AUTHOR=Hao Wenyang , Wang Qian , Li Liang , Qiao Yufei , Gao Zhiqiang , Ni Daofeng , Shang Yingying 

TITLE=Effects of Phase-Locking Deficits on Speech Recognition in Older Adults With Presbycusis

JOURNAL=Frontiers in Aging Neuroscience

VOLUME=10

YEAR=2018

URL=https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2018.00397

DOI=10.3389/fnagi.2018.00397

ISSN=1663-4365

ABSTRACT=<p><bold>Objective</bold>: People with presbycusis (PC) often report difficulties in speech recognition, especially under noisy listening conditions. Investigating the PC-related changes in central representations of envelope signals and temporal fine structure (TFS) signals of speech sounds is critical for understanding the mechanism underlying the PC-related deficit in speech recognition. Frequency-following responses (FFRs) to speech stimulation can be used to examine the subcortical encoding of both envelope and TFS speech signals. This study compared FFRs to speech signals between listeners with PC and those with clinically normal hearing (NH) under either quiet or noise-masking conditions.</p><p><bold>Methods</bold>: FFRs to a 170-ms speech syllable /da/ were recorded under either a quiet or noise-masking (with a signal-to-noise ratio (SNR) of 8 dB) condition in 14 older adults with PC and 13 age-matched adults with NH. The envelope (FFR<sub>ENV</sub>) and TFS (FFR<sub>TFS</sub>) components of FFRs were analyzed separately by adding and subtracting the alternative polarity responses, respectively. Speech recognition in noise was evaluated in each participant.</p><p><bold>Results</bold>: In the quiet condition, compared with the NH group, the PC group exhibited smaller F0 and H3 amplitudes and decreased stimulus-response (S-R) correlation for FFR<sub>ENV</sub> but not for FFR<sub>TFS</sub>. Both the H2 and H3 amplitudes and the S-R correlation of FFR<sub>ENV</sub> significantly decreased in the noise condition compared with the quiet condition in the NH group but not in the PC group. Moreover, the degree of hearing loss was correlated with noise-induced changes in FFR<sub>TFS</sub> morphology. Furthermore, the speech-in-noise (SIN) threshold was negatively correlated with the noise-induced change in H2 (for FFR<sub>ENV</sub>) and the S-R correlation for FFR<sub>ENV</sub> in the quiet condition.</p><p><bold>Conclusion</bold>: Audibility affects the subcortical encoding of both envelope and TFS in PC patients. The impaired ability to adjust the balance between the envelope and TFS in the noise condition may be part of the mechanism underlying PC-related deficits in speech recognition in noise. FFRs can predict SIN perception performance.</p>