Effects of a preceding sound on medial olivocochlear bundle reflex as a function of the preceding time interval

摘要

Our previous study reported that a preceding sound, regardless of whether it induced a medial olivocochlear bundle reflex (MOCR) by itself, expedites MOCR, and a 60-dB-SPL preceding-noise, which also induces an MOCR, that enhances, in addition to expediting, the MOCR. The current study compares the dependency of the enhancing and expediting effects on the preceding time interval. The MOCR is induced by sounds and exerts an inhibitory effect on the outer hair cells. The suppressive effect was assessed non-invasively in terms of the suppression of otoacoustic emissions (OAEs) induced by a contralateral acoustic stimulation, referred to as MOCR elicitor. A 60-dB-SPL noise was used as a preceding sound, and the inter-stimulus interval (ISI) between the preceding sound and the MOCR elicitor was varied from 0.5 to 2 s. The MOCR strength decreased as the ISI became larger and reached the same level as without a preceding sound within 2 s of ISI. In contrast, the onset delay of the MOCR did not depend on the ISI and was still significantly smaller than without a preceding sound even at 2 s of ISI. The difference in the dependency of the preceding time interval implicates that the preceding-sound-induced enhancing and expediting effects are underpinned by different mechanisms. Effects of a preceding sound on medial olivocohlear bundle reflex as a function of the preceding time interval