Rest in Drosophila is a sleep-like state

Periods of fly inactivity were tested against the behavioural criteria for sleep rather than assumed to be sleep: arousal threshold was measured with mechanical stimuli, the state was checked for rapid reversibility, flies were deprived of rest and the subsequent rebound measured, and the state’s response to caffeine and antihistamines was recorded.

Studied in

Drosophila melanogaster

Sample size

multiple cohorts of flies across behavioural and pharmacological tests

Inactive flies showed a raised arousal threshold, adopted a characteristic posture, and after deprivation rested substantially more than usual — a homeostatic rebound. Stimulants reduced the state and antihistamines increased it, as they do in mammals.

• Deprivation by mechanical disturbance is stressful, and stress alone changes behaviour.
• Behavioural criteria only — a fly brain is not recorded the way a mammal’s is.
• One species under laboratory light cycles that do not resemble a field environment.

• Keeping a fly awake to find out whether it was asleep

  Flies stop moving for hours at a time. Is that sleep, or just an insect standing still?

• Animal sleep

  An animal that has stopped moving is not thereby asleep

• Animal sleep

  Keeping an insect awake makes it worse at its job the next day