Problem:
I've been reading about Dorsal Raphe Nucleus, a serotonin- rich part of the brain. I noticed mentioning of "tonic activity" - regular pulsing that releases neurotransmitters. On top of this "tone" the nucleus can fire bursts of spikes(action potentials?) that further increase neurotransmitter concentrations for a short time.
Question: Is this kind of tonic firing common throughout the brain, or is it DRN specific? Please explain your answer.