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We assessed if spatial hearing training improves sound localization in bilateral cochlear implant (BCI) users and whether its benefits can generalize to untrained sound localization tasks.In 20 BCI users, we assessed the effects of two training procedures (spatial versus nonspatial control training) on two different tasks performed before and after training (head-pointing to sound and audiovisual attention orienting). In the spatial training, participants identified sound position by reaching toward the sound sources with their hand. In the nonspatial training, comparable reaching movements served to identify sound amplitude modulations. A crossover randomized design allowed comparison of training procedures within the same participants. Spontaneous head movements while listening to the sounds were allowed and tracked to correlate them with localization performance.During spatial training, BCI users reduced their sound localization errors in azimuth and adapted their spontaneous head movements as a function of sound eccentricity. These effects generalized to the head-pointing sound localization task, as revealed by greater reduction of sound localization error in azimuth and more accurate first head-orienting response, as compared to the control nonspatial training. BCI users benefited from auditory spatial cues for orienting visual attention, but the spatial training did not enhance this multisensory attention ability.Sound localization in BCI users improves with spatial reaching-to-sound training, with benefits to a nontrained sound localization task. These findings pave the way to novel rehabilitation procedures in clinical contexts.

Localising sounds means having the ability to process auditory cues deriving from the interplay among sound waves, the head and the ears. When auditory cues change because of temporary or permanent hearing loss, sound localization becomes difficult and uncertain. The brain can adapt to altered auditory cues throughout life and multisensory training can promote the relearning of spatial hearing skills. Here, we study the training potentials of sound-oriented motor behaviour to test if a training based on manual actions toward sounds can learning effects that generalize to different auditory spatial tasks. We assessed spatial hearing relearning in normal hearing adults with a plugged ear by using visual virtual reality and body motion tracking. Participants performed two auditory tasks that entail explicit and implicit processing of sound position (head-pointing sound localization and audio-visual attention cueing, respectively), before and after having received a spatial training session in which they identified sound position by reaching to auditory sources nearby. Using a crossover design, the effects of the above-mentioned spatial training were compared to a control condition involving the same physical stimuli, but different task demands (i.e., a non-spatial discrimination of amplitude modulations in the sound). According to our findings, spatial hearing in one-ear plugged participants improved more after reaching to sound trainings rather than in the control condition. Training by reaching also modified head-movement behaviour during listening. Crucially, the improvements observed during training generalize also to a different sound localization task, possibly as a consequence of acquired and novel head-movement strategies.

When localising sounds in space the brain relies on internal models that specify the correspondence between the auditory input reaching the ears and initial head-position with coordinates in external space. These models can be updated throughout life, setting the basis for re-learning spatial hearing abilities in adulthood. This is particularly important for individuals who experience long-term auditory alterations (e.g., hearing loss, hearing aids, cochlear implants) as well as individuals who have to adapt to novel auditory cues when listening in virtual auditory environments. Until now, several methodological constraints have limited our understanding of the mechanisms involved in spatial hearing re-learning. In particular, the potential role of active listening and head-movements have remained largely overlooked. Here, we overcome these limitations by using a novel methodology, based on virtual reality and real-time kinematic tracking, to study the role of active multisensory-motor interactions with sounds in the updating of sound-space correspondences. Participants were immersed in a virtual reality scenario showing 17 speakers at ear-level. From each visible speaker a free-field real sound could be generated. Two separate groups of participants localised the sound source either by reaching or naming the perceived sound source, under binaural or monaural listening. Participants were free to move their head during the task and received audio-visual feedback on their performance. Results showed that both groups compensated rapidly for the short-term auditory alteration caused by monaural listening, improving sound localisation performance across trials. Crucially, compared to naming, reaching the sounds induced faster and larger sound localisation improvements. Furthermore, more accurate sound localisation was accompanied by progressively wider head-movements. These two measures were significantly correlated selectively for the Reaching group. In conclusion, reaching to sounds in an immersive visual VR context proved most effective for updating altered spatial hearing. Head movements played an important role in this fast updating, pointing to the importance of active listening when implementing training protocols for improving spatial hearing.HIGHLIGHTS- We studied spatial hearing re-learning using virtual reality and kinematic tracking- Audio-visual feedback combined with active listening improved monaural sound localisation- Reaching to sounds improved performance more than naming sounds- Monaural listening triggered compensatory head-movement behaviour- Head-movement behaviour correlated with re-learning only when reaching to sounds

Nowadays behavioral and cognitive neuroscience studies have turned ‘naturalistic’, aiming at understanding brain functions by maintaining complexity close to everyday life. Many scholars started using commercially available VR devices, which, were not conceived as research tools. It is therefore important to assess their spatio-temporal reliability and inform scholars about the basic resolutions they can achieve. Here we provide such an assessment for the VIVE (HTC Vive) by comparing it with a VICON (BONITA 10) system. Results show a submillimeter Vive precision (0.237mm) and a nearest centimeter accuracy (8.7mm static, 8.5mm dynamic). we also report the Vive reaction to a tracking loss: the system takes 319.5 +/− 16.8 ms to detect the loss and can still be perturbed for about 3 seconds after tracking recovery. The Vive device allows for fairly accurate and reliable spatiotemporal measurements and may be well-suited for studies with typical human behavior, provided tracking loss is prevented.

Previous research using immersive virtual reality (VR) has shown that after a short period of embodiment by White people in a Black virtual body, their implicit racial bias against Black people diminishes. Here we tested the effects of some socio-cognitive variables that could contribute to enhancing or reducing the implicit racial bias. The first aim of the study was to assess the beneficial effects of cooperation within a VR scenario, the second aim was to provide preliminary testing of the hypothesis that empathy and political attitudes could contribute to implicit bias about race, while the third aim was to explore the relationship between political attitudes and empathy. We had (Caucasian) participants embodied in a Black virtual body and engaged either in a cooperative (Coop group) or in a non-cooperative (Neutral group) activity with a confederate experimenter embodying another Black avatar. Before and after VR, we measured participants’ implicit racial bias by means of Implicit Association Test (IAT) and their perceived closeness toward the confederate experimenter. Before VR we also assessed participants’ political attitudes and empathy traits. Results revealed that, as compared to the Neutral group, the Coop group showed lower IAT scores after the social interaction. Interestingly, in the Neutral but not the Coop group the perceived closeness toward the confederate experimenter was associated with the initial racial bias: the more the participants reduced their distance, the more they reduced their IAT score. Moreover, reported traits of empathy and political attitudes significantly explained the variance observed in the initial implicit bias, with perspective-taking, empathic concern, and personal distress being significant predictors of the IAT scores. Finally, there was a relationship between political attitudes and empathy: the more participants considered themselves as left-wing voters, the higher their perspective-taking and empathic concern scores. We discuss these findings within the neuroscientific and social cognition field and encourage scholars from different domains to further explore whether and under which conditions a given manipulation for reducing racial bias could be efficiently transposed in VR.