Cortical sensory gating and reactions to dynamic speech-in-noise in older normal-hearing and hearing-impaired adults.

Abstract

Objective: To examine whether cortical sensory gating predicts how older adults with and without hearing loss perform the Tracking of Noise Tolerance (TNT) test.

Design: Single-blind mixed design. TNT performance was defined by average tolerated noise relative to speech levels (TNT_Ave) and by an average range of noise levels over a two-minute trial (excursion). Sensory gating of P1-N1-P2 components was measured using pairs of 1 kHz tone pips.

Study sample: Twenty-three normal-hearing (NH) and 16 hearing-impaired (HI) older adults with a moderate-to-severe degree of sensorineural hearing loss.

Results: NH listeners tolerated significantly more noise than HI listeners, but the two groups did not differ in their excursion. Both NH and HI listeners exhibited significant gating of P1 amplitudes and N1P2 peak-to-peak amplitudes with no difference in gating magnitudes between listener groups. Sensory gating magnitudes of P1 and N1P2 did not predict TNT_Ave scores, but N1P2 gating negatively predicted excursion after accounting for listener age and hearing thresholds.

Conclusions: Listeners' reactivity to a roving noise (excursion), but not their average noise tolerance (TNT_Ave), was predicted by sensory gating at N1P2 generators. These results suggest that temporal aspects of speech-in-noise processing may be affected by declines in the central inhibition of older adults.