Developmental changes of susceptibility to auditory fatigue in young hamsters

Susceptibility to auditory fatigue was studied in young hamsters by using an evoked-potential criterion of sound-induced threshold shift. Animals aged 15, 28, 40, 54 and 85 days were anesthetized and stimulated with a continuous tone (3 kHz, 110 dB SPL) for 10 min. Threshold shifts 1 min post-exposure were highest in animals aged 40 days, and lowest in animals aged 15 or 85 days. Threshold shifts recovered within 100 min in 15- and 85-day-old animals, but required considerably longer to recover in the other age-groups. The data suggest that young hamsters pass through a critical period of susceptibility to auditory fatigue. Comparison of this critical period with various indices of the development of hearing in the hamster suggests that the developmental events underlying the critical period do not occur in the middle ear.