The forebrain song system in birds has access to auditory input, which is an essential element for both the sensorimotor phase of song learning and adult song maintenance.
Recent results demonstrate that auditory input into the song system is gated by behavioral state.
In awake animals that are not singing, neurons have highly regular, faster ongoing discharge and typically fail to respond to song playback. Urethane induced anesthesia shares some of the features of sleep, including auditory responses, bursting, and slower ongoing rates. In awake birds, injections of the muscarinic cholinergic antagonist scopolamine or the nicotinic antagonist DHBE generate sleep-like bursting in RA neurons. In all cases, significant auditory responses were later observed again, although not always at the same site, and commonly ongoing discharge rates recovered. In one experiment, this alteration of RA physiology was completely blocked with an injection of a nicotinic antagonist into HVc.