Sleep Facilitates Memory by Blocking Dopamine Neuron-Mediated Forgetting

Early studies from psychology suggest that sleep facilitates memory retention by stopping ongoing retroactive interference caused by mental activity or external sensory stimuli. Neuroscience research with animal models, on the other hand, suggests that sleep facilitates retention by enhancing memory consolidation. Recently, in Drosophila, the ongoing activity of specific dopamine neurons was shown to regulate the forgetting of olfactory memories. Here, we show this ongoing dopaminergic activity is modulated with behavioral state, increasing robustly with locomotor activity and decreasing with rest. Increasing sleep-drive, with either the sleep-promoting agent Gaboxadol or by genetic stimulation of the neural circuit for sleep, decreases ongoing dopaminergic activity, while enhancing memory retention. Conversely, increasing arousal stimulates ongoing dopaminergic activity and accelerates dopaminergic-based forgetting. Therefore, forgetting is regulated by the behavioral state modulation of dopaminergic-based plasticity. Our findings integrate psychological and neuroscience research on sleep and forgetting. [Display omitted] •Dopaminergic activity underlying forgetting is regulated with behavior state•Sleep after learning improves memory by blocking dopaminergic signaling•Arousal accelerates forgetting by increasing dopaminergic signaling Sleep is generally thought to stabilize new memories, but early psychology studies suggest that it prevents new learning from interfering with old memories. This study shows that sleep suppresses the activity of dopamine neurons that promote active forgetting of olfactory memories in flies, providing integration between neuroscience and psychology research.