Human Envelope Following Responses to Amplitude Modulation: Effects of Aging and Modulation Depth.
Andrew Dimitrijevic, Jamal Alsamri, M Sasha John and 3 others
PMID 27556365WHAT IT FOUND
Older adults did not differ from young adults in detecting loudness fluctuations.
The oldest adults’ brain responses changed shape and timing as fluctuations increased, and brain-response thresholds tracked detection ability.
Key findings
01Brain responses to a changing loudness fluctuation did not differ from brain responses to fixed loudness fluctuation levels.
02The minimum loudness fluctuation that produced a measurable brain response was related to the minimum loudness fluctuation participants could detect.
03Older adults’ behavioral detection thresholds did not differ, but their brain responses reached half-maximum at lower loudness fluctuations and covered a narrower range of fluctuation levels.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The groups were small, with 12 per age group, and only 24 participants completed the fixed-depth condition. The older groups had elevated pure-tone thresholds, so aging and hearing loss were not separated. The study did not measure speech perception in quiet or noise, so it cannot show whether these responses relate to speech perception. Two participants were removed because of incomplete testing or muscle artifact, which would often require retesting in clinic. Three oldest participants had unusually large EFR amplitudes. Excluding them changed the linearity result, so that result was sensitive to outliers. The correlation between behavioral and EFR thresholds was r=0.48, p=0.003, and behavioral thresholds had limited variation, so EFRs may not replace behavioral testing.
The easy way to misread this
Do not conclude that these brain-response differences explain older adults’ speech-in-noise problems. The study did not measure speech perception, and behavioral AM detection thresholds did not differ between groups.