Dichotic listening performance with cochlear-implant simulations of ear asymmetry is consistent with difficulty ignoring clearer speech

Abstract

There are an increasing number of bilateral and single-sided-deafness cochlear-implant (CI) users who hope to achieve improved spatial-hearing abilities through access to sound in both ears. It is, however, unclear how speech is processed when inputs are functionally asymmetrical, which may have an impact on spatial-hearing abilities. Therefore, functionally asymmetrical hearing was controlled and parametrically manipulated using a channel vocoder as a CI simulation. In Experiment 1, normal-hearing (NH) listeners performed a dichotic listening task (i.e., selective attention to one ear, ignoring the other) using asymmetrical signal degradation. Spectral resolution varied independently in each ear (4, 8, 16 channels, and unprocessed control). Performance decreased with decreasing resolution in the target ear and increasing resolution in the interferer ear. In Experiment 2, these results were replicated using a divided attention task (attend to both ears, report one after sentence completion) in both NH and bilateral CI listeners, although overall performance was lower than in Experiment 1. In Experiment 3, frequency-to-place mismatch simulated shallow CI insertion depths (0, 3, 6-mm shifts, and unprocessed control). Performance mostly decreased with increasing shift in the target ear and decreasing shift in the interferer ear; however, performance nonmonotonicities occurred. The worst performance occurred when the shift matched across ears, suggesting that pitch similarity increases difficulty. The results show that it is more difficult to attend an ear that is relatively degraded or distorted, which may set spatial-hearing limitations for CI users when trying to attend to a target in complex auditory scenes.

Interaural asymmetry of dynamic range: Abnormal fusion, bilateral interference, and shifts in attention

“…The first supposes that it results from a failure of sound source segregation cues to form distinct auditory objects ( Gallun et al, 2007 ; Reiss et al, 2016 ; Reiss and Molis, 2021 ). The second supposes that contralateral interference results from a failure to allocate attention away from the source with greatest spectro-temporal fidelity and toward a more degraded sound source ( Goupell et al, 2016 , 2021 ).…”

“…An attentional basis of contralateral interference is suggested by the finding that performance remains intact if the target is in the better ear. This has been demonstrated for listeners with BiCIs (Goupell et al, 2016(Goupell et al, , 2018Bakal et al, 2021), listeners with one CI and one NH ear (Bernstein et al, 2016(Bernstein et al, , 2020, and simulations of BiCIs in listeners with NH (Goupell et al, 2021). If contralateral interference results purely from an inability to segregate target from masker, then it should not matter whether the target is in the better or poorer ear.…”

“…Listeners with a CI in one ear and NH in the other ear show the same pattern of 10.3389/fnins.2022.1018190 performance (Bernstein et al, 2020). In simulations of BiCIs, contralateral interference occurs when one or both ears have poor spectro-temporal resolution (Gallun et al, 2007;Goupell et al, 2021). Two mechanisms have been proposed to drive contralateral interference in experiments where the target is presented to one ear and the masker is presented to one or both ears.…”

“…This disruptive fusion could therefore occur within the ear containing the target, across ears, or both. The second is a failure of attention, where it is more difficult to ignore the clearer stimulus ( Goupell et al, 2021 ).…”

Development of Ultrasensitive Biomimetic Auditory Hair Cells Based on Piezoresistive Hydrogel Nanocomposites

“…These devices have created an excellent translational therapy to enable thousands of hearing-impaired individuals to gain some level of hearing ability. However, there are several limitations with the current cochlear implant devices, which limit their functionality, such as difficulty in stimulating the cochlear nerve at low frequencies and limited pitch perception . Engineering hair cells could potentially lead to developing a new generation of cochlear implant devices to overcome these issues, with several additional benefits such as much improved frequency discrimination.…”