title: Sensorineural hearing loss amplifies neural coding of envelope information in the central auditory system of chinchillas.
abstract: People with sensorineural hearing loss often have substantial difficulty understanding speech under challenging listening conditions. Behavioral studies suggest that reduced sensitivity to the temporal structure of sound may be responsible, but underlying neurophysiological pathologies are incompletely understood. Here, we investigate the effects of noise-induced hearing loss on coding of envelope (ENV) structure in the central auditory system of anesthetized chinchillas. ENV coding was evaluated noninvasively using auditory evoked potentials recorded from the scalp surface in response to sinusoidally amplitude modulated tones with carrier frequencies of 1, 2, 4, and 8 kHz and a modulation frequency of 140 Hz. Stimuli were presented in quiet and in three levels of white background noise. The latency of scalp-recorded ENV responses was consistent with generation in the auditory midbrain. Hearing loss amplified neural coding of ENV at carrier frequencies of 2 kHz and above. This result may reflect enhanced ENV coding from the periphery and/or an increase in the gain of central auditory neurons. In contrast to expectations, hearing loss was not associated with a stronger adverse effect of increasing masker intensity on ENV coding. The exaggerated neural representation of ENV information shown here at the level of the auditory midbrain helps to explain previous findings of enhanced sensitivity to amplitude modulation in people with hearing loss under some conditions. Furthermore, amplified ENV coding may potentially contribute to speech perception problems in people with cochlear hearing loss by acting as a distraction from more salient acoustic cues, particularly in fluctuating backgrounds.
authors: Weldon School of Biomedical Engineering, Purdue University, 206 South Martin Jischke Drive, West Lafayette, IN 47907, USA.
authors: Ziwei
authors: Z
authors: Zhong
authors: Department of Speech, Language, and Hearing Sciences, Purdue University, 500 Oval Drive, West Lafayette, IN 47907, USA.
authors: Kenneth S
authors: KS
authors: Henry
authors: Weldon School of Biomedical Engineering, Purdue University, 206 South Martin Jischke Drive, West Lafayette, IN 47907, USA; Department of Speech, Language, and Hearing Sciences, Purdue University, 500 Oval Drive, West Lafayette, IN 47907, USA. Electronic address: mheinz@purdue.edu.
authors: Michael G
authors: MG
authors: Heinz
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000503:physiopathology*; D001306:Auditory Pathways / Q000503:physiopathology; D001307:Auditory Perception; D001309:Auditory Threshold; D001931:Brain Mapping / Q000379:methods; D002682:Chinchilla; D003463:Cues; D004195:Disease Models, Animal; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D006317:Hearing Loss, Noise-Induced / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D006319:Hearing Loss, Sensorineural / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D009622:Noise; D010470:Perceptual Masking; D011930:Reaction Time; D013997:Time Factors