Sleep- and wake-dependent changes in neuronal activity and reactivity demonstrated in fly neurons using in vivo calcium imaging.
Sleep in Drosophila shares many features with mammalian sleep, but it remains unknown whether spontaneous and evoked activity of individual neurons change with the sleep/wake cycle in flies as they do in mammals. Here we used calcium imaging to assess how the Kenyon cells in the fly mushroom bodies change their activity and reactivity to stimuli during sleep, wake, and after short or long sleep deprivation. As before, sleep was defined as a period of immobility of >5 min associated with a reduced behavioral response to a stimulus. We found that calcium levels in Kenyon cells decline when flies fall asleep and increase when they wake up. Moreover, calcium transients in response to two different stimuli are larger in awake flies than in sleeping flies. The activity of Kenyon cells is also affected by sleep/wake history: in awake flies, more cells are spontaneously active and responding to stimuli if the last several hours (5-8 h) before imaging were spent awake rather than asleep. By contrast, long wake (≥29 h) reduces both baseline and evoked neural activity and decreases the ability of neurons to respond consistently to the same repeated stimulus. The latter finding may underlie some of the negative effects of sleep deprivation on cognitive performance and is consistent with the occurrence of local sleep during wake as described in behaving rats. Thus, calcium imaging uncovers new similarities between fly and mammalian sleep: fly neurons are more active and reactive in wake than in sleep, and their activity tracks sleep/wake history.
['Bushey|Daniel|D|', 'Tononi|Giulio|G|', 'Cirelli|Chiara|C|']
D019342:Acetic Acid D000818:Animals D030801:Animals, Genetically Modified D002118:Calcium D002147:Calmodulin D004331:Drosophila melanogaster D005260:Female D049452:Green Fluorescent Proteins D007834:Lasers D036641:Microscopy, Fluorescence, Multiphoton D024521:Mushroom Bodies D009219:Myosin-Light-Chain Kinase D059906:Neuroimaging D009474:Neurons D010100:Oxygen D011993:Recombinant Fusion Proteins D012890:Sleep D012892:Sleep Deprivation D014851:Wakefulness
Kenyon cells mushroom bodies sleep deprivation GCaMP5