The Chemosensitive Organ

Diving off the deep end, I had an olfactory moment the other night that was a bit amazing, a bit scary. Amazing because I may have unlocked a new dimension of olfactory experience for myself, scary because I might be detecting the first real glimpse of neurological dysfunction that awaits my aged, exasperated mind.

Smells are like that. There are moments when I catch a whiff that is so faint, and so impossible to detect (like the mold that grows on the metal of your umbrella), that I often have to consider the myriad olfactory hallucinations that beset our chemosensitive organ, of which there are many.

It was a hot summer night. The crazy smell experiences always start out like that. Odors love heat, because evaporation is what makes them mobile; heat is the odor motor, if you will.

On this hot, sweaty night, I was eating dinner, hot and sweaty, resting my arms on my high-topped table, when I became fussed over the cleanliness of the surface of my table. My resting forearms sheathed in a thin film of slightly sticky, waxy sebum, and my tabletop layered in a similar compound from previous nights of the same scenario. "I need to clean this damn table. It's gross."

I try to keep my arms off the table. But it's a high top, and it's more comfortable for me to hunch over my bowl of gruel, resting on the underside of my forearms. I keep losing the battle, touching my sticky gross arms to the sticky gross table, then remembering not to, sitting straight up, only to capitulate again moments later.

All the while, I'm sampling my dinner, and very thoughtfully. I tried a new recipe last night, and today are the leftovers. The leftovers always taste different, and for some things, even better. The lemon juice in the marinade, the Maillard on the cast iron; What happened there? I used soy sauce and lime last time. What's the difference now? The acid, more sour; The surface texture, less caramelized. I am thinking, but with my mouth, my nose, lost in gustatory, olfactory thought. Shit! Dirty sticky table! And then it happened. Mid-bite, mid-thought, I could smell the table with my forearm.

That's right, mid-bite, the sensations of my dinner coalesced with the sensations of my forearms, and all of the sudden I could taste the table. Not even sure how to describe the taste, it didn't last long enough. My friend who knows a bit about these things says it's synaesthesia, hallucination. I'm not sure. I don't recall ever reading or hearing about this, but the science of smell is more mystery than science.

Our skin is covered in sensory receptors. Our olfactory cortex is entwined with our immune system. There is a hell of a lot going on here. I'm convinced that the reason I can smell mold in ways nobody else seems to be able to is because I trained (inadvertently through paranoia) my immune system in concert with my olfactory system to recognize it, and after a severe and prolonged exposure event in a basement apartment. The two -- immune and olfactory system -- now work together to alert me to its presence in the most impossibly minute airborne concentrations.

And now, I am suspicious that it goes way deeper. Then again, as I said at the outset, I may be slowly and steadily rolling into cognitive decline, my neural tendrils twisting, knotting, brittle and breaking. At least I'm taking notes.

Notes:
Pattern recognition receptor (PRR)   
A receptor present on the surface of keratinocytes and other cells of the innate immune system that recognizes microbe-specific molecules that are recognized by a given PRR are called pathogen-associated molecular patterns (PAMPs) and include fungal glucans...They are also called primitive pattern recognition receptors because they evolved before other parts of the immune system, particularly before adaptive immunity...The innate immune system is an older evolutionary defense strategy, relatively speaking, and it is the dominant immune system response found in plants, fungi, insects, and primitive multicellular organisms. 

The Olfactocracy

I’m not stinking drunk, You’re stinking drunk

No, you don't have to eat your broccoli.

In an experiment that sounds like something we should have done like 70 years ago, we discover that all noses are not created equal. We all smell things differently, perceiving particular odor-features with varying levels of intensity.

I take it back; we didn't have the ability to do this kind of genetics testing 70 years ago. This new experiment showed that of the ~400 genes that control our ~400 different olfactory receptors, the variability is on high. In other words, let's say broccoli has a bunch of different chemicals that make it smell like "broccoli," and that there's a bunch of different receptor-genes that code for those chemicals -- you and I have slightly different versions of those receptors, which make one of us more sensitive to the bad parts of the smell, and maybe even the other of us more sensitive to the good parts.

