Effect of cortical activity enhancement on medial olivocochlear reflex

Abstract

The medial olivocochlear reflex (MOCR) is reported to protects the inner ear from acoustic overexposure. It has been shown that MOCR by fluctuations in cognitive function, e.g., attention and expectation. However, the mechanism by which the cortical cognitive processing modulates MOCR has not been clarified. To investigate this mechanism, we compared the variability of cortical activity and MOCR after a mental calculation task that demands widespread cortical network activities. Cortical activity was assessed by measuring slow vertex response (SVR). Although MOCR strength and SVR amplitude did not change significantly after the calculation task, two measures had reverse dependence on the difficulty of the calculation task; A moderately difficult calculation task increased SVR amplitude while reduced MOCR strength. The results implicate that MOCR variations can be attributed to cortical activity changes. In addition, by simultaneously measuring MOCR and EEG during the calculation task, the time course of the effect of the cortical modulatory effect on MOCR was also examined.