Scientists have identified neural pathways in an insect brain behind eating for pleasure, a discovery which could shed light on such impulsive eating pathways in the human brain.
"We know when insects are hungry, they eat more, become aggressive and are willing to do more work to get the food," said Ping Shen, a University of Georgia associate professor of cellular biology in the Franklin College of Arts and Sciences.
"Little is known about the other half-the reward-driven feeding behaviour-when the animal is not so hungry but they still get excited about food when they smell something great. The fact that a relatively lower animal, a fly larva, actually does this impulsive feeding based on a rewarding cue was a surprise," said Shen.
The research team led by Shen found that presenting fed fruit fly larvae with appetising odours caused impulsive feeding of sugar-rich foods.
The findings, published in Cell Press, suggest eating for pleasure is an ancient behaviour and that fly larvae can be used in studying neurobiology and the evolution of olfactory reward-driven impulses.
To test reward-driven behaviours in flies, Shen introduced appetising odours to groups of well-fed larvae. In every case, the fed larvae consumed about 30 percent more food when surrounded by the attractive odours.
But when the insects were offered a substandard meal, they refused to eat it.
"They have expectations," Shen said in a statement.
"If we reduce the concentration of sugar below a threshold, they do not respond anymore. Similar to what you see in humans, if you approach a beautiful piece of cake and you taste it and determine it is old and horrible, you are no longer interested," he said.
Shen's team also tried to further define this phenomenon-the connection between excitement and expectation. He found when the larvae were presented with a brief odour, the amount of time they were willing to act on the impulse was about 15 minutes.
"After 15 minutes, they revert back to normal. You get excited, but you can't stay excited forever, so there is a mechanism to shut it down," he said.
