Differential behavioral engagement of inhibitory interneuron subtypes in the zebra finch brain

Inhibitory interneurons are highly heterogeneous circuit elements often characterized by cell biological properties, but how these factors relate to specific roles underlying complex behavior remains poorly understood. Using chronic silicon probe recordings, we demonstrate that distinct interneuron groups perform different inhibitory roles within HVC, a song production circuit in the zebra finch forebrain. To link these functional subtypes to molecular identity, we performed two-photon targeted electrophysiological recordings of HVC interneurons followed by post hoc immunohistochemistry of subtype-specific markers. We find that parvalbumin-expressing interneurons are highly modulated by sensory input and likely mediate auditory gating, whereas a more heterogeneous set of somatostatin-expressing interneurons can strongly regulate activity based on arousal. Using this strategy, we uncover important cell-type-specific network functions in the context of an ethologically relevant motor skill.