Quantifying the Impact of Auditory Deafferentation on Speech Perception.
Jiayue Liu, Joshua Stohl, Enrique A Lopez-Poveda and 1 others
PMID 38291713WHAT IT FOUND
Simulated hearing nerve damage showed that speech perception in noise worsens significantly only when 90% or more of the auditory nerve connections are lost.
This explains why patients with normal hearing tests can struggle in noise without having obvious nerve damage from aging.
Key findings
01Speech perception in noise deteriorated significantly only at modeled auditory deafferentation levels of 90% or higher, while lower levels had no differential effect compared to quiet.
02Normal aging typically causes a loss of one-third to two-thirds of auditory nerve fibers, which is substantially less than the 90% loss required to produce the simulated deficits in speech-in-noise perception.
03The study used a computational model to simulate nerve loss and tested how well human participants could perceive speech reconstructed by this model, rather than testing actual patients with diagnosed nerve damage.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used a computational model to simulate nerve damage, not actual patients with diagnosed auditory neuropathy or synaptopathy. The model assumed the brain optimally processes the degraded signal, which may underestimate the true difficulty experienced by humans with hearing loss. The model did not account for central nervous system changes (like hyper-synchronization) that occur with nerve loss, which could worsen perception. Online testing introduced variability in audio equipment and participant environments, though calibration steps were taken. The participants were generally young to middle-aged adults with normal hearing, so results may not directly apply to older adults with presbycusis.
Declared interests
The authors declared no potential conflicts of interest. The work was supported by the Charles Lafitte Foundation.
The easy way to misread this
Do not conclude that auditory nerve fiber loss is the primary cause of speech-in-noise difficulties in older adults. The study shows that natural aging causes much less nerve loss (one-third to two-thirds) than the 90% loss required to produce the specific deficits seen in the model.