Age Differences in fMRI Adaptation for Sound Identity and Location

Rebecca Charlton,Yu He,Claude Alain,Cheryl L Grady

doi:10.3389/fnhum.2011.00024

Rebecca Charlton, Yu He + Show 2 more

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https://doi.org/10.3389/fnhum.2011.00024

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Abstract

We explored age differences in auditory perception by measuring fMRI adaptation of brain activity to repetitions of sound identity (what) and location (where), using meaningful environmental sounds. In one condition, both sound identity and location were repeated allowing us to assess non-specific adaptation. In other conditions, only one feature was repeated (identity or location) to assess domain-specific adaptation. Both young and older adults showed comparable non-specific adaptation (identity and location) in bilateral temporal lobes, medial parietal cortex, and subcortical regions. However, older adults showed reduced domain-specific adaptation to location repetitions in a distributed set of regions, including frontal and parietal areas, and to identity repetition in anterior temporal cortex. We also re-analyzed data from a previously published 1-back fMRI study, in which participants responded to infrequent repetition of the identity or location of meaningful sounds. This analysis revealed age differences in domain-specific adaptation in a set of brain regions that overlapped substantially with those identified in the adaptation experiment. This converging evidence of reductions in the degree of auditory fMRI adaptation in older adults suggests that the processing of specific auditory “what” and “where” information is altered with age, which may influence cognitive functions that depend on this processing.

Highlights

Neural responses to stimulus repetitions are smaller in magnitude than responses to the first presentation of a stimulus
Young adults show adaptation in a distributed set of brain regions to specific repetitions of the location of a sound, relative to changes in location, and weaker adaptation in temporal cortex when sound identity is repeated, whereas these repetition effects are absent in older adults
Adaptation in medial parietal cortex was seen, in line with activation of this region during processing of sound location (Alain et al, 2001). Adaptation in both temporal identity-sensitive areas and parietal regions sensitive to sound location would be expected in this contrast that examined adaptation to both features

Summary

Introduction

Neural responses to stimulus repetitions are smaller in magnitude than responses to the first presentation of a stimulus. Repetition effects have primarily been studied using electrophysiological responses (e.g., event-related potentials, or ERPs). These consist of reduced amplitude of responses to tones, especially when repetition times are short (Budd et al, 1998; Sable et al, 2004), reductions over minutes (Polich and McIsaac, 1994) and weeks (Shelley et al, 1991) have been observed. Auditory fMRI adaptation has not been as widely studied as that in the visual system, reductions of activity to repeated sounds have been reported to pure tones and noise bursts (Inan et al, 2004; Petkov et al, 2004). Domain-specific adaptation has been reported in anterior temporal cortex for repetition of sound identity, and in posterior temporal cortex and the inferior parietal lobe (IPL) for repetition of a sound’s location (Altmann et al, 2007, 2008)

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