Plos Biol
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Animal circadian clocks are based on multiple oscillators whose interactions allow the daily control of complex behaviors. The Drosophila brain contains a circadian clock that controls rest-activity rhythms and relies upon different groups of PERIOD (PER)-expressing neurons. Two distinct oscillators have been functionally characterized under light-dark cycles. ⋯ Remarkably, light acts by inhibiting the LN-MO behavioral output and activating the LN-EO behavioral output. Finally, we show that PDF signaling is not required for robust activity rhythms in constant light as opposed to its requirement in constant darkness, further supporting the minor contribution of the morning cells to the behavior in the presence of light. We therefore propose that day-night cycles alternatively activate behavioral outputs of the Drosophila evening and morning lateral neurons.