Life experience and the asymmetry of the human auditory system: clinical and auditory science laboratory implications

Dale Hewitt

doi:10.12688/f1000research.14982.1

Abstract

It is now almost 60 years since Doreen Kimura first described the asymmetries of the human auditory system (HAS). It is 30 years since Kenneth Hugdahl, and almost 15 years since David Poeppel, did the same. Our knowledge of these asymmetries is now considerable and detailed. Here we review some of the literature concerning what is known about the asymmetry of the HAS, and use it to construct a simple model of how the central and peripheral components work together. The model details some of the asymmetry, the life-experience-dependant maturation of this asymmetry throughout the first two decades, possible reasons for the population variance in speech-in-noise perception, the central role of the corpus callosum, the involvement of the efferent auditory pathways, and the corticofugal control of the peripheral auditory system. Although our knowledge of HAS asymmetry remains incomplete, this should not prevent the introduction of required changes to the current practices of audiologists and auditory science researchers, practices which fail to recognize the existence of any asymmetry in the HAS. The model described here suggests a clear need for: “asymmetry sensitive” hearing test tools that provide normative data for the lifespan, closer childhood and aging-adult hearing monitoring, and the development of a range of auditory training modules. Notably, the model suggests that without such tools our HAS asymmetry knowledge will remain incomplete. The status quo is a preoccupation with understanding hearing through knowledge of the peripheral hearing system, no answers for those with a “normal audiogram” but with an obvious difficulty hearing speech-in-noise, limited success cochlear implant rehabilitation, and missed opportunities to successfully intervene with childhood hearing/speech/language development problems.

Highlights

The progress of audiological rehabilitation and auditory science research remains compromised by the continuing preoccupation with understanding hearing through knowledge of the peripheral hearing system [Hewitt, 2018; Musiek et al, 2017]
When the depth of our knowledge of the central auditory system matches that of the peripheral auditory system, and audiological practice is informed by the integration of this knowledge, can we expect to properly rehabilitate those with hearing problems
While some asymmetry exists at birth, it is life experience that shapes the detail of the auditory processing capability and the functional asymmetry of an individual’s auditory system

Summary

Introduction

The progress of audiological rehabilitation and auditory science research remains compromised by the continuing preoccupation with understanding hearing through knowledge of the peripheral hearing system [Hewitt, 2018; Musiek et al, 2017]. They suggest that brain lateralization depends upon fast inter-hemispheric transfer, and that the corpus callosum has an important role in the processing of binaural cues and spatial hearing In their recent review of the white matter asymmetries of the nervous system Ocklenburg et al [2016] concluded that, further investigation is still needed to understand the detail of the pathways and the inhibition and excitation involved, the hemispheric functional asymmetries depend upon the CC and its maturation path. The review by Musiek & Weihing [2011] reports that the worsening of left ear scores in dichotic listening tests begins in the middle of the sixth decade, as the corpus callosum begins to reduce in size (see Figure 4)

Discussion

Conclusion