Broth on the Brain: Bangkok Noodle Soup for the Soul

A whiff exacts a slow exhale of comfort and calm, just to take in another waft of the cozy aroma. The bowl warms your hands, steaming out an invitation. A breath in carries this invitation up through the dark, skinny nasal canal passage, pulling it up against the nasal membrane and a bed of tiny hairs and microvilli. The molecules of brothy vapor that make up this whiff of flavor light up an assembly of scent receptor cells sprinkled in behind the membrane. The receptor cells’ gatekeepers – G proteins – wake to the signs of the soupy smell, sparking into action that then burns up ATP, letting the cell open its doors to calcium and sodium and finally project a pulse of unformed notions of soy sauce and cilantro upstream to the olfactory bulb.

All this and far more transpires before the brain even comprehends “delicious,” recognizing the thick but bright, savory smell of a bowl of Thai street noodles.

While our brains seem to intuit such connections naturally, it’s hard to communicate for someone else the strengthening assurance and relaxation that we connect to a dish of comfort food. There’s a feeling that the steam from a bowl of soup almost forces you to drop your shoulders and sigh. Mashed potatoes, grilled cheese, chicken soup, pot pie, Tex-Mex, grits, cinnamon rolls, much-loved-relative’s casserole. Butter. It’s personal, intimate and too simple to be explainable. In fact, neuroscientists are still stumped as to exactly how those scent molecules first trigger the receptor cells in our nose.

IMAG0161_1I’m sitting at an orange metal street-side table on one of the four thoroughfare spokes that leave Bangkok’s brightly-lit Victory Monument. I sit with and talk to a Singaporean man stopping on his nightly commute home. We don’t discuss the neuroscience of smell and memory in Thai, only our hunger.

My nest of noodles arrives curled up in a dark, sweet broth that floats strips of fresh green onion, cilantro, Chinese kale ribbons, ground peanuts and hard-boiled eggs, steeped long enough to dye their whites the deep caramel soy hue of the soup. I had also nodded at the maa kaa’s (แม่ค้า) offer of pillowy cubes of light fried tofu; pieces of braised pork belly top my tablemate’s bowl, Thai sweetbreads that look like ham hock. Easy appreciation sweeps in, a quiet thank-you to the unchanging rush of people and bikes and cooks and the sizzles of woks over fires and the vendors’ calls.

At our street stall of choice, the woman making Khai phalo (ไข่พะโล้), or a tweaked vegetarian version with noodles for the annoying foreigner, is a wizard over her cauldron. She wears tight long sleeves, floral and bird-patterned, to protect her arms from hot oil and broth. Noodles go into a strainer on a long metal rod that she dips into a bubbling vat with authority, single servings at a time, her hands then flying a knife over stalks of greens or handfuls of ginger and nuts. The noodles cook in seconds, she chops through long cuts of already-tender pork or blocks of fried tofu, everything piling up in a bowl with the noodles before eggs plop on top and broth fills the bowl.

Especially for those who harbor an appreciation for ramen, sitting down to a bowl is like getting a hug – a rarity in Thailand, given cultural differences around showing affection. It’s hard to make someone else understand where this “hugged” feeling comes from – this might be why I’m at a loss for words to convey the solace offered by this particularly lovin’ spoonful. I wish that every lonely soul out there trying to make a microwaved meal out of ramen knew this recipe.

Comfort foods and their scents are memories, relationships with past spreads on tables we pulled up to with family and friends who probably literally did indeed give us hugs. But the memories might be too faded for us to pick out exactly which scenes helped build these emotional associations – and the process certainly wasn’t intentional. Six year-old, baby-faced me didn’t tuck into a toasted, buttered, cinnamon raisin bagel while focusing consciously on new neural pathways and on “long-term potentiation.”

At some point in evolutionary history, however, the Darwinian powers that be saw to it that the human brain built the capability to deeply connect flavors or smells with both emotions and memories. To those dear friends with no sense of smell, Darwin must just hate you.

Electrical signals shoot upstream from the scent receptors, sparking neurons along familiar curves in the olfactory bulb. Each unique type of scent receptor behind our nasal membrane connects to a landing strip that blinks and brightens on the front half of the olfactory bulb, or the glomerulus. From there, our mitral cells are the workhorses that trek up even further, finally kicking the amygdala and hippocampus alive.

It’s at this stage that we forge associations between memory and smell, and the same holds true for our sense of taste. The amygdala and hippocampus link the olfactory bulb to a network of structures in our brain that handle feelings, conscious sensations and their long-term storage – both explicit and implicit. The scent-receiving cells before this point don’t live longer than six to ten weeks; the systems behind our sense of smell actually have a plasticity to them that other sensory systems lack.

Our brains’ evolutionary adaptations and plasticity over our lifetimes show that we value, unconsciously, links between smells and feelings. As humans age, we actually tend to strengthen our associations between specific foods and emotions; we prune away weaker memories while reinforcing older associations with comfort foods every time we eat them. All it takes is one scent particle – the human nose can recognize a smell at a concentration of just three particles for every billion particles of air around us. For comparison’s sake, if we could smell carbon dioxide, we would be overwhelmed by our atmosphere’s current concentration of 400 parts per million.

But while we’ve wound the pathways of our brain to form these bridges between scent and emotion, that doesn’t mean we know how to talk about them. It’s not just the limitations of my Thai language that keep me from telling my Singaporean tablemate why I hunted down just such a noodle stall tonight. It’s another hot night in tirelessly buzzing Bangkok, a world of opportunities and adventures, but I am alone on my hunt for sustenance. I don’t need a hug – and I wouldn’t ask the Singaporean guy for one – but I’ll take one for dinner.



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  1. An amazing, delicious soup you’ve served up here: lots of chunks of neuroscience, threads of comfort food memories, aroma of hugs, colorful bits of Thai, all floating in a nourishing broth of Bangkok local color/street life . . . Thank you so much for this!

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