brain tracing.

This signal tells the brain to revisit those patterns during sleep and repeat them several times, etching the events into long-term memory.

The Memory Test

The researchers validated their hypothesis by putting mice through a series of maze tests.

Initially, they devised a method to detect brain wave data corresponding to the characteristic physical features of various maze sections. This method enabled the researchers to correlate brain wave patterns with certain trials as the mice successfully traversed the maze.

The sharp wave ripples were frequently noticed whenever the mice came across sugary treats as they maneuvered through the labyrinth. Also, shortened versions of these sharp-wave ripples were seen while the mice rested after enjoying their treats and frequently while they slept.

According to the study’s authors, the more sharp-wave ripples there are after an incident, the more probable the pattern will be reproduced throughout sleep, making the memory of the event last.

Conversely, any event that doesn’t generate sufficient sharp-wave ripples will likely be forgotten.

Dr. György Buzsáki, the study’s lead author, explained that memory consolidation while sleeping is extremely intricate and involves several brain wave patterns and sleep stages.[3]

He goes on to explain that the discovery of a link between the sharp-wave ripples produced during sleep and wakefulness sheds light on part of the memory puzzle and highlights the vital role quality sleep plays in preserving memories.^[2]

How are Memories Made?

The brain’s process for making memories is exceptionally complex and fascinating. One easy way to explain it is that memories are made in stages in the brain. These stages include:^[4]

1) Information Encoding

The initial step in memory creation is encoding. It is the change of information from the environment (what we perceive via our five senses) into a format that can be stored in the brain.

The “brain storage codes” are synaptic connections between brain cells (neurons). So, when a person perceives or learns something, the brain transforms that information into synaptic connections.

2) Storage

Once the brain stores the information it receives as synaptic connections, it attempts to retain it. Memory storage refers to the process of preserving synaptic connections.

The synaptic circuits are strengthened or weakened depending on how frequently we are exposed to the initial event. For example, repeatedly dunking a basketball will result in stronger and more durable synaptic connections. This finding means that even if you don’t play basketball for a long time, you’ll remember how to dunk when you pick it up again.

3) Consolidation

Memories become strengthened and more permanently preserved during consolidation. Deep sleep is particularly crucial to this process.

4) Retrieval

This step is when the brain recovers stored information. A memory cue usually triggers it. For instance, hearing someone call out a name could make you recollect experiences with someone with the same name.

What’s the Takeaway?

The NYU School of Medicine study sheds light on the brain’s intricate process of memory selection, emphasizing the critical role of sharp-wave ripples in tagging significant events for long-term retention.

This discovery enhances our understanding of how memories are consolidated during sleep and underscores the importance of adequate rest for cognitive health.

As we continue to explore the complexities of the brain, findings like these provide valuable insights into the mechanisms that help preserve our most meaningful experiences.

References:

Brodt S, Inostroza M, Niethard N, Born J. Sleep-A brain-state serving systems memory consolidation. Neuron. 2023 Apr 5;111(7):1050-1075. doi: 10.1016/j.neuron.2023.03.005. PMID: 37023710. https://pubmed.ncbi.nlm.nih.gov/37023710/
Yang W, Sun C, Huszár R, Hainmueller T, Kiselev K, Buzsáki G. Selection of experience for memory by hippocampal sharp wave ripples. Science. 2024 Mar 29;383(6690):1478-1483. doi: 10.1126/science.adk8261. Epub 2024 Mar 28. PMID: 38547293; PMCID: PMC11068097. https://pubmed.ncbi.nlm.nih.gov/38547293/
Buzsáki, G., & Watson, B. O. (2012). Brain rhythms and neural syntax: implications for efficient coding of cognitive content and neuropsychiatric disease. Dialogues in clinical neuroscience, 14(4), 345–367. https://doi.org/10.31887/DCNS.2012.14.4/gbuzsaki
Bisaz R, Travaglia A, Alberini CM. The neurobiological bases of memory formation: from physiological conditions to psychopathology. Psychopathology. 2014;47(6):347-56. doi: 10.1159/000363702. Epub 2014 Oct 3. PMID: 25301080; PMCID: PMC4246028. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4246028/