It turns out, a lot of French people find cheese gross. And that’s great news for science.
The French researchers behind a study published Monday in the journal Frontiers in Human Neuroscience wanted to figure out what happens in our brains when we recoil from certain foods. But they faced some obstacles.
Here’s the big one: When researchers study “aversion” — or why we avoid doing things — they can create their own reasons for subjects to avoid a behaviour. Small amounts of pain or monetary loss (with permission) can do the trick.
But it’s not so easy to study disgust with food. People dislike different flavours and textures, for different reasons. And forcing someone to find a food disgusting — say, by using chemicals to induce vomiting after trying some — is super unethical.
Fortunately, they found, many, many French people are grossed out by cheese — 11.5% of the 332 subjects they surveyed, a much larger group than for any other food.
So they took 15 cheese-haters and 15 people who liked cheese and stuck them in fMRI machines, which can measure blood flow through the brain. None of them knew they’d been selected based on their thoughts on coagulated milk.
(To clarify: A bit more went into selecting the participants than that. For example, they all had to be right-handed, have noses in good working order, and match each other in age.)
Now picture the scene from the perspective of one of these subjects. You enter a room with a giant fMRI machine and lie down. A researcher straps an oxygen mask to your face and slides you in. The machine thrums alive.
Standing outside, a researcher hooks a bottle of some mysterious liquid to the tube connected to your mask, and squeezes a pump. A smell floods your nostrils — cucumber. Wow, that’s strong.
Then the bottle switches, and another smell reaches you, and another. Fennel, mushroom, blue cheese, cheddar, goat cheese, pâté, Gruyère, peanut, Parmesan, pizza, tomme.
As the scents pumped in, you press one of five buttons, indicating how good or gross you find them.
(Again, there was a bit more involved, including a training session on how to breath safely and images flashing on a screen.)
An fMRI can’t see exactly which neurons light up in a subject’s brain. Instead, it uses a proxy to figure out what your brain is doing: blood flow. There are limits to this kind of research, because the findings are necessarily second-hand and fuzzy. But it’s useful for pointing toward some of the basic, underlying mechanisms in how your brain does its business.
The fMRI used in this study saw that folks who hated the smell of cheese saw unusual amounts of blood flow to three regions of the brain: the internal globus pallidus, external globus pallidus, and sunstantia nigra.
If those sound like nonsense words to you, you’re not alone. But it matters because theose are all regions of the brain believe to be involved in mechanisms of reward. That is, they usually light up when you really like something. But in this case they seem to be involved in the mechanisms of disgust.
This result gives scientists some clues about how disgust works in the brain, or at least some wayfinding hints to investigate the question further. (We can’t determine too much from one fMRI study on 30 French people, of course; previous studies have found other brain networks that are involved in the disgust response as well.)
But the next time you find yourself gagging at a chunk of Camembert on your plate, keep in mind that your aversion may well be a close neighbour to pleasure.
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