Objective evidence of temporal processing deficits in older adults

Abstract

The older listener's ability to understand speech in challenging environments may be affected by impaired temporal processing. This review summarizes objective evidence of degraded temporal processing from studies that have used the auditory brainstem response, auditory steady-state response, the envelope- or frequency-following response, cortical auditory-evoked potentials, and neural tracking of continuous speech. Studies have revealed delayed latencies and reduced amplitudes/phase locking in subcortical responses in older vs. younger listeners, in contrast to enhanced amplitudes of cortical responses in older listeners. Reconstruction accuracy of responses to continuous speech (e.g., cortical envelope tracking) shows over-representation in older listeners. Hearing loss is a factor in many of these studies, even though the listeners would be considered to have clinically normal hearing thresholds. Overall, the ability to draw definitive conclusions regarding these studies is limited by the use of multiple stimulus conditions, small sample sizes, and lack of replication. Nevertheless, these objective measures suggest a need to incorporate new clinical measures to provide a more comprehensive assessment of the listener's speech understanding ability, but more work is needed to determine the most efficacious measure for clinical use.

Keywords: Aging; Auditory brainstem response; Auditory steady-state response; Cortical auditory-evoked potential; Envelope tracking; Frequency-following response; Hearing impairment; Magnetoencephalography; Temporal processing.

Fig. 1.

Individual audiograms (top panel) and auditory brainstem response waveforms (bottom panel) are displayed for representative young normal-hearing (YNH, blue squares), older normal-hearing (ONH, red triangles), and older hearing-impaired (OHI, black circles) listeners. Even slight high-frequency loss above 4000 Hz is associated with Wave V latency delays.

Fig. 2.

Spectral energy corresponding to pulse-train presentation rates shows that responses in younger normal-hearing listeners (YNH, top panel) have higher frequency energy than in older normal-hearing listeners (ONH, bottom panel) that is significant for the 400-Hz rate. Furthermore, a decrease in spectral energy with higher rates is only significant in the ONH listeners. Used with permission from Gaskins et al. (2019).

Fig. 3.

FFR spectral amplitudes to dynamic frequency changes are displayed for a representative young normal-hearing listener (left panel) and a representative older normal-hearing listener (right panel). The responses in the younger listener show more robust tracking of dynamic frequency than the responses of the older listener across rates of change. Used with permission from Clinard et al. (2015).

Fig. 4.

An abrupt loss of synchrony in the later response regions to the vowel [a] is noted in older normal-hearing (ONH) listeners’ responses in panels A and B. This drop was not seen in the younger normal-hearing (YNH) listeners. The dashed pink rectangle delineates this later region where a dramatic decrease in response amplitude (A) and frequency energy (B) can be seen in the ONH responses. Modified with permission from Presacco et al. (2015).

Fig. 5.

Stimulus-to-response correlation ‘r’ values are lower in ONH than in YNH listeners for the word WEED but not for WHEAT. Panel A shows stimulus waveforms that differ only in vowel duration. Panel B shows response waveforms in young normal-hearing (YNH, blue) and older normal-hearing (ONH, red) listeners. A drop in neural synchrony is apparent in the ONH listeners at approximately 185 ms. Panel C displays individual (open symbols) and mean (closed symbols) for YNH (blue circles) and ONH (red triangles) listeners. Error bars: ± 1 standard error. ***p < 0.001. Modified with permission from Roque et al. (2019a).

Fig. 6.

Left panel: Group average waveforms show that increasing voice-onset-time (VOT) results in increased latencies of P1, N1, and P2 peaks of the cortical auditory-evoked response. Right panels: N1 and P2 peaks show greater delays with increasing VOTs in older normal-hearing (ONH, filled circles) and older hearing-impaired (OHI, open triangles) listeners compared to young normal-hearing (YNH, open circles) listeners. Error bars: 1 standard error. Used with permission from Tremblay et al. (2003).

Fig. 7.

Panel A: Older listeners’ cortical responses (ONH; black squares) show higher reconstruction accuracies (r values) in quiet and across SNR conditions compared to younger responses (YNH; red circles). Responses of both groups are above the noise floor (blue line). Panel B: ONH responses show a reduction in reconstruction accuracy as the integration time window is narrowed from 500 ms to 150 ms in both quiet and noise conditions, but the YNH responses do not show a similar decrease in reconstruction accuracy. Error bars: ± 1 standard error. *p < 0.05, **p < 0.01, ***p < 0.001, N.S. = not significant. Modified with permission from Presacco et al. (2016a).