Can Scientists Reverse Memory Loss?

Decoding the Enigma of Amnesia After Repeated Head Impacts

Amid growing concerns about head injuries in athletes, a recent study from Georgetown University Medical Center and Trinity College Dublin explores ways to reverse memory loss linked to repeated head impacts.

Athletes, especially those in contact sports, face an elevated risk of head injuries. Annually, ~3.8 million concussions occur in the US due to sports-related injuries. The Center for Disease Control estimates that 5-10% of athletes may experience a concussion in any sports season.  Repeated head impacts, even minor sub-concussive ones, have been shown to cause chronic cognitive symptoms. As we delve into the consequences, addressing cognitive impacts becomes not just crucial but imperative.

Published in the Journal of Neuroscience in January 2024, the study investigates memory engrams and synaptic shifts triggered by high-frequency head impacts (HFHI). Previous research revealed these impacts cause chronic cognitive issues in mice through synaptic changes.

What is a synapse? Synapses are tiny gaps between nerve cells, crucial for transmitting signals throughout the body. Synaptic changes refer to alterations in these connections between neurons, acting like bridges between brain cells, facilitating effective communication. This study focuses on how repeated head impacts influence these synaptic connections, affecting how brain cells handle and recall memories.

In these experiments, scientists used special mice with genetic tweaks to understand how our brains store memories. These mice have "light switches" on their memory fingerprints, which helped researchers see how the brain keeps and uses memories.

This study played a crucial role in helping scientists grasp how repeated head injuries impact "memory fingerprints."

The findings revealed that head impacts make it challenging for the brain to access these memories, akin to the "light switches" getting stuck.

The study focused on mice that underwent a scary experience to comprehend how their brains retain and retrieve such memories. The mice were divided into two groups: one exposed to a fake treatment (sham), and the other to high-frequency head impacts (HFHI), mimicking repeated injuries.

When reminded of the frightening experience, mice treated with the fake procedure easily recalled it, whereas those with head impacts faced challenges in remembering. To delve into this, scientists examined their brain cells, concentrating on a crucial region known as the hippocampus.

The hippocampus acts as the brain's memory control center, playing a key role in organizing and processing memories. Think of it like a central hub for memory processes. When the mice treated with the fake procedure encountered reminders, the connections between their brain cells in the hippocampus adjusted, fine-tuning and enhancing their memory.

However, the mice with head impacts didn't experience the same adaptability in their hippocampus. The connections between their brain cells did not adapt as much, resulting in difficulties with memory recall.

To confirm that memory problems were indeed related to these changes, researchers carried out another experiment using optogenetics to stimulate memory cells in both groups of mice.

Optogenetics involves using light to control and manipulate specific cells in the brain, aiding our understanding and manipulation of how memories are stored and retrieved.

In simpler terms, repeated head impacts affect how brain cells handle and recall memories. These cells become less flexible, causing memory problems. Artificially activating memory cells, however, worked similarly in both groups, indicating the issue lies in how brain cells function rather than the memory itself.

This study, inspired by college football players' experiences, aims to bridge gaps between chronic traumatic encephalopathy (CTE) (a progressive brain condition believed to result from repeated head injuries), studies, and the impact of low-level head impacts in various sports, extending implications beyond athletics.

In summary, memory loss after a head injury is common. This study revealed that mice with repeated head injuries struggle to remember due to issues in their memory system. The problem is their inability to activate this system effectively, leading to forgotten memories. Improving these brain connections could be a way to treat memory problems caused by repeated head injuries.

This research offers hope to athletes and individuals grappling with memory problems following repeated head injuries. It hints at the possibility of addressing and potentially resolving memory issues resulting from head trauma, particularly in sports. While this is just the initial phase, it signals the potential for a future where sports participation doesn't have to compromise brain health.

Acknowledgments and Support:

Crucial support from Georgetown University's Mouse Behavior Core and NIH/NINDS grants underpins the study's progress. The authors declared no personal financial interests.

Written by Tiffany vanLieshout, PhD

Edited by Iana Malasevskaia, MD

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