Sleep pressure modulates single-neuron synapse number in zebrafish.

Sleep is a nearly universal behaviour with unclear functions. The synaptic homeostasis hypothesis proposes that sleep is required to renormalize the increases in synaptic number and strength that occur during wakefulness. Some studies examining either large neuronal populations or small patches of dendrites have found evidence consistent with the synaptic homeostasis hypothesis, but whether sleep merely functions as a permissive state or actively promotes synaptic downregulation at the scale of whole neurons is unclear.