Stratified Palliobulbar and Midbrain Circuits Control the Timing and Acoustics of Learned Vocalizations

In zebra finches, largely non-overlapping palliobulbar projections to medulla versus PAG separately control learned song acoustics and respiratory timing, with PAG also required for vocalization.

• Why it matters: Pallial supervision of brainstem circuits for learned vocalizations is unclear, despite progress in cortical and pallial coding of speech and birdsong.
• What they did: The study mapped pallial-to-brainstem organization in zebra finches, used genetic silencing of medulla and PAG pathways, and performed large-scale neuronal recordings including dual recordings from palliobulbar neurons and the PAG.
• The result: Medulla projections control learned acoustic content of syllables, PAG projections control respiratory timing, and PAG uniquely encodes song and innate calls; PAG-to-medulla silencing prevents learned song and innate calls.