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Motor- and auditory-related activity of identified HVC neurons in the
singing zebra finch
Alexay Kozhevnikov, Richard Hahnloser and Michale Fee
Bell Labs Lucent Technology
Nucleus HVC of the songbird plays a role in both song
generation and song learning. HVC projects to neurons
in the premotor nucleus RA, which generate complex
patterns of bursts during singing. HVC also projects
to Area X, a nucleus that is involved in song
learning. HVC neurons have robust auditory responses
to song playback in anesthetized birds. We have made
single-unit recordings of antidromically identified
RA-projecting (HVC[RA]) neurons, X-projecting (HVC[X])
neurons, and HVC interneurons in the singing zebra
finch. HVC interneurons spike at a high rate (~100Hz)
throughout the song. In contrast, projection neurons
display stereotyped high-frequency bursts of spikes
that are tightly locked to the vocal output. HVC[X]
neurons generate 0-5 discrete bursts per song motif,
while HVC[RA] neurons burst extremely sparsely - at
most once per motif. As a population, HVC[RA] neurons
appear to burst throughout the song, suggesting that
they form an explicit representation of time in the
song motif. We suggest that ensembles of active RA
neurons are directly driven, at each time in the
motif, by a subpopulation of HVC[RA] neurons that is
active only at that time.
It has been shown that distorted auditory feedback
during singing results in a decrystallization of the
zebra finch song. Our preliminary studies of the
auditory responses of HVC neurons during singing show
that their firing patterns are not affected by
distorted auditory feedback during directed song.