High-frequency auditory feedback is not required for adult song maintenance in Bengalese finches

Male Bengalese finches do not normally change their vocal patterns in adult hood; song is stereotyped and stable over time. Adult song maintenance requ ires auditory feedback. If adults are deafened, song will degrade within 1 week. We tested whether feedback of all sound frequencies is required for s ong maintenance. The avian basilar papilla is tonotopically organized; hair cells in the basal region encode high frequencies, and low frequencies are encoded in progressively apical regions. We restricted the spectral range of feedback available to a bird by killing either auditory hair cells encod ing higher frequencies or those encoding both high and low frequencies and documented resultant chances in song. Birds were treated with either Amikac in alone to kill high-frequency hair cells or Amikacin and sound exposure t o target hair cells across the entire papilla. During treatment, song was r ecorded from all birds weekly. After treatment and song recording, evoked-p otential audiograms were evaluated on each bird, and papillas were evaluate d by scanning electron microscopy. Results showed that hair cell damage ove r 46-63% of the basal papilla and the corresponding high-frequency hearing loss had no effect on song structure. In birds with hair cell damage extend ing further into the apical region of the papilla and corresponding low-fre quency and high-frequency hearing loss, song degradation occurred within 1 week of beginning treatment and was comparable with degradation after surgi cal deafening. We conclude that either low-frequency spectral cues or tempo ral cues via feedback of the song amplitude envelope are sufficient for son g maintenance in adult Bengalese finches.