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

The Efficacy of Wireless Auditory Training in Unilateral Hearing Loss Rehabilitation

PURPOSE

The purpose of this study was to evaluate the efficacy of auditory training (AT) in patients with unilateral hearing loss (UHL) using hearing aids (HAs), comparing traditional methods with a new approach involving a wireless remote microphone.

METHODS

The study included 96 participants, divided into two groups, with ages ranging from 42 to 64 years, comprising both male and female subjects. A clinical trial including consecutive moderate UHL patients was performed at our institution. For the study group, a Roger Pen was used during AT with patients inside a sound-attenuating cabin. Controls followed conventional sessions. Professional speech and language pathologists performed the rehabilitation. Audiological outcomes were measured, including word recognition at signal-to-noise ratios (SNRs) of 0 dB, +5 dB, and +10 dB, to determine the effectiveness of the training. Measurements also included the Speech, Spatial, and Qualities of Hearing Scale to assess perceived auditory abilities.

RESULTS

A total of 46 and 50 UHL patients were randomly included in the study and control groups, respectively. No differences were found in terms of sex, age, presence of tinnitus, duration of hearing loss, pure tone average, and speech-in-noise perception without an HA. Following HA fitting and AT, a notable enhancement in the ability to identify speech in noisy environments was observed in the study group. This improvement was significant at SNRs of +5 and +10. When comparing the ability to identify speech in noise using HAs across both groups, it was observed that hearing capabilities post-wireless AT showed a significant improvement at an SNR of +5. Only the study group had a significant improvement in the total Speech, Spatial, and Qualities of Hearing Scale score after the training.

CONCLUSIONS

In our group of UHL patients, we found significantly better speech-in-noise perception when HA fitting was followed by wireless AT. Wireless AT may facilitate usage of HAs, leading to binaural hearing in UHL patients. Our findings suggest that future interventions might benefit from incorporating wireless technology in AT programs.

Motor Strategies: The Role of Active Behavior in Spatial Hearing Research

When completing a task, the ability to implement behavioral strategies to solve it in an effective and cognitively less-demanding way is extremely adaptive for humans. This behavior makes it possible to accumulate evidence and test one's own predictions about the external world. In this work, starting from examples in the field of spatial hearing research, I analyze the importance of considering motor strategies in perceptual tasks, and I stress the urgent need to create ecological experimental settings, which are essential in allowing the implementation of such behaviors and in measuring them. In particular, I will consider head movements as an example of strategic behavior implemented to solve acoustic space-perception tasks.

Spatial hearing training in virtual reality with simulated asymmetric hearing loss

Sound localization is essential to perceive the surrounding world and to interact with objects. This ability can be learned across time, and multisensory and motor cues play a crucial role in the learning process. A recent study demonstrated that when training localization skills, reaching to the sound source to determine its position reduced localization errors faster and to a greater extent as compared to just naming sources' positions, despite the fact that in both tasks, participants received the same feedback about the correct position of sound sources in case of wrong response. However, it remains to establish which features have made reaching to sound more effective as compared to naming. In the present study, we introduced a further condition in which the hand is the effector providing the response, but without it reaching toward the space occupied by the target source: the pointing condition. We tested three groups of participants (naming, pointing, and reaching groups) each while performing a sound localization task in normal and altered listening situations (i.e. mild-moderate unilateral hearing loss) simulated through auditory virtual reality technology. The experiment comprised four blocks: during the first and the last block, participants were tested in normal listening condition, while during the second and the third in altered listening condition. We measured their performance, their subjective judgments (e.g. effort), and their head-related behavior (through kinematic tracking). First, people's performance decreased when exposed to asymmetrical mild-moderate hearing impairment, more specifically on the ipsilateral side and for the pointing group. Second, we documented that all groups decreased their localization errors across altered listening blocks, but the extent of this reduction was higher for reaching and pointing as compared to the naming group. Crucially, the reaching group leads to a greater error reduction for the side where the listening alteration was applied. Furthermore, we documented that, across blocks, reaching and pointing groups increased the implementation of head motor behavior during the task (i.e., they increased approaching head movements toward the space of the sound) more than naming. Third, while performance in the unaltered blocks (first and last) was comparable, only the reaching group continued to exhibit a head behavior similar to those developed during the altered blocks (second and third), corroborating the previous observed relationship between the reaching to sounds task and head movements. In conclusion, this study further demonstrated the effectiveness of reaching to sounds as compared to pointing and naming in the learning processes. This effect could be related both to the process of implementing goal-directed motor actions and to the role of reaching actions in fostering the implementation of head-related motor strategies.

Free-Field Hearing Test in Noise with Free Head Rotation for Evaluation of Monaural Hearing

There is a discrepancy between the hearing test results in patients with single-sided deafness (SSD) and their reported outcome measures. This is probably due to the presence of two elements in everyday situations: noise and head movements. We developed a stereo-audiometric test in noise with free head movements to evaluate movements and auditory performance in monaural and binaural conditions in normal hearing volunteers with one occluded ear. Tests were performed in the binaural condition (BIN), with the left ear (LEO) or the right ear occluded (REO). The signal was emitted by one of the seven speakers, placed every 30° in a semicircle, and the noise (cocktail party) by all speakers. Subjects turned their head freely to obtain the most comfortable listening position, then repeated 10 sentences in this position. In monaural conditions, the sums of rotations (head rotations for an optimal hearing position in degrees, random signal azimuth, 1 to 15 signal ad lib signal presentations) were higher (LEO 255 ± 212°, REO 308 ± 208° versus BIN 74 ± 76, p < 0.001, ANOVA) than those in the BIN condition and the discrimination score (out of 10) was lower than that in the BIN condition (LEO 5 ± 1, REO 7 ± 1 versus BIN 8 ± 1, respectively p < 0.001 and p < 0.05 ANOVA). In the monaural condition, total rotation and discrimination in noise were negatively correlated with difficulty (Pearson r = -0.68, p < 0.01 and -0.51, p < 0.05, respectively). Subjects' behaviors were different in optimizing their hearing in noise via head rotation. The evaluation of head movements seems to be a significant parameter in predicting the difficulty of monaural hearing in noisy environments.

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.