Intensive Training of Spatial Hearing Promotes Auditory Abilities of Bilateral Cochlear Implant Adults: A Pilot Study

Abstract

Objective: The aim of this study was to evaluate the feasibility of a virtual reality-based spatial hearing training protocol in bilateral cochlear implant (CI) users and to provide pilot data on the impact of this training on different qualities of hearing. Design: Twelve bilateral CI adults aged between 19 and 69 followed an intensive 10-week rehabilitation program comprised eight virtual reality training sessions (two per week) interspersed with several evaluation sessions (2 weeks before training started, after four and eight training sessions, and 1 month after the end of training). During each 45-minute training session, participants localized a sound source whose position varied in azimuth and/or in elevation. At the start of each trial, CI users received no information about sound location, but after each response, feedback was given to enable error correction. Participants were divided into two groups: a multisensory feedback group (audiovisual spatial cue) and an unisensory group (visual spatial cue) who only received feedback in a wholly intact sensory modality. Training benefits were measured at each evaluation point using three tests: 3D sound localization in virtual reality, the French Matrix test, and the Speech, Spatial and other Qualities of Hearing questionnaire. Results: The training was well accepted and all participants attended the whole rehabilitation program. Four training sessions spread across 2 weeks were insufficient to induce significant performance changes, whereas performance on all three tests improved after eight training sessions. Front-back confusions decreased from 32% to 14.1% (p = 0.017); speech recognition threshold score from 1.5 dB to −0.7 dB signal-to-noise ratio (p = 0.029) and eight CI users successfully achieved a negative signal-to-noise ratio. One month after the end of structured training, these performance improvements were still present, and quality of life was significantly improved for both self-reports of sound localization (from 5.3 to 6.7, p = 0.015) and speech understanding (from 5.2 to 5.9, p = 0.048). Conclusions: This pilot study shows the feasibility and potential clinical relevance of this type of intervention involving a sensorial immersive environment and could pave the way for more systematic rehabilitation programs after cochlear implantation.

Audiovisual Training in Virtual Reality Improves Auditory Spatial Adaptation in Unilateral Hearing Loss Patients

“…This effect of multisensory training on unisensory experience was also found in adult patients with bilateral cochlear implants (BCIs); a study by [ 22 ] showed faster improvement after multisensory spatial training compared to training in the auditory modality only. Although both populations (UHL and BCIs) have different adaptation strategies, they both rely on visual sensory inputs to optimize environmental spatial mapping [ 25 ].…”

“…Anatomically, this can be explained by the presence of direct projections originating from the representation of the peripheral visual fields in the pre-striate cortex [ 20 ] towards the caudal areas of the auditory cortex, which are involved in spatial processing [ 21 ]. A large body of studies proved that multisensory stimulation that includes visual feedback is more effective than unisensory stimulation in normal-hearing participants with monaural plugs [ 15 , 16 , 18 , 22 ] and in patients with cochlear implants [ 17 , 23 ]. The study of [ 15 ] suggests that unisensory auditory training, applied to normal-hearing participants with ear plugs, showed no improvement in spatial behavior.…”

“…The spontaneous reaction of turning the head and body towards a sound source has been found to be an important factor in weighing auditory cues [ 27 , 28 ]. Studies comparing static and active listening conditions showed better spatial performance when head movements were allowed [ 18 , 22 , 29 ].…”

“…In the study of [ 15 ] on monaurally plugged normal hearing controls the number of sessions of spatial audiovisual training was five training sessions during one week (one session per day). A recent study by Coudert et al [ 22 ] on bilateral cochlear implants showed that intensive spatial training of eight sessions over 10 weeks significantly improved spatial performance and also performance in the speech in noise, which was evaluated by a matrix test, while four sessions spread over 2 weeks seemed to be insufficient. Such results indicate that the number of sessions and the duration between each session are important factors for the efficiency of a training program.…”

Active sound source localization in bilateral hearing-impaired children

“…Multimodal training protocols have been developed 17 to enhance the spatial hearing abilities of CI users. While attending these protocols, patients are encouraged to actively explore the environment, as movements enrich the incoming auditory information about space.…”