Humans who are isolated tend to get lonely. Loneliness has been a significant problem during the lockdowns resulting from the pandemic. The pandemic has also caused people around the world to eat more, leading to significant weight gain and less sleep. New research has shown that fruit flies, which are social creatures, suffer from some of the same problems as humans when they are socially isolated.
Researchers found in experiments that single fruit flies quarantined inside a test tube slept too little and ate too much after about a week of social isolation. Research showed how separation from the group leads to gene expression changes and changes in neural activity and behavior in flies. The study is one of the first animal models for studying biological reactions in the body to being lonely.
Researcher Michael W Young from Rockefeller University said flies have a specific response to social isolation. Young and his team found that loneliness had pathological consequences for the flies. Those consequences are related to changes in small groups of neurons, and the researchers say they have begun to understand what those neurons do. In the wild, fruit flies search for food and eat in groups and conduct other complex social interactions.
They typically sleep for 16 hours a day, including a full night’s rest and a nap in the middle of the day. The team found that two flies can be isolated together and had no significant changes. However, when a lone fly was isolated, they began to eat more and sleep less. Scientists found that a group of brain cells known as P2 neurons was involved in the changes in the sleep and feeding behavior of the fly.
Shutting down P2 neurons in isolated flies suppressed overeating and restored their sleep. The team believes P2 neurons are linked to the perception of the duration of social isolation and the intensiveness of loneliness. In their experiment, flies were engineered to sleep less to ensure lack of sleep didn’t cause overeating. The team also discovered that P2 neuron manipulation didn’t cause overeating or sleep loss in socialized flies. It was determined that only P2 neuron activity and social isolation caused the flies to lose sleep and overeat.