Fig. 1.

Birds that sang degraded song after treatment had greater hair cell loss than birds that sang stable (like pretreatment) song after treatment. Birds that were allowed to recover from treatment for 8 or 14 weeks regained normal hearing in the low frequencies and near normal hearing in the higher frequencies. A, Percent of total papilla area missing original hair cells is plotted for birds with stable song after treatment and birds with degraded song after treatment. B, Threshold curves showing hearing thresholds for birds with profound hearing loss and degraded song immediately after treatment [▵; data from Woolley and Rubel (1999)], thresholds for birds that were also treated but maintained stable song (○), thresholds for birds that were treated, showed song degradation, and recovered for 8 or 14 weeks (▴), and normal birds (▪). Error bars represent ± SEM.