Regulation of vocal precision by local noradrenergic modulation of a motor nucleus

Abstract

23Recent theories of norepinephrine (NE) function suggest that NE modulates the 24 transition between stereotyped, goal-directed behavior and more variable exploratory 25 behaviors that facilitate learning and adaptation. We provide evidence for context 26 dependent switching by NE that is analogous to this explore/exploit strategy in the vocal 27 system of the zebra finch (Taeniopygia guttata). Stimulation of the locus coeruleus, the 28 major source of norepinephrine in the brain, decreases song trial-to-trial variability 29 transforming the variable, exploratory "undirected" song into song that resembles the 30 more stereotyped, exploitative "directed" song males sing to females. This behavioral 31 switch is mediated by NE acting directly on a cortical motor nucleus that integrates 32 inputs from a premotor cortical nucleus and a basal ganglia circuit necessary for vocal 33 motor learning. These findings suggest that norepinephrine can act directly on the motor 34 system to influence the transition between exploratory and exploitative behavioral strategies.