Individual Differences in Auditory Brainstem Response Wave Characteristics

Abstract

Little is known about how outer hair cell loss interacts with noise-induced and age-related auditory nerve degradation (i.e., cochlear synaptopathy) to affect auditory brainstem response (ABR) wave characteristics. Given that listeners with impaired audiograms likely suffer from mixtures of these hearing deficits and that ABR amplitudes have successfully been used to isolate synaptopathy in listeners with normal audiograms, an improved understanding of how different hearing pathologies affect the ABR source generators will improve their sensitivity in hearing diagnostics. We employed a functional model for human ABRs in which different combinations of hearing deficits were simulated and show that high-frequency cochlear gain loss steepens the slope of the ABR Wave-V latency versus intensity and amplitude versus intensity curves. We propose that grouping listeners according to a ratio of these slope metrics (i.e., the ABR growth ratio) might offer a way to factor out the outer hair cell loss deficit and maximally relate individual differences for constant ratios to other peripheral hearing deficits such as cochlear synaptopathy. We compared the model predictions to recorded click-ABRs from 30 participants with normal or high-frequency sloping audiograms and confirm the predicted relationship between the ABR latency growth curve and audiogram slope. Experimental ABR amplitude growth showed large individual differences and was compared with the Wave-I amplitude, Wave-V/I ratio, or the interwaveI–W latency in the same listeners. The model simulations along with the ABR recordings suggest that a hearing loss profile depicting the ABR growth ratio versus the Wave-I amplitude or Wave-V/I ratio might be able to differentiate outer hair cell deficits from cochlear synaptopathy in listeners with mixed pathologies.

Age-related changes in envelope-following responses at equalized peripheral or central activation

“…Decline in OHC function as measured by DPOAE will also play a role in auditory declines with aging [Lai and Bartlett, 2015, Sergeyenko et al, 2013] but does not appear to affect estimates of central gain [Verhulst et al, 2016] since all AN fibers would be affected. Although there are differences between aging and noise exposure, both can produce mixed OHC and IHC-AN damage, and the relative degree of that damage may affect individual changes in ABR and EFR measures [Bharadwaj et al, 2014, Verhulst et al, 2016, Zhong et al, 2014] and auditory nerve measures [Kale and Heinz, 2012]. As shown previously [Parthasarathy et al, 2010] and in Figs.…”

Applicability of subcortical EEG metrics of synaptopathy to older listeners with impaired audiograms

“…Especially in the oHI group, 16 the ABR Wave I at lower SPLs were often too weak to be reliably extracted from the recordings. 17 It can therefore only be suspected that the ABR Wave-I amplitude for the oHI group was 18 strongly reduced by high-frequency OHC loss as computational modelling work has predicted 19 (Verhulst et al, 2016). On the other hand, the ABR Wave V is very robust in humans and is 20 believed to be generated in the lateral lemniscus and inferior colliculus (Melcher et al, 1996; 21 Møller and Jannetta, 1985).…”

“…Aging listeners with 7 impaired audiograms are thus likely to suffer from both OHC deficits and synaptopathy, 8 rendering the interpretation of electrophysiological metrics complicated as the metrics can be 9 affected by both deficits. The quantification and isolation of cochlear synaptopathy from other 10 coexisting contributors of hearing loss is therefore still a major unsolved problem in hearing 11 diagnostics (Hickox et al, 2017;Kobel et al, 2017;Plack et al, 2016;Verhulst et al, 2016). 12 As a first step to disentangle peripheral hearing deficits from a single electrophysiological 13 metric, we investigated whether existing ABR/EFR metrics for synaptopathy diagnosis in a young 14 NH (yNH) group (25±4.1 years) follow the same trends for an older hearing impaired (oHI) group 15 (65±7.9 years) with high-frequency sloping audiograms.…”

“…The DPOAE thresholds roughly 7 correlated with the pure tone detection threshold measured at the same frequency using a two-8 alternative forced-choice adaptive tracking procedure and insert earphones (ER-2 with ER10-B, 9 Etymotic Research, Elk Grove Village, IL, USA). Further details on the DPOAE threshold 10 procedure can be found in Verhulst et al (2016). Participants were informed about the 11 experimental procedures according to the ethical guidelines at the University of Oldenburg.…”

Biomarkers for Hearing Dysfunction: Facts and Outlook

“…In humans, supra-threshold ABR wave fine structure analysis is becoming a useful tool for detection of hidden hearing loss [54,85,86] . In addition, ABR peak latencies ( Fig.…”