Age differences in the neuroelectric adaptation to meaningful sounds.

Ada W S Leung,Claude Alain,Cheryl L Grady,Yu He,Trevor Bruce Penney

doi:10.1371/journal.pone.0068892

Ada W S Leung, Claude Alain + Show 3 more

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https://doi.org/10.1371/journal.pone.0068892

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Abstract

Much of what we know regarding the effect of stimulus repetition on neuroelectric adaptation comes from studies using artificially produced pure tones or harmonic complex sounds. Little is known about the neural processes associated with the representation of everyday sounds and how these may be affected by aging. In this study, we used real life, meaningful sounds presented at various azimuth positions and found that auditory evoked responses peaking at about 100 and 180 ms after sound onset decreased in amplitude with stimulus repetition. This neural adaptation was greater in young than in older adults and was more pronounced when the same sound was repeated at the same location. Moreover, the P2 waves showed differential patterns of domain-specific adaptation when location and identity was repeated among young adults. Background noise decreased ERP amplitudes and modulated the magnitude of repetition effects on both the N1 and P2 amplitude, and the effects were comparable in young and older adults. These findings reveal an age-related difference in the neural processes associated with adaptation to meaningful sounds, which may relate to older adults’ difficulty in ignoring task-irrelevant stimuli.

Highlights

Auditory adaptation refers to the reduction of neural responses when a sound is heard repetitively within a period of several seconds [1,2]
Neural adaptation reflects a process by which the brain encodes stimulus invariance and likely occurs because of neural refractoriness in which a neuron can only respond to a stimulus after a sufficient period of recovery following a response to a preceding stimulus [4,5]
Effect of age on the adaptation of N1 amplitude Repeated measures ANOVA revealed main effects of age, F(1,22) = 4.363; p = 0.049, noise condition, F(1,22) = 17.415; p < 0.001, and position, F(3,66) = 14.912; p < 0.001, and a significant interaction effect between noise condition and position, F(3,66) = 16.409; p < 0.001. This interaction was caused by markedly reduced N1 amplitudes from the first to the second sound of the sequence when the stimuli were not embedded in noise (Figures 2 and 3)

Summary

Introduction

Auditory adaptation refers to the reduction of neural responses when a sound is heard repetitively within a period of several seconds [1,2]. Other studies have shown reduced P2 amplitudes (positive wave peaking at about 180 ms post-stimulus) for sounds coming from identical spatial locations [9]. These patterns of neural adaptation have been related to increased cognitive efficiency, such as improved stimulus identification [10], auditory memory [11], and rapid learning [7]

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