Brain pathways for learned and unlearned vocalizations differ in zebra finches

Area of Science:

• Neuroethology
• Avian vocalization
• Comparative neurology

Background:

• Male songbirds learn complex vocalizations, while females typically do not.
• Both male and female zebra finches produce a 'long call' when isolated, but males' calls have learned components absent in females.
• Learned features in male long calls, like frequency modulation and duration, resemble learned song elements.

Purpose of the Study:

• To investigate if the neural pathway for learned song production in male zebra finches is also involved in producing the learned components of the long call.
• To determine the role of telencephalic nuclei HVC, RA, and tracheosyringeal (ts) nerves in vocalization control.

Main Methods:

• Surgical manipulation of the neural pathway for vocalization in male zebra finches.
• Bilateral sectioning of tracheosyringeal (ts) nerves.
• Bilateral lesions of HVC and RA nuclei.
• Acoustic analysis of long calls and songs before and after manipulations.

Main Results:

• Ts nerve section in males altered fundamental frequency and frequency modulation of both long calls and songs, but not temporal structure.
• HVC or RA lesions in males affected fundamental frequency, frequency modulation, and temporal structure of both long calls and songs.
• Neither ts nerve section nor HVC/RA lesions affected the female long call, suggesting sex-specific neural control.
• Lesions to HVC and RA abolished learned features in male long calls, revealing a simpler, unlearned vocalization.

Conclusions:

• The HVC, RA, and ts nerve pathway is crucial for learned acoustic features in both male zebra finch song and long calls.
• Temporal structure of these vocalizations depends on HVC and RA, but not ts nerves.
• Learned vocalizations in songbirds are controlled by a telencephalic pathway interacting with pathways for unlearned vocalizations.