Age impact on the eferent system actitivies in cochlear mechanical properties in normal hearing individuals

Abstract

The medial olivocochlear tract has efferent control over the outer hair cells, regulating the slow contractions and damping the fast ones. Using ipsilateral, contralateral or bilateral otoacoustic emissions amplitude studies, it is possible to estimate the conditions of this tract, since the effect resulting from the reduction/suppression of these emissions indicate the tract's functioning. Aging implies an activity reduction in the central auditory system, because of the degeneration of the structures involved in hearing skills. Aim: our goal was to investigate the effects of age on the activities of this tract on the cochlea, through the analysis of the emissions' amplitude with contralateral acoustic stimulation. Materials and methods: Our series was made up of 75 individuals grouped according to age. The methodology was conventional, with a linear click and a white noise. Case study: the analysis considered the response from both ears and the comparison between the groups. Results: the results show a statistically significant difference between the emissions' response with and without contralateral acoustic stimulation in the individuals between 20 and 39 years of age. The emissions reduction/suppression effect reduced with age (fourth decade). Conclusion: aging impairs the tract effectiveness.

Age related changes to the dynamics of contralateral DPOAE suppression in human subjects

“…We use this example to indicate the general difficulty in comparing across studies that use differing OAE measurement methods and stimulation protocols. In our study we find a general reduction in DPOAE suppression amplitude with age that is in agreement with a number of previous reports [17-21,30,31]. The cause of the suppression amplitude reduction can only be speculated on.…”

“…Recent studies have reported a degradation of contralateral suppression of transient evoked OAE in human with advancing age [30,31]. Oliveira et al [31] evaluated such changes in subjects from 20 to over 60 years of age and showed that subjects over 40 yrs.…”

“…Oliveira et al [31] evaluated such changes in subjects from 20 to over 60 years of age and showed that subjects over 40 yrs. had a significant decrement of suppression effect compared with those in their second and third decade.…”

Evaluation of outer hair cell function and medial olivocochlear efferent system in patients with type II diabetes mellitus

“…The preference of stimulus is important in OAE test procedures because the appropriate stimulus can provide better results, especially in some specific measurements. Linear stimulation is more sensitive in detecting shifts in the TEOAEs recorded in the presence of competitive noise than in those recorded without competitive environmental noise (25,26). However, it has some technical limitations, and therefore some authors recommend using the nonlinear mode of stimulation in detecting CLS of TEOAEs in clinical settings (18)(19)(20).…”

Cochlear efferent innervation and function

“…Two papers indicate that OAE amplitudes and/or MOC effects on OAEs decrease in older subjects [45, 46]. One paper indicates that smoking lowers TEOAEs and MOC effects on TEOAEs [47], while another found MOC effects on TEOAEs went down with age in smokers, but not in non-smokers [48].…”