Sleep, synaptic homeostasis and neuronal firing rates.

The synaptic homeostasis hypothesis (SHY) states that wake brings about a net overall increase in synaptic strength in many brain circuits that needs to be renormalized by sleep. I will review recent studies that were either specifically designed to test SHY or were interpreted accordingly, including several experiments that focused on changes in neuronal firing rates. I will emphasize that central to SHY is the idea that what is being regulated across the sleep/wake cycle is synaptic strength, not firing rate, and firing rate taken in isolation is not necessarily an adequate proxy for synaptic strength.