title: Effects of age and background noise on processing a mistuned harmonic in an otherwise periodic complex sound.
abstract: Older adults presented with short (i.e., 40 ms) harmonic complex tones show a reduced likelihood of hearing the mistuned harmonic as a separate sound. Here, we examined whether this age difference for the mistuned harmonic would generalize to a longer signal duration (i.e., 200 ms). We measured auditory evoked fields (AEFs) using magnetoencephalography while young and older adults were presented with harmonic complex tones that either had all partials of the tones in tune (single sound object) or contained a 4 or 16% mistuned harmonic (dual sound objects). The auditory stimuli were presented in isolation or embedded in low or moderate levels of continuous white noise. For each participant, we modeled the AEFs with a pair of dipoles in the superior temporal plane and examined the effects of age and noise on the amplitude and latency of the resulting source waveforms. The present study reveals similar noise-induced increases in N1m and object-related negativity in young and older adults which may be mediated via efferent feedback connections and/or changes in the temporal window of integration. We observed less age-related differences in concurrent sound segregation for stimuli that matched the duration of the temporal integration window of auditory perception (i.e., ∼200 ms) than for short duration sounds (i.e., 40 ms). Possible explanations for this duration-dependent age-related decline in concurrent sound perception are a general slowing in auditory processing and/or lengthening of the temporal integration window.
authors.affiliation: Rotman Research Institute, Baycrest Centre for Geriatric Care, 3560 Bathurst Street, Toronto, Ontario, Canada M6A 2E1. calain@rotman-baycrest.on.ca
authors.forename: Claude
authors.initials: C
authors.lastname: Alain
authors.forename: Kelly
authors.initials: K
authors.lastname: McDonald
authors.forename: Patricia
authors.initials: P
authors.lastname: Van Roon
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D001301:Audiometry, Pure-Tone; D001302:Audiometry, Speech; D001306:Auditory Pathways / Q000502:physiology*; D001307:Auditory Perception; D001309:Auditory Threshold; D005072:Evoked Potentials, Auditory; D030141:Feedback, Psychological; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects*; D010470:Perceptual Masking; D011571:Psychoacoustics; D011930:Reaction Time; D013067:Speech Perception; D013997:Time Factors; D055815:Young Adult