1. Kroodsma D. E., Miller E. H., Acoustic Communication in BirdsAcademic PressNew York1982.
2. Zann R., Anim. Behav. 40, 811 (1990).
3. Chew S. J., Mello C. V., Nottebohm F., Jarvis E. D., Vicario D. S., Proc. Natl. Acad. Sci. U.S.A. 92, 3406 (1995).
4. Vates G. E., Broome B. M., Mello C. V., Nottebohm F., J. Comp. Neurol. 366, 613 (1996).
5. Zebra finches (97 male and 96 female) obtained from our breeding colony were prepared for long-term recording as described (3). Auditory stimuli (11) were played from a speaker placed 0.5 m from the bird in a soundproof experimental chamber (3 12). During training the bird was freely moving; electrophysiological recording was carried out in awake restrained birds. Insulated tungsten microelectrodes were used to record physiological activity in the right or left caudal NCM at sites that exhibited habituation to novel songs (3). Recording sessions lasted ∼5 hours. All procedures conformed to an animal use protocol approved by the Rockefeller University Animal Care and Use Committee. The auditory stimulus and microelectrode data were digitized at 20 kHz. Single-unit action potential waveforms were digitally discriminated and displayed as rasters (Experimenters Workbench Datawave). Single-unit responses were quantified by averaging the firing rate during the stimulus period (plus the ensuing 100 ms) and then subtracting the firing rate during the control period (500 ms preceding stimulus onset). This mean firing rate per presentation was used to produce averages for example of 10 successive presentations (Fig. 1D) or of the first 50 presentations.