Neural representation of dynamic frequency is degraded in older adults.
Older adults, even with clinically normal hearing sensitivity, often report difficulty understanding speech in the presence of background noise. Part of this difficulty may be related to age-related degradations in the neural representation of speech sounds, such as formant transitions. Frequency-following responses (FFRs), which are dependent on phase-locked neural activity, were elicited using sounds consisting of linear frequency sweeps, which may be viewed as simple models of formant transitions. Eighteen adults (ten younger, 22-24 years old, and nine older, 51-67 years old) were tested. FFRs were elicited by tonal sweeps in six conditions. Two directions of frequency change, rising or falling, were used for each of three rates of frequency change. Stimulus-to-response cross correlations revealed that older adults had significantly poorer representation of the tonal sweeps, and that FFRs became poorer for faster rates of change. An additional FFR signal-to-noise ratio analysis based on time windows revealed that across the FFR waveforms and rates of frequency change, older adults had smaller (poorer) signal-to-noise ratios. These results indicate that older adults, even with clinically-normal hearing sensitivity, have degraded phase-locked neural representations of dynamic frequency.
Department of Communication Sciences and Disorders, 801 Carrier Drive, MSC 4304, HHS 1128, James Madison University, Harrisonburg, VA 22807, USA. Electronic address: clinarcg@jmu.edu.
Christopher G
CG
Clinard
Department of Communication Sciences and Disorders, 801 Carrier Drive, MSC 4304, HHS 1128, James Madison University, Harrisonburg, VA 22807, USA. Electronic address: cottercm@dukes.jmu.edu.
Caitlin M
CM
Cotter
D000161:Acoustic Stimulation; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000523:psychology*; D001299:Audiometry; D001306:Auditory Pathways / Q000503:physiopathology*; D001309:Auditory Threshold; D032882:Comprehension; D006801:Humans; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects; D010470:Perceptual Masking; D010898:Pitch Perception; D013065:Speech Intelligibility; D013067:Speech Perception; D013997:Time Factors; D055815:Young Adult