Understanding Aided Speech Perception in Noise: Behavioral and Electrophysiological Measures
The overarching hypothesis to be evaluated using this protocol is that age-related hearing loss (ARHL) leads to shifts in the functional spatial boundaries between segregated and integrated auditory streams, and that hearing aid intervention that relies on directional processing schemes is most effective for those that have the poorest spatial sensitivity. One key component of the research design is to measure both behavioral and neurophysiological indices of an individual's spatial segregation boundary. The second key component is to measure the cost or benefit associated with hearing aid intervention in older hearing-impaired listeners. The final component is to relate cost and benefit of hearing aid intervention to spatial sensitivity measures that might predict the efficacy of clinical intervention.
⁃ Target candidates for this study will be 38 young normal-hearing (YNH), 38 older normal-hearing (ONH), and 55 older hearing-impaired (OHI) subjects. Eligible NH listeners will have ≤20 dB HL at octave frequencies from 0.25 to 4 kHz and ≤30 dB HL up to 8 kHz. Eligible HI listeners will have bilateral (symmetric), moderate sensorineural hearing loss characterized by pure-tone thresholds between 35 to 50 dB HL from 0.25 to 2 kHz and 50 to 70 dB HL between 3 and 8 kHz. Age is restricted from 60 to 80 years for the older listening groups and from 18 to 35 for younger listeners. A balance of male and female participants will be recruited to assess sex as a biological variable in the data analyses. This age range for older listeners was chosen to be maximally inclusive of potential presbycusic participants, to promote generality of the results, and to facilitate uniform sampling within this age range. The investigators want to avoid the scientific need to stratify by age, which would make the scope of the project unmanageable given the constraints of this five-year award. The investigators have no evidence that lower or higher ages would affect aided intervention. Thus, inclusion of a larger age range would weaken the rigor of the investigation and complicate interpretation of the findings. The target range of hearing loss was chosen for similar reasons, reflecting the largest segment of older adults with hearing loss while avoiding the need to stratify by hearing loss to evaluate the stated hypotheses.
⁃ Additional Inclusion Criteria for HI group:
• Bilateral sensorineural hearing losses within the mild-to-moderately severe range as indicated by pure tone air- and bone-conduction audiometry and screening (Y-226 Hz, Type A) tympanograms.
• Candidates for hearing aids or experienced users.
• Fluent speaker of English as speech testing will be in English.
• MoCA (Montreal Cognitive Assessment; Nasreddine et al., 2005) score of \> 22. This cut point has been used frequently in investigations of aging and will better ensure that cognitive related problems will not restrict the abilities of subjects to perform the study tasks.