Sustained responses and neural synchronization to amplitude and frequency modulation in sound change with age

Abstract

Perception of speech requires sensitivity to features, such as amplitude and frequency modulations, which are often temporally regular. Previous work suggests age-related changes in neural responses to temporally regular features, but little work has focused on age differences for different types of modulations. We recorded magnetoencephalography in younger (21–33 years) and older adults (53–73 years) to investigate age differences in neural responses to slow (2-6 Hz sinusoidal and non-sinusoidal) modulations in amplitude, frequency, or combined amplitude and frequency. Neural responses to sound onset (independent of temporal modulations) were enhanced in older compared to younger adults, suggesting hyperresponsivity and a loss of inhibition in the aged auditory system. Analyses of neural activity to modulations revealed enhanced neural synchronization with amplitude, frequency, and combined amplitude-frequency modulations for older compared to younger adults. This enhancement generalized across different degrees of temporal regularity (sinusoidal and non-sinusoidal), although neural synchronization was generally lower for non-sinusoidal modulation. Despite enhanced synchronization, sustained neural activity was reduced in older compared to younger adults for sounds modulated both sinusoidally and non-sinusoidally in frequency. Our results suggest substantial age differences in the sensitivity of the auditory system to features present in speech and other natural sounds.

Neural signatures of task-related fluctuations in auditory attention change with age

“…Hearing thresholds for the white-noise sound used in the current study were about 6.5 dB higher for older adults compared to younger adults (t 50 = 5.539, p = 1.1 × 10 −6 ). A threshold difference of 6.5 dB is in line with previous studies that compared younger and older adults with clinically ‘normal’ audiometry thresholds (Herrmann et al, 2018, 2022b, a). Finally, to account for any potential differences due to subclinical hearing impairment, sounds were presented at 45 dB above the individual hearing threshold (equating for audibility) and the gap duration was titrated for each participant (equating for task performance/difficulty).…”