Abstract
An extensive corticofugal system extends from the auditory cortex
toward subcortical nuclei along the auditory pathway. Corticofugal
influences reach even into the inner ear via the efferents of the
olivocochlear bundle, the medial branch of which modulates preneural
sound amplification gain. This corticofugal system is thought to
contribute to neuroplasticity underlying auditory perceptual learning.
In the present study, we investigated the involvement of the medial
olivocochlear bundle (MOCB) in perceptual learning as a result of
auditory training. MOCB activity was monitored in normal-hearing
adult listeners during a 5 d training regimen on a consonant-vowel
phoneme-in-noise discrimination task. The results show significant
group learning, with great inter-individual variability in initial
performance and improvement. As observed in previous auditory training
studies, poor initial performers tended to show greater learning.
Strikingly, MOCB activity measured on the first training day strongly
predicted the subsequent amount of improvement, such that weaker
initial MOCB activity was associated with greater improvement. Moreover,
in listeners that improved significantly, an increase in MOCB activity
was observed after training. Thus, as discrimination thresholds of
listeners converged over the course of training, differences in MOCB
activity between listeners decreased. Additional analysis showed
that MOCB activity did not explain variation in performance between
listeners on any training day but rather reflected an individual
listener's performance relative to their personal optimal range.
The findings suggest an MOCB-mediated listening strategy that facilitates
speech-in-noise perception. The operation of this strategy is flexible
and susceptible to training, presumably because of task-related adaptation
of descending control from the cortex.
- adult,auditory
- analysis,teaching
- and
- discrimination
- nucleus,cochlear
- nucleus,olivary
- nucleus:
- pathways,efferent
- pathways:
- perception,auditory
- perception,speech
- perception:
- performance
- physiology,cochlear
- physiology,efferent
- physiology,female,humans,learning,learning:
- physiology,noise,olivary
- physiology,speech
- physiology,task
- tests,speech
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