AUDITORY-PERCEPTION FOLLOWING HAIR CELL REGENERATION IN EUROPEAN STARLING (STURNUS-VULGARIS) - FREQUENCY AND TEMPORAL RESOLUTION

Behavioral detection thresholds, auditory filter widths, and temporal modulation transfer functions were obtained from four starlings before , during, and after 11 days of subcutaneous injections of kanamycin, a n aminoglycoside antibiotic. Birds were operantly conditioned to respo nd to pure tones and amplitude modulated noises ranging in frequency f rom 0.25 to 7 kHz using adaptive staircase procedures and were tested daily for 92 days after the first injection of aminoglycoside. All bir ds had threshold shifts of at least -60 dB at frequencies above 4 kHz. Lower frequencies were affected in some birds, although none of the b irds had hearing loss below 3 kHz. All four birds had wider auditory f ilters at 5 kHz immediately after the aminoglycoside series, Any chang es in frequency resolution at frequencies below 5 kHz were slight, tra nsitory, and rarely observed. Two of the four birds had permanently wi der auditory filters at 5 kHz. Temporal modulation transfer functions were briefly affected in two birds during the time of greatest thresho ld shift. Recovery of detection thresholds began soon after the inject ions ceased and continued for approximately 60 days. Recovery in frequ ency resolution lagged behind auditory threshold by about 10 days. Nor mal temporal resolution was observed in the context of impaired intens ity and frequency resolution. Changes in auditory threshold and freque ncy resolution were closely associated for all birds at 5 kHz, but wer e correlated with statistical significance in only two birds. Scanning electron microscopy was performed on all four birds after 90 days of recovery and confirmed that the extent of initial damage was consisten t with the pattern of observed hearing loss. (C) 1998 Acoustical Socie ty of America.