Abstract
Objective: 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.Methods: 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 (FFRENV) and TFS (FFRTFS) components of FFRs were analyzed separately by adding and subtracting the alternative polarity responses, respectively. Speech recognition in noise was evaluated in each participant.Results: 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 FFRENV but not for FFRTFS. Both the H2 and H3 amplitudes and the S-R correlation of FFRENV 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 FFRTFS morphology. Furthermore, the speech-in-noise (SIN) threshold was negatively correlated with the noise-induced change in H2 (for FFRENV) and the S-R correlation for FFRENV in the quiet condition.Conclusion: 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.
Highlights
Presbycusis (PC) is the third most common chronic disorder in elderly people, reflecting the degradation of auditoryprocessing functions in both peripheral and central systems (Yueh et al, 2003)
In another aspect, these results also indicate that frequency following response (FFR) may be a useful objective tool for predicting SIN perception
The main findings are as follows: (1) under quiet conditions, the F0 and H3 amplitudes and the S-R correlation of FFRENV in the PC group were significantly lower than those in the normal hearing (NH) group, but the F1 amplitudes and the S-R correlation of the FFRTFS exhibited no significant differences; (2) under noise conditions, the H2 and H3 amplitudes and S-R correlation of FFRENV in the NH group significantly decreased compared with those under quiet conditions, but no similar alteration was observed in the PC group or for FFRTFS; (3) the higher degree of hearing loss was correlated with greater changes in temporal fine structure (TFS) morphology caused by noise; and (4) better SIN performance was closely related to higher FFRENV S-R correlation in the quiet condition and higher H2 (FFRENV) amplitude alteration in the noise condition. 0.091 (0.765)
Summary
Presbycusis (PC) is the third most common chronic disorder in elderly people, reflecting the degradation of auditoryprocessing functions in both peripheral and central systems (Yueh et al, 2003). Listeners with PC often manifest both symmetrical sensorineural hearing loss (SNHL) and impaired speech recognition (Deng et al, 2014), especially in noisy environments (Li et al, 2004; Divenyi et al, 2005; Gifford et al, 2007; Huang et al, 2008; Salonen et al, 2013). After a soundwave (such as speech sound) reaches the ears, the peripheral auditory system filters the sound wave into bands of narrowband waves through a series of band-pass filters, and the output signals from each of the narrowband channels are further decomposed into fast fluctuating temporal fine structures (TFSs) and slowly varying envelopes (ENVs; Moore, 2008). It is of interest and importance to determine whether the age-related deficits in processing TFS and envelope signals start to occur at the level of the auditory brainstem
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
