The neuroscience of taste
2:07PM, Aug 14, 2012
I’m not sure about your occupation, but neuroscience parties are pretty boring. The only thing I got out of them was a survival course in social skills. I learnt never to ask what research a colleague was doing. This question inevitably led to my brain sending orders to my spleen to come up and choke it to escape the boredom.
Instead I began to ask quirky questions about people’s lives in any domain other than the professional. I learnt fascinating things that way. One eminent professor spent his free time as a member of a wolf pack (comprised of like-minded humans) that met monthly in a den, and he was considering getting fur implants all over his body. Anyway, I digress. A more topical question I used to ask was, “What is the best meal you’ve ever eaten?”
Most people have an answer to this question. The answers are often interesting enough in themselves, but for years the thing that has fascinated me is why? What made it the best meal out of the tens of thousands they’d had?
Neuroscience has some perplexing things to say about this. When food hits the tongue only five elemental tastes can be registered: sour, sweet, bitter, salty and umami (olfaction adds a lot of complexity but is outside the scope of this piece). The question is, how do these five taste receptors transmit all the phenomenal richness that we experience as a meal? What makes a lobster bisque so different from a gazpacho, or even from a seafood chowder?
The neuromechanics are intricate but quite straightforward: a different number of the tongue’s thousands of tastebuds are stimulated by any particular food. This information is coded by first-order neurons (these carry signals from your tongue to your brain) before the signals have even entered the brain proper. These neurons have graded potentials, meaning they’re transmitting not just “yes/no” information but “how much” or “how strong”. At this point, thanks to the factorial expansion of the information as it passes through neurons downstream, we can already encode a mind-boggling amount of information.
Interestingly, this now complex information is sent first to the emotional part of the brain, the limbic system. This probably explains why both smells and tastes can potently recall vivid memories and emotions. The limbic system adds “colour” and then sends the percept to higher cortical areas that are important for conscious awareness.
This still leaves a lot to be explained. For example, say we can now encode and differentiate every taste: it doesn’t explain how flavour 7,643,254 gives me the experience of biting into a crisp, fresh, juicy, slightly tart pink lady apple. I think there are more profound, more human factors at play in explaining our enjoyment of food. Ones that neuroscience may never be able to explain.
The best meal I’ve ever eaten was a bag of freeze-dried lamb and peas that weighed 115gm before boiling water was poured into its packet. I was sitting in a snow cave I’d dug into a mountain in Aoraki/Mount Cook National Park in the middle of a ferocious blizzard. That bag of food was my link through death to life.
However, that wasn’t something I was thinking about at the time. The food simply tasted delicious. Every tiny, precisely cubic piece of steaming, rehydrated lamb seemed a universe of flavour and intoxication.
If I was to go into my pantry now and boil up a packet it would taste like dirt (I’ve tried this experiment). What can explain this difference? Epicurus has a couple of things to say about this. Despite what is often now attributed to his name, Epicurus did not advocate gluttony, or overindulgence of any of the senses. Rather, he said that pleasure, or good, comes from the eradication of imbalance. Food is good because it eradicates hunger. Eating too much is bad because it leads to discomfort and imbalance. In that snow cave I was hungry, exhausted and cold, and the desiccated food brought me back to balance, brought me rushing into pleasure. All sorts of rewarding chemicals were being released in my brain, which somehow get enmeshed with the experience of taste.
The second thing that Epicurus said about pleasure was that it was absence of pain. To Epicurus, a quiet balanced meal with good friends, free from trouble, was the ultimate pleasure. Not coincidentally, I was in that snow cave with my partner.
Think about your favourite meal of all time. I’m sure the food was fantastic in a technical sense, but I would hazard a guess that it also involved good friends and an occasion that was special in some way. We intuitively understand that the food enhances the occasion, but the occasion also makes the food.
ILLUSTRATION ANTONIA PESENTI
This article was published in the September 2012 issue of Australian Gourmet Traveller.