Neuroplasticity in Auditory Aging_Project 2

The detrimental effects of aging on auditory temporal processing have been well documented in
humans and animal models. At present, there are gaps in knowledge of the extent to which
these auditory temporal processing deficits can be mitigated in older adults with or without
hearing loss through auditory training and neuroplasticity, to improve precision of neural
timing and speech understanding. The long-term goal is to determine the extent to which
hearing deficits in older adults can be ameliorated with auditory training. The investigators
propose an innovative approach to the investigation of aging, hearing, and neuroplasticity by
marrying perceptual training experiments with electrophysiological measurements. The
objectives are to compare young normal-hearing (YNH), older normal-hearing (ONH), and older
hearing-impaired (OHI) adult listeners, and evaluate the improvements in perceptual and
electrophysiological measures of temporal processing after explicit training on auditory
temporal processing tasks. The central hypothesis is that training of auditory temporal
processing will produce concomitant improvements in both perceptual performance and neural
encoding, which will close the gap in the age-related differences between groups. The central
hypothesis will be tested by pursuing three specific aims: (1) Determine the extent to which
perceptual training on temporal rate discrimination using simple non-speech stimuli improves
perceptual and neural encoding in YNH, ONH, and OHI listeners; (2) Determine the extent to
which perceptual training on speech cue discrimination in contrasting words differing in
discrete temporal cues improves perceptual and neural encoding in YNH, ONH, and OHI
listeners; and (3) Determine the extent to which perceptual training on the processing of
sentences with increasing presentation rate can improve behavioral performance and neural
encoding in YNH, ONH, and OHI listeners. The expected outcomes are that the investigators
will learn what perceptual training tasks lead to simultaneous improvements in perceptual and
neural auditory temporal processing and the findings will produce a significant impact in
older listeners who experience difficulty in communicating in daily life because they will
lead directly to focused and novel forms of rehabilitation. This research is innovative
because the investigators will have established techniques that are proven to provide
significant improvements in auditory temporal processing and speech perception, combined with
evidence of improvements to neural encoding. These studies will serve the larger goals of the
program project grant because they will help identify the neuroplastic mechanisms in the
brain of humans that correspond to successful behavioral outcomes in younger and older
adults.

Inclusion Criteria:

- native speaker of English

- normal cognitive function as measured on Montreal Cognitive Assessment

- pass screening auditory brainstem response test to make sure they have recordable
brainwaves to acoustic stimuli

- age and hearing sensitivity:

- young normal-hearing listeners, 18-35 years, hearing thresholds less than 25 decibels
(dB) HL from 250 - 4000 Hz;

- older normal-hearing listeners, 65-85 years, hearing thresholds less than 25 dB HL,
from 250-4000 Hz;

- older hearing-impaired listeners, 65-85 years, with mild-to-moderate, high frequency
sensorineural hearing loss;

- high school diploma

Exclusion Criteria:

- absence of conductive hearing loss and middle-ear disease

- no neurological disease

- severe or profound hearing loss

- non-native speaker of English

- cognitive impairment