Fruit fly 'tongue'

“We found that the fruit fly ‘tongue’ – taste sensors on its proboscis and front feet – can learn things using the same molecular pathways that the fly brain uses to learn things," Professor Neely said. "Central to this is the neurotransmitter dopamine."

“It turns out these are also the same chemical pathways that humans use to learn and remember all sorts of things,” Professor Neely said. “This really highlights how learning is a whole-body phenomenon; and was a complete surprise to us.”

Professor Wang, who led the study, said: “We were surprised to find that a protein-restricted diet that makes an animal live much longer also turns up the intensity of sucrose perception for that animal, and that is dependent on the same learning and longevity pathways.

“The response was also really specific. For example, when we fed flies food that had no sweetness, the animals’ sweet taste perception was enhanced, but only for glucose, not for fructose. We have no idea why they specifically focus just on one kind of sugar when they perceive them both as sweet.”

“We also found that eating high amounts of sugar suppressed sweet taste perception, making sugar seem less sweet,” Professor Neely said. “This finding, which occurs through a different mechanism, matched nicely with recent results from our colleague Monica Dus at the University of Michigan, who is the world expert in this area.”