Like human teenagers, busy fruit flies with an active social life need extra sleep, scientists have found.
The insects were monitored by scientists as they flew around a laboratory ‘fly mall’.
Being set free into the enriched environment caused the flies to grow many new neural branches and synapses.
This in turn caused the flies to need more sleep, as the wiring in their brains returns to a simpler state to conserve energy.
The study provides evidence for the theory that ‘synaptic homeostasis’ is one of the key reasons all animals have to sleep.
It involves cutting the number of nerve connections and ‘synapses’ linking brain cells that have been made during the waking hours.
‘Sleep prunes back the new synapses,’ said Dr Chiara Cirelli, a sleep researchers from the University of Wisconsin-Madison.
‘You have to create space for synapses to grow again or you can’t learn again the next day.
‘Even more importantly, the pruning saves energy, and for the brain, energy is everything. Learning without sleep is unsustainable from an energy point of view.’
The research is published in the journal Science.
In one experiment, scientists released groups of young fruit flies into a large lit chamber that allowed them to fly around together for 12 hours.
Previously, the flies had spent the first days of their lives alone in single tubes too small to allow flying.
Being released into the ‘fly mall’ caused the flies to grow many new neural branches and synapses.
After a busy day, the insects were placed back into the single tubes and slept much longer than they had before. Their synapses returned to a more relaxed state after sleep.
Flies that visited the mall but were deprived of sleep continued to grow larger, denser synapses.
The scientists also looked at the role of the gene Fmr1 which when lacking in humans leads to Fragile X syndrome, a cause of autism, mental disabilities and an inability to sleep.
They discovered that when there is too much Fmr1 protein, synapses are not boosted during wakefulness and the need for sleep declines.