Amplification Effects on the Acoustic Change Complex in Older Adults With Sensorineural Hearing Loss

Abstract

Purpose: This pilot study evaluated the effect of stimulus level and amplification on the acoustic change complex (ACC) in adults with sensorineural hearing loss. Method: Ten adults with a M age of 74 years and bilaterally symmetrical mild-to-severe sensorineural hearing loss listened to contrasting vowel pairs, while cortical evoked potentials were recorded. The vowel contrasts (/a/−/i/ and /u/−/o/) were presented in the sound field at 30 and 60 dBA. Participants were tested with and without amplification fit to their audiogram configurations. ACC component P1–N1–P2 latencies and P1–N1, N1–P2, and P2–N2 peak-to-trough amplitudes were measured for eight test conditions ([two vowel contrasts] × [two levels] × [aided vs. unaided]). Paired-sample t tests were used to determine the effects of test conditions on ACC component latencies and amplitudes. Results: At 60 dBA, nine of 10 listeners had ACCs in the unaided condition, and the ACC amplitudes were significantly increased in the aided condition for the /a/−/i/ contrast. Amplification did not affect ACC amplitudes for the /u/−/o/ contrast at 60 dBA. At 30 dBA, only three of 10 participants had ACCs present in the aided condition, and none had ACCs in the unaided condition. ACC latencies at 60 dBA were unaffected as a function of amplification, but differences were noted as a function of vowel contrast type. Conclusions: ACCs were obtained for adults with hearing loss, demonstrating the feasibility of measuring a listener's neural capacity to discriminate vowel contrasts. The data indicate promising efficacy for using the ACC to evaluate those who cannot provide reliable perceptual responses, such as in immaturity (infants) or neurocognitive conditions (dementia). The ACC provides evidence of the sensory and neural capacity to detect and discriminate vowel sound contrasts, a neuro-biological validation that can be coupled with electroacoustic verification.