Noise-induced hearing loss alters the temporal dynamics of auditory-nerve responses

Abstract

Auditory-nerve fibers demonstrate dynamic response properties in that they adapt to rapid changes in sound level, both at the onset and offset of a sound. These dynamic response properties affect temporal coding of stimulus modulations that are perceptually relevant for many sounds such as speech and music. Temporal dynamics have been well characterized in auditory-nerve fibers from normal-hearing animals, but little is known about the effects of sensorineural hearing loss on these dynamics. This study examined the effects of noise-induced hearing loss on the temporal dynamics in auditory-nerve fiber responses from anesthetized chinchillas. Post-stimulus time histograms were computed from responses to 50-ms tones presented at characteristic frequency and 30 dB above fiber threshold. Several response metrics related to temporal dynamics were computed from post-stimulustime histograms and were compared between normal-hearing and noise-exposed animals. Results indicate that noise-exposed auditory-nerve fibers show significantly reduced response latency, increased onset response and percent adaptation, faster adaptation after onset, and slower recovery after offset. The decrease in response latency only occurred in noise-exposed fibers with significantly reduced frequency selectivity. These changes in temporal dynamics have important implications for temporal envelope coding in hearing-impaired ears, as well as for the design of dynamic compression algorithms for hearing aids.

Physiological, anatomical, and behavioral changes after acoustic trauma in Drosophila melanogaster

“…Gunshot noise trauma delayed guinea pig CAPs by ∼50-200 μs compared with controls (13). Conversely, other studies found reduced latencies of single AN fibers in response to acute noise (28,30,31,35). Latency reductions are probably due to the particular mammalian cochlea mechanical tonotopy and tuning properties.…”

Computational Modeling of Individual Differences in Behavioral Estimates of Cochlear Nonlinearities

“…For subjects in the mid and high threshold groups, poor detection efficiency does not necessarily indicate a deficit of the central auditory system but may suggest a peripheral degradation of important cues that cannot be resolved by the central detector. The degree to which detection efficiency is compromised by peripheral degradation of detection cues is unknown, as are the sources of this degradation; however, these sources may be related to poorer frequency resolution (e.g., Sellick et al 1982) or altered neural adaptation (Scheidt et al 2010). Peripheral degradation of detection cues may also contribute to increased individual differences among hearing-impaired listeners, as compared to normal-hearing listeners, in TMCs and other psychophysical and speech perception tasks (e.g., Moore 2007).…”

Perception of Across-Frequency Asynchrony by Listeners with Cochlear Hearing Loss

“…Because cochlear hearing loss is associated with broadening of peripheral auditory filters due to the loss of cochlear gain, the effect of hearing loss on the cochlear latency-frequency function should be similar to the effect of a high stimulus level. A recent physiological study by Scheidt et al (2010) reported that response latencies in the AN of anesthetized chinchillas with noise-induced hearing loss were shorter than those in the normal-hearing animals, but only in fibers that showed broader tuning in addition to threshold elevation after the noise exposure. The decrease in latency was about 0.5 ms, similar to that shown by the postmortem data in the study by Ruggero and Temchin (2007).…”

“…Unfortunately, the hearing loss in the study by Scheidt et al (2010) was induced using a bandpass noise extending from 1 to 4 kHz, and thus, thresholds were elevated over a limited frequency range that did not include CFs below 1 kHz. For humans, the latency-frequency functions estimated from derivedband ABRs measured in the study by Don et al (1998) suggest that hearing loss in the apical region results in a greater decrease in response latency than that in the basal region of the cochlea.…”

“…Broader filters may also result in shortened response delays in the regions of the cochlea affected by the damage. Indeed, direct recordings from AN fibers have shown that cochlear impairment results in reduced response times (Wang and Dallos 1972;Dallos and Harris 1978;Salvi et al 1979;Heinz et al 2010;Scheidt et al 2010). An important question is whether cochlear hearing loss affects the slope of the cochlear latencyfrequency function in ways that may alter the perception of across-frequency timing information.…”