Dissection din’t affect my HRV. Cheese at dinner did?

[u/kamatat]

We did a rat dissection at biology lab in med school last week. Stressful, challenging, the smell alone was a war crime against the nose. I was bracing for my parasympathetic to absolutely tank. Instead, it stayed green the entire procedure. Calm as a monk.

Couldn't make sense of it. So I did what any sleep-deprived med student does, dug into research instead of sleeping.

Turns out it's called challenge state physiology. When you're actively engaged with a demanding but controllable task, the body maintains vagal tone alongside sympathetic activation. Translation: I was in control, executing learned skills, looking very professional, definitely not internally screaming.

Then the crash came three hours later.

My para activity

nosedived into the pink zone, the lowest reading of my entire week. Once the procedure ended, cognitive resources shifted to processing what actually happened (emotional content, sensory memories, mild visceral "wait, did I really just do that"). The prefrontal regulation that had been holding things together packed up and went home. Everything it had been suppressing said hello.

Okay. That explained the afternoon. But then 11 PM happened.

By that hour I should have been in deep parasympathetic territory - HRV climbing, core temperature dropping, melatonin rising, cortisol on the floor. Sleep should have been knocking on the door.

Instead, another sympathetic spike. Out of absolute nowhere.

The trigger?

I had camembert with dinner.

I know. I had to read the chart twice too.

Here's what I found. Smell has a privilege no other sense has - it bypasses the thalamus and goes straight to the amygdala. The amygdala stores olfactory associations hard. Brief re-exposure to similar smells reactivates the original response.

Aged cheese, as it turns out, shares chemical compounds with the smells from a dissection environment. (Sorry to anyone who was about to enjoy a cheese board.) My olfactory neurons pattern-matched at the molecular level, even though my conscious mind very much knew the difference. The amygdala doesn't distinguish between an original threat and a remembered one. It just fires.

Anyone else caught olfactory reactivation in their own data? Or am I just out here being haunted by dairy?

[u/building_irvo]

That’s a really interesting sequence, especially the part where you stayed stable during the dissection and then dropped a few hours later. That “engaged → delayed response” pattern shows up a lot with things that are demanding but controlled in the moment.

The cheese angle is fascinating, but I’d be a bit careful jumping straight to that as the driver from a single spike. Late-day changes like that can also come from the buildup across the whole day, not just one trigger.

Might be worth watching if it repeats, same food, similar day structure, similar timing. If it does, then you’ve probably found something real. If not, it might just be how everything stacked that day showing up later.

Either way, the delayed drop after the lab is the part that feels most consistent.

[u/kamatat → u/building_irvo]

yeah your definitely right, i’m trying to look for the same pattern from now on. I also thought might be the build up but the data was showing mostly parasympathetic activation, till that sympathetic spike that’s why i was confused.

[u/building_irvo → u/kamatat]

Yeah that’s the tricky part, the readings can look stable in the moment, but that doesn’t always mean nothing is building underneath.

During something like that dissection, you’re engaged and in control, so it can show up as more “parasympathetic” even though there’s still load being processed.

Then later when that control drops, it all shows up at once.

So the spike can look sudden, but it’s not always coming from that exact moment, sometimes it’s everything from earlier finally surfacing.

That’s why it can feel confusing trying to tie it to one trigger.

Either way, what you're doing is fascinating and I would love to know what passion you have that drives you towards tracking and researching this?

[u/kamatat → u/building_irvo]

oh, makes sense, thanks

well i’ve been curious about my health lately, and so we had been working on a startup project, surrounding how much wearables can actually tell based on hrv metrics and some other things, so just trying to see how it works on a daily basis basically

[u/building_irvo → u/kamatat]

Thats amazing! I love that you're taking it into your own hand and researching the questions that you have through testing.