Effect of Chronological Age on Pulse Rate Discrimination in Adult Cochlear-Implant Users

Abstract

Cochlear-implant (CI) users rely heavily on temporal envelope cues to understand speech. Temporal processing abilities may decline with advancing age in adult CI users. This study investigated the effect of age on the ability to discriminate changes in pulse rate. Twenty CI users aged 23 to 80 years participated in a rate discrimination task. They attempted to discriminate a 35% rate increase from baseline rates of 100, 200, 300, 400, or 500 pulses per second. The stimuli were electrical pulse trains delivered to a single electrode via direct stimulation to an apical (Electrode 20), a middle (Electrode 12), or a basal location (Electrode 4). Electrically evoked compound action potential amplitude growth functions were recorded at each of those electrodes as an estimate of peripheral neural survival. Results showed that temporal pulse rate discrimination performance declined with advancing age at higher stimulation rates (e.g., 500 pulses per second) when compared with lower rates. The age-related changes in temporal pulse rate discrimination at higher stimulation rates persisted after statistical analysis to account for the estimated peripheral contributions from electrically evoked compound action potential amplitude growth functions. These results indicate the potential contributions of central factors to the limitations in temporal pulse rate discrimination ability associated with aging in CI users.

Neural Adaptation of the Electrically Stimulated Auditory Nerve Is Not Affected by Advanced Age in Postlingually Deafened, Middle-aged, and Elderly Adult Cochlear Implant Users

“…Temporal processing deficits observed in elderly CI users can be attributed to both central (e.g., Moberly et al 2017, 2018; Johnson et al 2021) and peripheral mechanisms. At the peripheral level, results of human temporal bone studies showed that neural damage, including loss of spiral ganglion neurons (SGNs) and peripheral axons of AN fibers, is the major characteristics of age-related hearing loss (Schuknecht & Gacek 1993; Viana et al 2015; Wu et al 2019).…”

“…Specifically, psychophysical measures were conducted using long-duration pulsatile stimulation. In contrast, the AN function was quantified based on either the slope of the eCAP input/output function (Shader et al 2020a(Shader et al , 2020bJohnson et al 2021) or the time constant estimated based on the eCAP HE ET AL. / EAR & HEARING, VOL.…”

“…Specifically, psychophysical measures were conducted using long-duration pulsatile stimulation. In contrast, the AN function was quantified based on either the slope of the eCAP input/output function (Shader et al 2020a, 2020b; Johnson et al 2021) or the time constant estimated based on the eCAP refractory-recovery function (Lee et al 2012). These single-pulse evoked eCAP results do not provide information about the neural representation of long-duration pulsatile stimulation or the effects of prior neural activity on response properties of the AN (e.g., Wilson et al 1997; Matsuoka et al 2000a, 2020b).…”

“…Advanced age has been shown to be negatively associated with speech perception capabilities of CI users, especially in the presence of background noise (Chatelin et al 2004; Vermeire et al 2005; Friedland et al 2010; Budenz et al 2011; Lenarz et al 2012; Dillon et al 2013; Roberts et al 2013; Spitzer et al 2013; Sladen & Zappler 2015; Xie et al 2019). Studies aiming to identify the mechanisms underlying this age-related deficit have primarily focused on auditory processing of temporal cues (e.g., Lee et al 2012; Mussoi & Brown 2019; Xie et al 2019; Shader et al 2020a, 2020b; Johnson et al 2021; Jahn et al 2021) due to their importance for speech perception in CI users (e.g., Fu 2002; Won et al 2011; Winn et al 2012; De Ruiter et al 2015). Results of these studies demonstrated age-related declines in multiple tasks assessing auditory temporal processing.…”

Rate Discrimination Training May Partially Restore Temporal Processing Abilities from Age-Related Deficits

“…Abilities are as good as 3 to 7% for rates of ~ 100 Hz, but performance declines rapidly for rates > 200–300 Hz (e.g., Carlyon and Deeks 2002 ; Carlyon et al 2008 ; Kong et al 2009 ; Macherey and Carlyon 2014 ). The physiological basis for this limitation on rate discrimination may arise from both peripheral and central sources (e.g., Ihlefeld et al 2015 ; Johnson et al 2021 ). Previous studies have demonstrated age-related declines in rate discrimination (DeVries et al 2022 ; Gaskins et al 2019 ) and in other temporal processing tasks, including gap detection (Snell 1997 ), duration discrimination (Fitzgibbons and Gordon‐Salant 1995 ), and tempo discrimination (Fitzgibbons and Gordon-Salant 2001 ).…”