Virtually spatialized sounds enhance auditory processing in healthy participants and patients with a disorder of consciousness

Lizette Heine,Alexandra Corneyllie,Fabien Perrin,Jacques Luauté,Mathieu Lavandier,Florent Gobert

doi:10.1038/s41598-021-93151-6

Abstract

Neuroscientific and clinical studies on auditory perception often use headphones to limit sound interference. In these conditions, sounds are perceived as internalized because they lack the sound-attributes that normally occur with a sound produced from a point in space around the listener. Without the spatial attention mechanisms that occur with localized sounds, auditory functional assessments could thus be underestimated. We hypothesize that adding virtually externalization and localization cues to sounds through headphones enhance sound discrimination in both healthy participants and patients with a disorder of consciousness (DOC). Hd-EEG was analyzed in 14 healthy participants and 18 patients while they listened to self-relevant and irrelevant stimuli in two forms: diotic (classic sound presentation with an “internalized” feeling) and convolved with a binaural room impulse response (to create an “externalized” feeling). Convolution enhanced the brains’ discriminative response as well as the processing of irrelevant sounds itself, in both healthy participants and DOC patients. For the healthy participants, these effects could be associated with enhanced activation of both the dorsal (where/how) and ventral (what) auditory streams, suggesting that spatial attributes support speech discrimination. Thus, virtually spatialized sounds might “call attention to the outside world” and improve the sensitivity of assessment of brain function in DOC patients.

Highlights

Neuroscientific and clinical studies on auditory perception often use headphones to limit sound interference
A significantly stronger externalization percept can be obtained by convolving the sound with a binaural room impulse response (BRIR) that is a head related transfer function (HRTF) recorded in a r oom[15,16]
We assessed the effect of realistic spatialized sounds on speech discrimination, as compared to diotic sounds in both healthy conscious participants and patients with a disorder of consciousness (DOC)

Summary

Introduction

Neuroscientific and clinical studies on auditory perception often use headphones to limit sound interference. Sound localization is possible due to slight binaural differences in time and level, as well as reverberation within the space surrounding the subject Contrary to these normal listening situations, neuroscientific and clinical studies almost exclusively use diotic sounds (identical signals in both ears) and headphones to investigate auditory perception. Convolving the sound with a head related transfer function (HRTF), taking into account sound filtering by the head and pinnae (in an anechoic room), gives the impression of a sound-source outside the head[12] The presentation of these “externalized” sounds is associated with enhanced activations of the auditory “where/how” pathway, among others in the posterior superior temporal gyrus and inferior parietal lobule[13]. The effects of such realistic spatialized sounds (i.e., convolution by a BRIR) on behavioral and cerebral processing has so far received surprisingly little attention

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Conclusion