Behavioral state modulation of auditory activity in a vocal motor system.

Neurons of the song motor control nucleus robustus archistriatalis (RA) exhibited far weaker auditory responses in awake than in anesthetized zebra finches. Remarkably, sleep induced complex patterns of bursts in ongoing activity and uncovered vigorous auditory responses of RA neurons. Local injections of norepinephrine suggested that the changes in response strength occur through neuromodulatory control of the sensorimotor nucleus HVc, which projects to RA. Thus, motor access to auditory feedback, which zebra finches require for song learning and maintenance, may be regulated through neuromodulation. During sleep, the descending motor system may gain access to sensorimotor song memories represented as bursting patterns of activity.