Brainstem correlates of cochlear nonlinearity measured via the scalp-recorded frequency-following response. Issue 10 (10th July 2020)

• Record Type: Journal Article
• Authors: Bidelman, Gavin M.; Bhagat, Shaum
• Is Part Of: NeuroReport. Volume 31:Issue 10(2020)
• Publication Date: 2020-07-10
• Subjects: auditory brainstem response -- cochlear nonlinearity -- distortion product otoacoustic emission -- hidden hearing loss -- synaptopathy; Neurosciences -- Periodicals; Nervous system -- Periodicals; Neurophysiology -- Periodicals; Nervous System Diseases -- Periodicals; Nervous System Physiological Phenomena -- Periodicals; Neurosciences -- Periodicals; 616.805
• DOI: 10.1097/WNR.0000000000001452
• Languages: English
• ISSNs: 0959-4965

Abstract

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. Abstract : Supplemental Digital Content is available in the text.