How long has that smell been there? I realize that I’ve been smelling something for a couple of days.

Did I just notice it, or have I known about it for a while? Is it gasoline? Perception is messing with me, like in a dream when you've known something all along but can't remember first learning it. The smell didn't just arrive, this is just the first time I've named it. Except I can't name it, I can only not-name it. It's not rubber, it's not smoke, it's not plastic. It's The Smell.

Whatever chemical it is, something has spilled, or leaked, and gradually pervaded the house. Where is it coming from? It's not coming from anywhere. It's in the car too. How helpful: the not-gasoline / not-rubber is not-here and not-there. Now if I could only not-smell it.

Is it in my clothes? In my hair? Well yes. But not specifically. Maybe it's coming through the vents.

I'm a moron. Just ask.

"Hey what's that smell?"
"What smell?"
"The rubbery, metallic, gasoline smell that's been around"
"I don't smell anything".

I can't find it because it doesn't exist. I am imagining The Smell.

Days pass. I'm getting used to it, but really tired of it. I want it to leave me alone. I'm glad it's not real, If it was real gasoline-burning rubber I'd have a real migraine. It’s eerie how I can’t quite place it - it makes sense that it doesn’t actually exist because it’s not exactly like any of those things. It's not entirely constant, it has a rhythm of ebbs and flows.

Rarely, I notice it's gone. Then I hold my breath, cautious to breathe in. The Smell always returns.

---

A couple more days, and the case begins to crack. When the smell goes away, a trigger restarts it. If there's no Smell, then just the tiniest whiff of something plasticky or rubbery fires it up again. I still don't know how to make it stop, it just stops when it wants to, but I'm learning how it starts.

The trigger that starts The Smell is tiny - barely perceptible - like the outgassing of plastic, parts per million, say coming off a rubber spatula.

Another clue: when the trigger is gone, The Smell persists. But that's not how senses work! We don't keep seeing the color blue after the blue thing goes away. When I’m running a sound gig, and the sax player stops, I don't keep hearing the note-

-unless it’s feeding back.

Holy shit. It's feedback.

IT'S FEEDBACK!

I can't wait for it to go away again so I can probe this. I know feedback. Understanding feedback deeply, intuitively is daily life in live audio engineering. And this is exactly feedback. Feedback isn't just a sound continuing to ring, but that ringing is an amplification, looped through the system, that started as a small background noise, just a random disturbance, cranked up to 11.

The tiniest trigger is amplified, then the system continues to propagate the input, out of proportion to the stimulus, long after the input is gone.

My smell circuits are ringing, and resonating, at the feedback frequency of burnt rubber.

I'm buzzing with this discovery. Now what?

---

I liked and admired my high school Biology teacher, Mr. Davis. I clearly recall the chapter on signal transmission in the nervous system. A stimulus causes a nerve to fire, and the signal travels to the brain, crossing synapses along the way. The signal doesn't get a free pass at the synapse, it needs a special chemical present. The system provides that chemical, a neurotransmitter, but only briefly. The signal has a short window of time to pass, then the neurotransmitter is taken back up, preventing an excess of signals. Like in an audio circuit, the signal needs to be damped, else it keeps reverberating. If allowed to continue, it naturally recruits more neurons to fire along with it. The signal is amplified, just like in audio, and the runaway feedback here is what we call a seizure.

The Smell is neurological feedback. And neurological feedback... is a seizure. I'm having seizures?

I've reached the end of my ability to investigate.

---

I call a neurologist I know socially, a prominent Neurology department head at Hopkins. I've never asked a professional favor before, but this could be serious. I tell him my story and ask if the smells were like seizures.

"Yes, olfactory hallucinations can be epileptic. Have you taken any new medications recently?"

I freeze.

In this moment I regret calling on an expert for a favor, when any resident with an intake questionnaire would've sufficed.

"um, You mean, ... besides the Wellbutrin?"

I’d forgotten about meds. While I’d analyzed stimulus-response patterns, had a brilliant insight connecting audio circuits and my own neural pathways, recalled AP Biology from decades earlier, I'd still spaced about starting a psychopharm pill a week before the smell started.

"Yes, you can toss that bottle out right now," he says.

I had deduced from first principles (and crappy PA’s) that neurotransmitters were dallying in my synapses - which should surprise exactly no one since that is Wellbutrin's mechanism of action.

---

The Smell stopped after I tossed out the meds. Seizure-like activity is a known, but uncommon side effect, arising in 1 in 1000 to 1 in 250 patients. It wasn’t quite lottery odds, but also not common enough that my doc had specifically cautioned about it.

Every once in a while, The Smell returns, briefly, when I've stressed my system - with too much work or too little sleep. It’s still annoying, but a useful reminder to take better care of my neurons.

Epilogue:

The experience gave me a personal appreciation for people with chemical sensitivities. I've known people who can't be around strong smells, or certain chemicals. They’ll explain that they can smell plastic computer keyboards. I’d be skeptical that anyone could smell such things, if I hadn’t experienced it myself.

When those people have to speak up, say at a night class, or a book club, and ask the group to accommodate, it's socially risky. I saw firsthand that they are not exaggerating.