Reaction time sensitivity to spectrotemporal modulations of sound

Abstract

We tested whether joint spectrotemporal sensitivity follows from spectrotemporal separability for normal-hearing conditions and for impaired-hearing simulations. In a manual reaction-time task, normal-hearing listeners had to detect the onset of a ripple (with density between 0-8 cycles/octave and a fixed modulation depth of 50%), that moved up or down the log-frequency axis at constant velocity (between 0-64 Hz), in an otherwise-unmodulated broadband white-noise. Spectral and temporal modulations elicited band-pass filtered sensitivity characteristics, with fastest detection rates around 1 cycle/oct and 32 Hz for normal-hearing conditions. These results closely resemble data from other studies that typically used the modulation-depth threshold as a sensitivity measure for spectral-temporal modulations. To simulate hearing-impairment, stimuli were processed with a 6-channel cochlear-implant vocoder, and a hearing-aid simulation that introduced spectral smearing and low-pass filtering. Reaction times were always much slower compared to normal hearing, especially for the highest spectral densities. Binaural performance was predicted well by the benchmark race model of statistical facilitation of independent monaural channels. For the impaired-hearing simulations this implied a "best-of-both-worlds" principle in which the listeners relied on the hearing-aid ear to detect spectral modulations, and on the cochlear-implant ear for temporal-modulation detection. Although singular-value decomposition indicated that the joint spectrotemporal sensitivity matrix could be largely reconstructed from independent temporal and spectral sensitivity functions, in line with time-spectrum separability, a significant inseparable spectral-temporal interaction was present in all hearing conditions. These results imply that the reaction-time task yields a solid and effective objective measure of acoustic spectrotemporal modulation sensitivity, which may also be applicable to hearing-impaired individuals.

Towards personalized and optimized fitting of cochlear implants

“…The underlying idea is that changing specific parameters in the CI fitting will affect the acoustic processing of the implant and will thus lead to specific changes in the RT distributions (reciprobit lines) for certain ripples, such as illustrated in Figure 4B. In our own experiments, we have so far noted that, typically about 20 trials per ripple suffice to obtain a reliable estimate of the reciprobit line, also for CI users (Veugen, 2017;Veugen et al, 2022). The rationale of the ST ripple test is tentatively illustrated in Figures 6B,C.…”

“…Table 1 proposes a series of auditory performance tests (Pisoni et al, 2017;Veugen, 2017;Wang et al, 2021;Veugen et al, 2022;Noordanus et al, in prep. ) that allow for quantitative and reliable functional assessments of different aspects in the auditory processing chain.…”

“…Auditory reaction times. As an example, Figure 4 demonstrates that also the reaction times of auditory-evoked motor responses follow these strict relationships and that even subtle manipulations of the acoustic input, like reducing the duration of a broadband sound burst from 5 ms to 3 ms Figure 4A) or listening to a modulated sound with either two ears vs. monaurally (Figure 4B; Veugen et al, 2022), systematically and reliably affect the reciprobit lines.…”

“…For example, possible involvement of multiple sub-systems (like bottom-up vs. top-down mechanisms; Carpenter and Williams, 1995), different processing pathways (e.g., frequency channels, ILD, ITD, temporal, spectral, monaural vs. binaural, cortical vs. subcortical, etc. ), uncertainty about the stimulus (the width of the distribution), but also listening effort (cognitive load) can be assessed with reaction time analyses (Carpenter and Williams, 1995;Veugen, 2017;Veugen et al, 2022). Indeed, the latter could serve as a good alternative for the highly noisy and slow pupil-dilation method that is currently measured with video eye-tracker techniques (Zekfeld et al, 2018).…”

“…The ST-ripple RT test. In a reaction-time test with ST-ripples, the ripple is preceded by a period of flat noise of the same carrier and mean sound level as the ripple for a randomized duration, D NOISE (e.g., between [1.0-3.0 s]; Versnel et al, 2009;Massoudi et al, 2014;Veugen, 2017;Veugen et al, 2022;Van der Willigen et al, 2023). The listener must press a button (or touch a keyboard's space bar, handle, or smartphone screen) as soon as the ripple onset is detected.…”