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

Abstract

BackgroundThe two ears are linked with a neural pathway such that stimulation of one ear has a modulating effect on the contralateral cochlea. This is mediated by cochlear afferent neurons connecting with olivo-cochlear efferents. The monitoring of this pathway is easily achieved by measuring contralateral suppression of otoacoustic emissions, and there is some clinical value in the ability to assess the integrity of this pathway. An important step in an evaluation of clinical utility is to assess any age-related changes. Accordingly, in the present study we measure the dynamics of contralateral DPOAE suppression in a population of normal hearing subjects of different ages.MethodsUsing a real-time DPOAE recording method we assessed contralateral DPOAE suppression in 95 ears from 51 subjects (age range 2–52 years). DPOAE (2f1-f2; f2 = 4.4 kHz; f2/f1 = 1.22) input–output functions were measured. In response to contralateral broadband noise, dynamic aspects of DPOAE suppression were measured, specifically suppression onset latency and time constants.ResultsAn age-related reduction in DPOAE amplitudes was observed. Both the detectability and the degree of contralateral DPOAE suppression were decreased in older age groups. We find an age-related increase in the latency of onset of DPOAE suppression to contralateral stimulation, but no significant change in suppression time-constants.ConclusionOlivo-cochlear function as revealed by contralateral suppression of DPOAEs shows some important age-related changes. In addition to reduced emissions (outer haircell suppression) we find an increased latency that may reflect deterioration in auditory brainstem function. Regarding clinical utility, it is possible that the changes observed may reflect an aspect of age-related hearing loss that has not been previously considered.

Olivocochlear Efferents in Animals and Humans: From Anatomy to Clinical Relevance

“…3 in Ref. ( 98 )]; (2) OAE suppression decreases with increasing age in listeners with normal audiometry ( 117 , 118 ); and (3) OAE suppression appears to be larger for OAE measured in the left than in the right ears ( 119 ), although other studies have reported greater suppression in the right ear ( 120 ). These factors (CAS bandwidth, age, and test ear) can differ across studies, which can make across-studies comparisons of CAS-activated MOC effects difficult.…”

“…Konomi et al ( 117 ) showed that the onset latency of DPOAE suppression by CAS increases with increasing age from about 60 ms for 2-year-old children to 150 ms for 50-year-old adults, without a change in the time constant of suppression. They argued that the increased latency might reflect deterioration in auditory brainstem function involved in the MOC reflex.…”

Cochlear Efferent Innervation Is Sparse in Humans and Decreases with Age

“…Because the MOC reflex is binaural, contralateral sound can activate MOC fibers to the ipsilateral ear and suppress responses such as otoacoustic emissions (Collet et al, 1990). Studies of "contra-sound suppression" suggest that MOC reflex strength declines with age (Kim et al, 2002;Jacobson et al, 2003;Konomi et al, 2014;Lisowska et al, 2014). Given the hypothesized role in the control of masking, this reflex decline may contribute to problems with hearing in noise in the aging ear.…”

Factors responsible for remote-frequency masking in children and adults

“…There are numerous datasets consistent with maturation of higher order processes, such as auditory stream segregation (e.g., Oh et al , 2001). There are also data on suppression of distortion-product otoacoustic emissions, an indicator of efferent function, indicating that the medial olivo-cochlear reflex is strongest in neonates and declines with each decade of life, from childhood into old age (Konomi et al , 2014). A stronger MOC reflex would be expected to improve performance when a signal is delayed relative to masker onset, but it is unclear how it would contribute to poorer thresholds in the gated condition, as observed in the present data.…”