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.