May 8 (UPI) -- Some people need to psyche themselves up to meet challenges head on. For flies, tough times call for a little shuteye.
New research suggests flies that are unable to fly sleep more as they learn to adapt to their disability.
The research -- published Friday in the journal Science Advances -- could offer insights into the evolutionary origins of sleep, as well as the role sleep plays in human health and development.
The sleep patterns of fruit flies are quite similar to those of humans. Young flies sleep more than older flies, with the need for sleep diminishing as a fly ages. Flies that are kept up all night catch up on sleep the next day. Caffeine keeps flies up, while antihistamines make them drowsy.
In humans, sleep is important for learning and neural development, and the latest research suggests flies rely on sleep for the same reasons.
After emerging from their pupal cases, newborn flies have a half-hour to spread their wings. If they don't, their development will be stunted.
For the new study, scientists placed baby flies in tiny containers, preventing the insects from opening their wings. Researchers also genetically modified fruit flies to prevent the expansion of their wings. In both instances, the flies were left flightless. Scientists also deformed the wings of older flies, rendering them flightless.
Having been robbed of their flight, all of the flies slept more than usual. During followup experiments, scientists confirmed that the same neural pathway responsible for communicating problems with a fly's wings sends signals for the fly to sleep more.
"When we identified the neurons that were activated when we cut or glued the wings of adult flies, they turned out to be the same neurons involved in the normal developmental process of wing expansion after emergence," Krishna Melnattur, researcher at the Washington University School of Medicine in St. Louis, said in a news release.
Infants, children and adolescents need more sleep than adults because their brains are growing and rapidly acquiring new information. The same is true for young flies. Sleep is essential as their wings develop and they learn to fly and navigate the world around them.
The challenge of being flightless appears to turn back the clock for flies and their sleep patterns.
"The whole circuit can get reactivated later in life when something happens that forces a fly to adapt to a new normal," said Paul Shaw, professor of neuroscience at the Washington University School of Medicine. "Suddenly, its brain needs to be as flexible as when it was young. It can no longer fly, but it still needs to get food, it needs to compete for mates, it needs to avoid dying. We think that sleep amplifies the brain plasticity the fly needs to survive."
Shaw and his research partners plan to conduct followup experiments to determine whether the added sleep actually pays dividends by allowing the disabled flies to develop new survival strategies. The ongoing research could also help scientists understand why some people sleep more than others, as well as pinpoint the origins of sleep disorders in humans.
"There's huge variation in sleep time among people," Shaw said. "Some people need five hours a night; some need nine. Sleep is an ancient process, and we've evolved mechanisms to change our sleep-wake balance to help us meet our needs."
"If these mechanisms get inappropriately activated, say by a traumatic event that triggers post-traumatic stress disorder, it can create a situation in which you're sleeping too much or too little and it's no longer matching up with your needs, and then you have a sleep disorder," Shaw added.