Age-related processing delay reveals cause of apparent sensory excitability following auditory stimulation

Márta Volosin,János Horváth,Zsófia Anna Gaál

doi:10.1038/s41598-017-10696-1

Abstract

When background auditory events lead to enhanced auditory event-related potentials (ERPs) for closely following sounds, this is generally interpreted as a transient increase in the responsiveness of the auditory system. We measured ERPs elicited by irrelevant probes (gaps in a continuous tone) at several time-points following rare auditory events (pitch glides) in younger and older adults, who watched movies during stimulation. Fitting previous results, in younger adults, gaps elicited increasing N1 auditory ERPs with decreasing glide-gap separation. N1 increase was paralleled by an ERP decrease in the P2 interval. In older adults, only a glide-gap separation dependent P2 decrease, but no N1-effect was observable. This ERP pattern was likely caused by a fronto-central negative waveform, which was delayed in the older adult group, thus overlapping N1 and P2 in the younger, but overlapping only P2 in the older adult group. Because the waveform exhibited a polarity reversal at the mastoids, it was identified as a mismatch negativity (MMN). This interpretation also fits previous studies showing that gap-related MMN is delayed in older adults, reflecting an age-related deterioration of fine temporal auditory resolution. These results provide a plausible alternative explanation for the ERP enhancement for sounds following background auditory events.

Highlights

When absorbed in a task, task-irrelevant stimuli seem to fade into the background
The goal of the present study was to compare the duration of a distracted state induced by randomly occurring rare, background auditory events between younger and older adults
While participants watched a silent movie with subtitles, continuous tones containing rare glides and frequent gaps were presented

Summary

Introduction

When absorbed in a task, task-irrelevant stimuli seem to fade into the background. Moments of such immersion still do not provide a complete isolation from the stimulus environment: sudden changes in the acoustic background still capture our attention, even if they are irrelevant to the ongoing behavior. In the active version of the paradigm, participants’ task was to respond to gaps by pressing a button Due to their infrequency and unpredictability, the glides functioned as distracters in these paradigms: Horváth, Volosin, Grimm, and Horváth found that rare glides elicited a higher N1 than frequent glides (and possibly an MMN), but no P3a. Gaps following rare glides in 150 ms elicited lower-amplitude N1s in comparison to gaps following glides by 650 ms (see Schröger36), or in comparison to gaps without closely preceding glides28 This impacted auditory processing suggests that 150 ms after the distracter onset the task-optimal attention set for gap-detection was not yet reinstated. Due to their temporally different unfolding, facilitation dominates till about 400 ms, after which inhibition becomes dominant

Objectives

Methods

Results

Conclusion