The Brain's Seahorse

On Sept 27, 2018, I read a headline: “Indelible in the Hippocampus, is the laughter.” The Hippocampus is the brain structure responsible for encoding and retrieving memories, so to me, this seemed like a punny joke. I followed the link and found an elegant description of how memory works in the brain (and remember, I used to work in a Hippocampus lab!). To my surprise, the clip didn’t come from a nerdy comedy, but from the testimony of Dr. Christine Blasey Ford1.

I don’t want to get political because it will detract from the important points I want to convey, but context: A judge nominated for the Supreme Court in the USA, Brett Kavanagh, has been accused of sexual assault in high school by Dr. Ford. Can I give Dr. Ford a Hero Cookie

While testifying to a panel of senators, live in front of an entire nation, about her experience with a sexual assault, Dr. Ford calmly, and with dignity, explains how traumatic memories are formed in the brain. #MyNewHero.

Senator: How are you so sure that it was he?

Ford: The same way I’m sure I’m talking to you right now. Basic memory functions. And also just the level of norepinephrine and epinephrine in the brain that sort of, as you know, encodes that neurotransmitter encodes memories into the hippocampus, so the trauma-related experience is locked there whereas other details kind of drift.

I wanted to take this month’s post to follow up with Dr. Ford’s lesson and help explain how memories and trauma work. With how powerful Dr. Ford’s story was, trauma and memory are no doubt going to be talking points in the future, and we owe it to ourselves to understand the science of her experience before we cast judgement on it.

Hippocampus.

The Greek word for seahorse, which was given to a seahorse-shaped brain area. I like to think of the Hippocampus as a label maker. The brain converts information from our senses into a type of neural code, called an engram (the scientific term for a memory trace, because “memory trace” apparently wasn’t scientific enough). The Hippocampus takes this memory trace, and slaps labels of what is happening, when, and where its happening2, and what you are feeling when it happened. It makes sense your brain would organize memories based on the event and its context, but why does it need to also encode your feelings? Well, some memories need to be trashed to make room for new ones, and the Hippocampus uses emotions to make this decision3. Essentially, the more boring it is, the more likely its going to be forgotten, and the more the memory resembles something related to paleo-era survival (location of food, water and other resources), the more likely our brain is going to keep that information4. This is why remembering the capital of Nova Scotia is more difficult than remembering which house has the dog that jumps at you. Only one of these things resembles important-to-survive information for a Neanderthal (sorry Halifaxians). For the most part, the Hippocampus can adapt to current-society survival information as well, like remembering social context rules (e.g. not walking in front of the Queen), and where the most budget-effective taco truck is (#gradschoolbudget). But sometimes it works too well, and memories are made so strong that they can’t be forgotten.

This is what happens when someone experiences a trauma. While the scary dog may resemble survival information, something like a sexual assault actually is a direct threat to your survival. Your body goes into extreme overdrive to try and combat the threat, and heightened levels of adrenaline tell your Hippocampus to never forget what’s happening. As a way to help make sure you don’t get back into that situation, your Hippocampus makes you re-experience your trauma whenever it's vaguely reminded of that situation. As you might guess, that isn’t very pleasant, and over time this starts to degenerate parts of the brain5, causing what seems like irrational behaviour. Clinically, we call this brain dysfunction Post-Traumatic Stress Disorder (PTSD). While PTSD is a complex disorder, its fundamental feature is an overactive Hippocampus memory system for extreme emotional experiences.5 Which returns us back to my original point.

This is why I think Dr. Ford demonstrated supreme courage. “Indelible in the Hippocampus, is the laugher”. The entire time she was on testimony being asked about her experience, Dr. Ford’s Hippocampus was making her relive aspects of that night, reminding her how threatened she felt. And yet, she persisted and calmly taught a room full of senators how memory works. Now knowing how her brain was making her feel, its easier to appreciate her courage and willpower. But what really makes Dr. Ford my hero, is her appeal to science. She reminded us all that a “perfectly detailed testimony” is not how our brain works, and hopefully, I helped give some extra insight into why the brain works that way.

Ty the Neuro Guy is a cognitive neuroscience graduate student at the University of Utah and the Research Director for Branch Out Neurological Foundation. Inspired by the creative knowledge translation, Ty helps promote scientific literacy through this blog. You can look forward to an article each month helping explain the science of NeuroCAM. If you have any questions or comments about this article or overall blog, feel free to email Ty McKinney at research@branchoutfoundation.com. 

 

 References

  1. Clip of Dr. Ford explaining memory https://www.youtube.com/watch?v=Y0gZxscRWpk
  2. Teyler, T. J., & Rudy, J. W. (2007). The hippocampal indexing theory and episodic memory: updating the index. Hippocampus17(12), 1158-1169.
  3. Phelps, E. A. (2004). Human emotion and memory: interactions of the amygdala and hippocampal complex. Current opinion in neurobiology14(2), 198-202.
  4. Allen, T. A., & Fortin, N. J. (2013). The evolution of episodic memory. Proceedings of the National Academy of Sciences110(Supplement 2), 10379-10386.
  5. Hull, A. M. (2002). Neuroimaging findings in post-traumatic stress disorder: systematic review. The British Journal of Psychiatry181(2), 102-110.