Integrative SystemsBrainstem correlates of cochlear nonlinearity measured via the scalp-recorded frequency-following response.Bidelman, Gavin M.a,,b,,c; Bhagat, Shaumd,,eAuthor Information aInstitute for Intelligent Systems, University of Memphis bSchool of Communication Sciences & Disorders, University of Memphis cDepartment of Anatomy and Neurobiology, University of Tennessee Health Sciences Center, Memphis, Tennessee dDepartment of Communicative Disorders and Sciences eDepartment of Audiology, San Jose State University, San Jose, California, USA Received 19 November 2019 Accepted 18 March 2020 Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website, www.neuroreport.com. Correspondence to Gavin M. Bidelman, PhD, School of Communication Sciences & Disorders, University of Memphis, 4055 North Park Loop, Memphis, TN 38152, USA, Tel: +901 678 5826; fax: +901 525 1282; e-mail: firstname.lastname@example.org NeuroReport: July 10, 2020 - Volume 31 - Issue 10 - p 702-707 doi: 10.1097/WNR.0000000000001452 Buy SDC Metrics Abstract The frequency-following response (FFR) is an EEG-based potential used to characterize the brainstem encoding of complex sounds. Adopting techniques from auditory signal processing, we assessed the degree to which FFRs encode important properties of cochlear processing (e.g. nonlinearities) and their relation to speech-in-noise (SIN) listening skills. Based on the premise that normal cochlear transduction is characterized by rectification and compression, we reasoned these nonlinearities would create measurable harmonic distortion in FFRs in response to even pure tone input. We recorded FFRs to nonspeech (pure- and amplitude-modulated-tones) stimuli in normal-hearing individuals. We then compared conventional indices of cochlear nonlinearity, via distortion product otoacoustic emission (DPOAE) I/O functions, to total harmonic distortion measured from neural FFRs (FFRTHD). Analysis of DPOAE growth and the FFRTHD revealed listeners with higher cochlear compression thresholds had lower neural FFRTHD distortion (i.e. more linear FFRs), thus linking cochlear and brainstem correlates of auditory nonlinearity. Importantly, FFRTHD was also negatively correlated with SIN perception whereby listeners with higher FFRTHD (i.e. more nonlinear responses) showed better performance on the QuickSIN. We infer individual differences in SIN perception and FFR nonlinearity even in normal-hearing individuals may reflect subtle differences in auditory health and suprathreshold hearing skills not captured by normal audiometric evaluation. Future studies in hearing-impaired individuals and animal models are necessary to confirm the diagnostic utility of FFRTHD and its relation to cochlear hearing loss or peripheral neurodegeneration in humans. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.