Ageing impacts basic auditory and timing processing

Abstract

Deterioration in the peripheral and central auditory systems is common in older adults and often leads to hearing and speech comprehension difficulties. Even when hearing remains intact, electrophysiological data of older adults frequently exhibit altered neural responses along the auditory pathway, reflected in variability in phase alignment of neural activity to speech sound onsets. However, it remains unclear whether these challenges in speech processing in aging stem from more fundamental deficits in auditory and timing processes. Here, we investigated if and how aging individuals encoded temporal regularities in isochronous auditory sequences presented at 1.5Hz, and if they employed adaptive mechanisms of neural phase alignment in anticipation of next sound onsets. We recorded EEG in older and young individuals listening to simple isochronous tone sequences. We show that aging individuals displayed increased amplitudes and variability in time-locked responses to sounds, an increased 1/F slope, but reduced phase-coherence in the delta and theta frequency-bands. These observations suggest a lack of repetition-suppression and inhibition when processing repeated and predictable sounds in a sequence and altered mechanisms of continuous phase-alignment to expected sound onsets in aging. Given that deteriorations in these basic timing capacities may affect other higher-order cognitive processes (e.g., attention, perception, and action), these results underscore the need for future research examining the link between basic timing abilities and general cognition across the lifespan. HighligthsO_LIAging individuals (HO) show increased cortical excitability as compared to younger adults (HY); C_LIO_LIHOs neural responses to fully predictable isochronous tones were larger and more variable than HY; C_LIO_LIHO showed reduced phase coherence in delta- and theta-band oscillations during listening to auditory sequence; C_LIO_LIAltogether, these results show altered sensory and timing processes in aging. C_LI