Training spatial hearing in unilateral cochlear implant users through reaching to sounds in virtual reality

Abstract

Background and purpose: Use of unilateral cochlear implant (UCI) is associated with limited spatial hearing skills. Evidence that training these abilities in UCI user is possible remains limited. In this study, we assessed whether a Spatial training based on hand-reaching to sounds performed in virtual reality improves spatial hearing abilities in UCI users METHODS: Using a crossover randomized clinical trial, we compared the effects of a Spatial training protocol with those of a Non-Spatial control training. We tested 17 UCI users in a head-pointing to sound task and in an audio-visual attention orienting task, before and after each training. <br>Study is recorded in clinicaltrials.gov (NCT04183348).

Results: During the Spatial VR training, sound localization errors in azimuth decreased. Moreover, when comparing head-pointing to sounds before vs. after training, localization errors decreased after the Spatial more than the control training. No training effects emerged in the audio-visual attention orienting task.

Conclusions: Our results showed that sound localization in UCI users improves during a Spatial training, with benefits that extend also to a non-trained sound localization task (generalization). These findings have potentials for novel rehabilitation procedures in clinical contexts.

Keywords: Active listening; Cochlear implant; Head movements; Reaching; Spatial hearing; VR training; Virtual reality.

Fig. 1

Experimental procedure and setting. A Schematic description of the overall crossover design. Each session (Session 1 and Session 2) comprised two testing phases, separated by a training task: Non-Spatial VR in blue and Spatial VR in green. B Testing phases. Left: schematic representation of the participant wearing the HMD and holding the VR controller during the head-pointing sound localization task. The grey circles represent the 8 possible positions in which the real loudspeaker could be placed (shown here only for illustration purposes, as no visual cue to sound position was available in the VR environment). They were located 55 cm from the center of the subject’s head, at different azimuth (± 22.5° and ± 67.5° with respect to the midsagittal plane) and vertical positions (5° and − 15° with respect to the plane passing through the ears). Note that the real speaker was never visible in the VR environment. Right: schematic representation of the setting for the audio-visual cueing task (conducted entirely outside VR). C Training phase. Left: close-up of the scene as visible inside the HMD from participant’s perspective. The virtual scenario comprised a room, 13 speakers and the VR controller held in participants’ hands. Right: schematic representation of the participant wearing the HMD and holding the VR controller during the training tasks

Fig. 2

Sound localization performance. A Absolute error along azimuth, as a function of trial in the Spatial training. Linear regression (solid line) with 95% confidence intervals (dashed lines). To the left, slope for each participant extracted from the LME model used in the analysis. B Absolute localization across the four testing sessions of the experimental design, separately for participants who completed the Spatial training on session 1 (grey) or session 2 (black line). Error bars represent standard errors. C Absolute localization error along azimuth dimension as a function of training (Spatial: right and Non-Spatial: left), phase (Pre: grey and Post: black) and hearing threshold in the contralateral ear (x axis). D Onset of the first head movements in seconds as a function of phase (pre-training in black and post-training in grey) and trainings. Error bars represent standard errors. In A and C, circles represent participants who wore hearing aid in the contralateral ear (N = 10) and triangles who did not have hearing aid (N = 7)

Fig. 3

Head rotation during the Spatial training. A Number of head movements across trial repetition as a function of sound eccentricity (central positions in grey and peripherical positions in black). B Extent of head rotation across trial repetition as a function of sound eccentricity (central positions in grey and peripherical positions in black)

Fig. 4

Head-rotation bias during the Head-pointing to sounds task, as a function of training (Spatial Training and Non-Spatial training) and Phase (Before training in black and post-training in grey). Error bars represent standard errors