It has been suggested that synaptic weakening occurs during sleep to counterbalance daytime synaptic strengthening. The authors found that sleep was associated with a reduction in the level of postsynaptic AMPA receptors compared with awake periods, indicating homeostatic scaling down. The mechanism involves expression of the transcription factor HOMER1A; during the day, HOMER1A expression increases at non-synaptic locations, but at sleep onset the protein is recruited to the postsynaptic density, where it drives AMPA receptor removal and synaptic weakening.