Capturing Visual Attention With Perturbed Auditory Spatial Cues.

Lateralized sounds can orient visual attention, with benefits for audio-visual processing. Here, we asked to what extent perturbed auditory spatial cues-resulting from cochlear implants (CI) or unilateral hearing loss (uHL)-allow this automatic mechanism of information selection from the audio-visual environment. We used a classic paradigm from experimental psychology (capture of visual attention with sounds) to probe the integrity of audio-visual attentional orienting in 60 adults with hearing loss: bilateral CI users (N = 20), unilateral CI users (N = 20), and individuals with uHL (N = 20). For comparison, we also included a group of normal-hearing (NH, N = 20) participants, tested in binaural and monaural listening conditions (i.e., with one ear plugged). All participants also completed a sound localization task to assess spatial hearing skills. Comparable audio-visual orienting was observed in bilateral CI, uHL, and binaural NH participants. By contrast, audio-visual orienting was, on average, absent in unilateral CI users and reduced in NH listening with one ear plugged. Spatial hearing skills were better in bilateral CI, uHL, and binaural NH participants than in unilateral CI users and monaurally plugged NH listeners. In unilateral CI users, spatial hearing skills correlated with audio-visual-orienting abilities. These novel results show that audio-visual-attention orienting can be preserved in bilateral CI users and in uHL patients to a greater extent than unilateral CI users. This highlights the importance of assessing the impact of hearing loss beyond auditory difficulties alone: to capture to what extent it may enable or impede typical interactions with the multisensory environment.

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

Unilateral hearing loss (UHL) leads to an alteration of binaural cues resulting in a significant increment of spatial errors in the horizontal plane. In this study, nineteen patients with UHL were recruited and randomized in a cross-over design into two groups; a first group (n = 9) that received spatial audiovisual training in the first session and a non-spatial audiovisual training in the second session (2 to 4 weeks after the first session). A second group (n = 10) received the same training in the opposite order (non-spatial and then spatial). A sound localization test using head-pointing (LOCATEST) was completed prior to and following each training session. The results showed a significant decrease in head-pointing localization errors after spatial training for group 1 (24.85° ± 15.8° vs. 16.17° ± 11.28°; p < 0.001). The number of head movements during the spatial training for the 19 participants did not change (p = 0.79); nonetheless, the hand-pointing errors and reaction times significantly decreased at the end of the spatial training (p < 0.001). This study suggests that audiovisual spatial training can improve and induce spatial adaptation to a monaural deficit through the optimization of effective head movements. Virtual reality systems are relevant tools that can be used in clinics to develop training programs for patients with hearing impairments.

Brain plasticity and auditory spatial adaptation in patients with unilateral hearing loss.

The ability to localize sounds in patients with Unilateral Hearing Loss (UHL) is usually disrupted due to alteration in the integration of binaural cues. Nonetheless, some patients are able to compensate deficit using adaptive strategies. In this study, we explored the neural correlates underlying this adaptation. Twenty-one patients with UHL were separated into 3 groups using cluster analysis based on their binaural performance. The resulting clusters were referred to as better, moderate, and poorer performers cluster (BPC, MPC, and PPC). We measured the mismatch negativity (MMN) elicited by deviant sounds located at 10°, 20°, and 100° from a standard positioned at 50° ipsilateral to the deaf ear. The BPC exhibited significant MMN for all 3 deviants, similar to normal hearing (NH) subjects. In contrast, there was no significant MMN for 10° and 20° deviants for the PPC and for NH when one ear was plugged and muffed. Scalp distribution was maximal over central regions in BPC, while PPC showed more frontal MMN distribution. Thus, the BPC exhibited a contralateral activation pattern, similar to NH, while the PPC exhibited more symmetrical hemispheric activation. MMN can be used as a neural marker to reflect spatial adaptation in patients with UHL.