title: Evidence of "hidden hearing loss" following noise exposures that produce robust TTS and ABR wave-I amplitude reductions.
abstract: In animals, noise exposures that produce robust temporary threshold shifts (TTS) can produce immediate damage to afferent synapses and long-term degeneration of low spontaneous rate auditory nerve fibers. This synaptopathic damage has been shown to correlate with reduced auditory brainstem response (ABR) wave-I amplitudes at suprathreshold levels. The perceptual consequences of this "synaptopathy" remain unknown but have been suggested to include compromised hearing performance in competing background noise. Here, we used a modified startle inhibition paradigm to evaluate whether noise exposures that produce robust TTS and ABR wave-I reduction but not permanent threshold shift (PTS) reduced hearing-in-noise performance. Animals exposed to 109 dB SPL octave band noise showed TTS >30 dB 24-h post noise and modest but persistent ABR wave-I reduction 2 weeks post noise despite full recovery of ABR thresholds. Hearing-in-noise performance was negatively affected by the noise exposure. However, the effect was observed only at the poorest signal to noise ratio and was frequency specific. Although TTS >30 dB 24-h post noise was a predictor of functional deficits, there was no relationship between the degree of ABR wave-I reduction and degree of functional impairment.
authors.affiliation: The University of Texas at Dallas, School of Behavioral and Brain Sciences, USA. Electronic address: Edward.Lobarinas@utdallas.edu.
authors.forename: Edward
authors.initials: E
authors.lastname: Lobarinas
authors.affiliation: University of Mississippi Medical Center, Department of Otolaryngology and Communicative Sciences, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Spankovich
authors.affiliation: The University of Texas at Dallas, School of Behavioral and Brain Sciences, USA.
authors.forename: Colleen G
authors.initials: CG
authors.lastname: Le Prell
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001305:Auditory Fatigue; D001522:Behavior, Animal; D001933:Brain Stem / Q000503:physiopathology*; D003463:Cues; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem; D006317:Hearing Loss, Noise-Induced / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D008297:Male; D009622:Noise / Q000009:adverse effects*; D017084:Otoacoustic Emissions, Spontaneous; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle; D013997:Time Factors
keywords: Hearing-in-noise; Hidden hearing loss; Noise exposure; Startle inhibition; Synaptopathy