Effect of interrupting recovery on loss in cochlear microphonic sensitivity.

Abstract

A previous experiment [G. R. Price, J. Acoust. Soc. Am. 56, 183–189 (1974)] produced data that documented an early recovery process (ERP) measurable in the cochlear microphonic (CM) following intense stimulation. At that time, a hypothesis was advanced that if the ERP were interrupted by successive stimuli during intense intermittent stimulation, unusually large losses would result. The present experiment tested this hypothesis by comparing loss in CM sensitivity in the ears of anesthetized cats following one of three exposure conditions: (1) intermittent stimulation timed to interrupt the ERP (1 min on, variable off time), (2) the same amount of stimulation with a maximum of recovery time (1 min on, 9 min off), (3) and continuous stimulation. All ears received 30 min of stimulation with a 5.0-kHz tone at 30 dB above that intensity necessary to produce a maximum in CM output. Interrupting the ERP when 5 dB from completion resulted in 1.2 dB/min of loss, while allowing it to run to completion produced losses of only 0.6 dB/min. Continuous stimulation resulted in 0.9 dB/min of loss. The data supported the hypothesis and demonstrated the importance of the ERP. The implications of these findings for the problem of hearing loss to intermittent stimulation are discussed. Subject Classification: [43]65.66, [43]65.40.