Bad experiences with food, such as a dodgy curry that makes us sick for days, cause a switch in our brain that means we never want to eat it again, a study shows.
British researchers have succeeded in repeating the effect of a negative experience on eating behavior by using sugar-loving snails as models in the laboratory.
They use ‘aversive training’, which involves slapping snails on the head when sugar appears, as a proxy for food poisoning in humans while being filmed.
Aversive training has made an appetite suppressant switch which means the snails refuse to feed sugar, not even hunger.
The experts believe that something similar is happening, leading to ‘persistent physiological change’ that is specific to a certain food for the rest of our lives.
That dodgy chicken tikka masala from four years ago can make us never want to eat the dish again – and researchers think they know why
“Effectively, a switch is turned in the brain, which means that the snail does not eat more sugar when it is presented with it, because sugar now suppresses rather than activates nutrition,” said Dr. Ildiko Kemenes told the University of Sussex.
Snails like sugar and usually start feeding on it as soon as it is presented to them, just like humans when they see sugary treats in the kitchen.
“Snails provide us with a similar but extraordinarily basic model of how human brains work,” said Professor George Kemenes, also of the University of Sussex.
“In our research, the negative experience the snail had with sugar can be compared to eating a bad take-away curry, which we then take away from that particular dish in the future.”
Despite their primitive appearance and reputation, there is a switch in snail brains that actually prevents them from eating too much.
Bad experiences with food, such as a dodgy curry that makes us sick for days, cause a switch in our brain that means we never want to eat it again, a study reveals
This appetite suppressant switch (ASS) is controlled by a neuron – a type of very excited 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 path,” said Dr. Ildiko Kemenes said.
“This is important because the network tends to be activated spontaneously, even when there is no food.”
“By suppressing the feed cycle, it ensures that the snail does not just eat everything and anything else.”
Researchers believe that something similar is going on in the human brain, and it is considered a natural tactic to protect us from obesity (although it is likely that some people’s appetite suppressants work better than others).
Usually, when food is present, this neuron is inhibited in snail brains so that nutrition can begin.
After the aggressive training of the hungry snails, researchers found that this neuron reversed its electrical response to sugar and became excited instead of inhibiting it.
The increased activity of the excited neuron actually turned on the ASS, which suppresses sleep appetites.
Most importantly, this effect was seen only for sugar – which is why the researchers compared it to the lasting psychological effects of people eating a specific meal that makes them sick.
Researchers placed snails in Petri dishes and exposed them to sugar and ‘strong tangible stimuli to the head’.
When researchers instead presented a piece of cucumber to the trained snails, they found that the animal still wanted to eat it.
It showed that the soft headaches during aversive exercises were only related to the specific type of food that was present at the time.
“We believe that in a human brain, a similar switch can occur where specific groups of neurons reverse their activity in accordance with the negative relationship between a particular food,” said Professor George Kemenes. .
The research also revealed that when the neuron was completely removed from trained snails, they ate sugar again.
“This suggests that the neuron is necessary for the expression of the learned behavior and to change the response to sugar,” said Dr. Ildiko Kemenes said.
“However, we can not rule out that the sugar-activated sensory pathway also undergoes changes, so we do not take the assumption that it is all in the brain.”
The study was published in Current Biology.