Bad experiences with food, like a dubious curry that makes us sick for days, trigger a switch in our brains that means we never want to eat it again, a study found.
UK researchers were able to replicate the effect of a negative experience on eating behavior, using sugar-loving snails as models in the laboratory.
They used ‘aversive training’, which involved patting snails on the head when sugar appeared, as a substitute for food poisoning in humans, during filming.
Aversive training triggered an appetite suppressant switch that meant that snails refused to feed on sugar, even when they were hungry.
Experts think that something similar is happening, leading to a ‘persistent physiological change’ that is specific to a particular food for the rest of our lives.
That dubious chicken tikka masala from four years ago may make us never want to eat the dish again – and researchers think they know why
“Effectively, a switch was triggered in the brain, which means that the snail no longer eats sugar when presented to it, because sugar now suppresses rather than activates food,” said the study’s author, Dr. Ildiko Kemenes , from the University of Sussex.
Snails like sugar and usually start eating it as soon as they are introduced, as do humans when they see sugary treats in the kitchen.
“Snails provide us with a similar, but exceptionally basic, model of how the human brain works,” said Professor George Kemenes, also from the University of Sussex.
“In our research, the negative experience that the snail had with sugar can be compared to eating a bad curry for travel, which will keep us away from that specific dish in the future.”
Despite their primitive appearance and reputation, there is a change in the snails’ brain that prevents them from overeating.
Bad experiences with food, like a dubious curry that makes us sick for days, triggers a switch in our brains that means we never want to eat it again, reveals a study
This appetite suppressant switch (ASS) is controlled by a neuron – a type of highly excitable cell that transmits information to parts of the body via electrical signals.
“There is a neuron in the snail’s brain that normally suppresses the feeding circuit,” said Dr. Ildiko Kemenes.
‘This is important, as the network tends to be activated spontaneously, even in the absence of any food.’
“By suppressing the feeding circuit, it ensures that the snail does not just eat anything and everything.”
The researchers think something similar is happening in the human brain, considered a natural tactic to protect us from obesity (although some appetite suppressant switches are likely to work better than others).
Normally, when food is present, this neuron in the snails’ brain is inhibited so that feeding can begin.
After the aversive training of the hungry snails, the researchers found that this neuron reversed its electrical response to sugar and became excited instead of inhibited by it.
This increased activity of the excited neuron essentially activated the ASS, suppressing the snails’ appetite.
Most importantly, this effect has only been seen in sugar – which is why researchers compared it to the lasting psychological effects of humans eating a specific meal that makes them sick.
The researchers placed snails in petri dishes and exposed them to sugar and “strong tactile stimuli for the head”
When the researchers presented the trained snails with a piece of cucumber, they found that the animal was still happy to eat it.
This showed that the gentle beating on the head during aversive training was associated only with the specific type of food that was present at the time.
“We believe that in a human brain, a similar change may be taking place where specific groups of neurons reverse their activity in line with the negative association of a specific food,” said Professor George Kemenes. .
The research also revealed that when the neuron was removed entirely from trained snails, they went back to eating sugar.
“This suggests that the neuron is necessary for the expression of learned behavior and for altering the response to sugar,” said Dr. Ildiko Kemenes.
“However, we cannot rule out that the sensory pathway activated by sugar also undergoes some changes, so we don’t assume that this is all that is happening in the brain.”
The study was published in Current Biology.