What you get is one person who doesn't mind eating broccoli, and one of us who gets less ice cream after dinner everytime broccoli's on the menu.

What you also get is an entire sense which lacks in consensus. At the genetic level, what smells good to you won't necessarily smell good to me. So how do we agree?

As groundbreaking a breakthrough as this is, it doesn't even begin to scratch the surface as to how different each of our olfactory experiences are. Each one of us really does live an olfactory world all to ourselves.

We know then that genetics separates us, but it goes even further. Genetics is the hardwiring, but what about the softwiring? If you, for example, were force-fed broccoli while at the same time you're also forced to watch, with your eyes pried open, footage of people trying to peel the foil off a Nutella jar but it rips halfway through, then you might become traumatized by the smell of hot broccoli, and hence highly sensitive, and highly averse to it.

And the reverse can also happen. Don't like Flowerbomb? Wait until you have a few too many romantic encounters with a woman who wears it, and you'll change, you'll see.  That's softwiring. Humans are special because of our neural plasticity, so you can bet we're susceptible to these kinds of changes.

The final note here needs to be on the way we talk about smells. If we all smell a bit different, then how can we really communicate our experiences to each other with any fidelity? 

Image source

Notes:

Genetic variation across the human olfactory receptor repertoire alters odor perception

C. Trimmer, A. Keller, N. R. Murphy, L. L. Snyder, J. R. Willer, M. H. Nagai, N. Katsanis, L. B. Vosshall, H. Matsunami, and J. D. Mainland

PNAS May 7, 2019 116 (19) 9475-9480; first published April 30, 2019

https://doi.org/10.1073/pnas.1804106115

You Will Never Smell My World the Way I Do

Heather Murphy for the New York Times, May 2019

Crowd Breath

Environmental surveillance is going to change the way we do things around here.

I'll never forget the day I heard Michio Kaku tell me that my toilet bowl would one day know more about me than my doctor. It was one of the most obvious examples, yet something so benign-sounding that it's never offered as a prediction of the future.

Talking toilet bowls do not make the most clickworthy headlines. Or do they? Maybe I'm not the most prescient clickbait writer. Maybe Google already has a patent on the Smart Bowl. (They do, just checked.)

More examples of environmental surveillance are already among us, like any home security system. These systems are listening to your whole house. They might even be listening to your footsteps with their gait-recognition algorithm-ears.

But today we're here to talk about the ability to measure the collective emotional signature of large groups of people. This particular study is innocuous – it looks at the release of isoprene via our breath, and as a result of the physical agitation that we experience when watching an intense film.

The researchers who came up with this stuck a mass spectrometer (basically a human offgassing detector) inside the HVAC of the movie theater, and roll the film. As the crowd reacts, they involuntarily release chemical signals that reveal their emotional state.

This technique is used to gauge the stress-inducing effects of a film, to thereby classify it for various age groups. We don't want kids watching films that are too intense. But you can easily imagine this being used for a multitude of purposes. For example, imagine a school where every classroom is outfitted with this equipment, monitoring the collective stress levels in every room, ready to dispatch a security guard without the need for a teacher to call the principal's office.

Image source

Notes:

We might be able to rate future films with a sniff test

Oct 2018, Ars Technica

Proof of concept study - Testing human volatile organic compounds as tools for age classification of films

C. Stönner et al, PLoS ONE, 2018

The Future of Humanity, new book (2018) by Michio Kaku

Also check out his radio show on WBAI 99.5FM

What's next for smart homes - An Internet of Ears?

Nov 2018, phys.org

Drone detects heartbeat and breathing rates

Sep 2017, BBC

Post Script:

All this talk of home security does remind me of the ancient Japanese technique of the Nightingale floorboards, which were a lo-fi security device. The placement of tiny metal strips under the floor rub against each other when you walk on them, chirping your arrival.

https://en.wikipedia.org/wiki/Nightingale_floor