Effect of aging on the click-rate induced facilitation of acoustic reflex thresholds

Acoustic reflex thresholds are known to improve with an increase in the click-repetition rates from 50/sec to 300/sec. In the current study this improvement was used to evaluate auditory processing in older subjects. Acoustic reflex thresholds were obtained from 16 human adult ears within each of the following four groups: young male, young female (18-28 years), older male and older female (50-65 years). The probe tone frequency was 226 Hz and the intensity of the probe tone was 85 dB SPL (sound pressure level). Clicks were delivered ipsilaterally to each ear at repetition rates of 50, 100, 150, 200, and 300/sec. The mixed MANOVA revealed a significant effect for the repetition rate and a significant age and rate interaction. Rate integration in dB was computed by subtracting the highest acoustic reflex threshold from the lowest threshold of each ear. Statistical analyses revealed reduced rate integration in the older subjects, suggesting less efficient processing of faster stimuli within the acoustic reflex pathway.