Many older subjects experience difficulty in understanding speech in noisy environments.
Part of this problem is related to changes that occur in the ear with age and compromise the
hearing of high-pitched sounds. Another part of the problem with speech understanding
relates to changes with age in the neural circuits of the brain that process different
speech sounds. Evidence suggests that these changes in neural circuits are particularly
large if hearing loss is present. Thus, while hearing aids may help compensate for hearing
deficits by amplifying speech sounds, additional treatment is necessary to restore optimal
neural connections in the brain so that speech sounds can be accurately distinguished from
each other. We are developing PC-based training programs in an attempt to restore optimal
neural connections. The current randomized trial will evaluate whether two months of
training to improve the ability to discriminate different consonant sounds in noise will
also improve the understanding of continuous speech and enhance auditory memory and other
high-level auditory functions.
More than 300,000 veterans with sensorineural hearing loss (SNHL) are fitted with VA-issued
hearing aids (HAs) each year with the primary goal of improving their understanding of
speech. Even older veterans without hearing loss experience a gradual decline in speech
discrimination due to age-related changes in auditory function that compromise speech
understanding in everyday environments. Neuroplastic reorganization within the central
auditory system due to SNHL and aging contribute to these effects and compromise subjects'
ability to process phonetic cues that are essential for understanding speech in noise. As a
consequence, even when a HA restores high frequency signals to the cochlea in a patient with
SNHL, speech understanding will remain suboptimal in the absence of rehabilitative
We have developed perceptual learning paradigms that drive this rehabilitative
reorganization and significantly improve speech discrimination in new HA users. We now
propose to test improved training paradigms in new and experienced HA users and older
subjects with normal hearing. In Exp. 1 we will evaluate baseline speech discrimination in
these populations using speech-reception thresholds (SRTs) in sentences,
consonant-vowel-consonant nonsense syllable tests (CVC-NST), tests of tone-pattern
discrimination, and tests of auditory short-term verbal memory (ASTVM). An analysis of the
correlations of these measures will provide information about basic processes underlying
impaired word and sentence identification. In Exp. 2 we will investigate the effects of
CVC-identification training using performance-adapted masking noise. Based on our previous
results, we anticipate that training will significantly improve CVC-NST scores. We will
examine the extent to which training improves SRTs, tone-pattern processing, and ASTVM. In
Exp. 3 we will train subjects in a tone-pattern identification task to evaluate the extent
to which non-phonetic factors (e.g., familiarity with the computerized hearing tests,
placebo effects of training, improvements in auditory attention, etc.) may contribute to
training benefit. In Exp. 4 we will compare the benefits of training with single-consonant
syllables with the benefits of two-consonant syllable training studied in Exp. 2. Finally,
in Exp. 5 we will study the benefits of CVC training using consonant-specific noise levels
adjusted to compensate for intrinsic differences in the discriminability of different
consonants and compare them to the benefits of global adaptive training from Exp. 2. The
experiments will clarify fundamental mechanisms underlying deficits in speech discrimination
and ASTVM, provide insight into the nature of training-related improvements, and elucidate
the parameters needed to optimize hearing rehabilitation.
Relevance to the VA patient care mission: HAs are relatively ineffective in improving the
ability of hearing-impaired subjects to understand speech in many everyday listening
situations. These experiments will clarify the extent to which perceptual training can
improve speech discrimination and enhance ASTVM in these conditions in new and experienced
HA users and older subjects with normal hearing. Perceptual training could potentially
benefit millions of veterans who wear HAs as well as older veterans with normal hearing who
experience difficulties in understanding and remembering speech.
- Older subjects with normal hearing.
- Older subjects with mild sensorineural hearing loss who have recently received
- Some young subjects with normal hearing for developing training paradigms.
- Health problems that would preclude training.