Leroux, G. | bioRxiv Science

bioRxiv2025

How the Brain Distinguishes Internal and External Sounds: An fMRI Investigation of Auditory Sound Externalization

Auditory externalization, the perception of a sound source as located outside the head, is essential for spatial hearing and auditory scene analysis. However, its neural correlates remain poorly understood. This study investigated differences in brain activation elicited by externalized versus internalized sound sources. Twenty-nine healthy participants underwent a 3T functional magnetic resonance imaging (fMRI) scan while listening to auditory stimuli presented in three spatialization conditions: reverberant externalized sounds (highest externalization), anechoic externalized sounds (intermediate externalization) and diotic anechoic sounds (internalized). Whole-brain analyses revealed greater activation for externalized compared to internalized sound sources in the left superior temporal gyrus, including the planum temporale, the cerebellum and the left posterior cingulate gyrus. Internalized sounds elicited greater relative activity in the left inferior temporal gyrus. Direct comparison between the two externalized conditions revealed stronger left superior temporal gyrus activation for reverberant sounds, while anechoic sounds preferentially activated the right middle temporal gyrus. These findings confirmed the key role of the planum temporale in auditory externalization and the involvement of higher-order brain regions, suggesting broader networks underpinning the perception of sound location.

neuroscience↗

bioRxiv2018

Brain areas commonly activated and asymmetrical in production, listening and reading tasks at the word level: an fMRI study of 144 right-handers.

Even if speech perception and production have been revealed to share a common recruitment of both discrete auditory and motor areas, this overlap being also common to reading and listening, no study has investigated the involvement of larger networks in the three tasks yet. So, we first identified the multimodal bilateral brain areas conjointly activated and asymmetrical during listening, production and reading of word-list using fMRI in 144 healthy right-handers (27 years {+/-} 6 years). Such a selection made it possible to unravel 14 regions of the left hemisphere including motor, premotor and inferior parietal cortical areas. On the right, 7 regions were selected, including the posterior Human Voice Area (pHVA). To characterize the network organization within these 21 regions, we then analysed resting-state functional connectivity in 138 of the same participants. It allowed us to segregate a network of executive areas in relation with task completion from a bilateral WORD_CORE network composed of (1) all left areas supporting the action-perception cycle, in which articulatory gestures are the central motor units on which word perception, production, but also reading, would develop and act together according to the motor theory of speech; (2) the right pHVA, acting as a prosodic integrative area, underpinning the intertwining across hemispheres between prosodic (pHVA) and phonemic (left SMG) processing. The present results show that word processing, whatever the language modality involved, is based on a network of plurimodal areas hosting processes specific to each hemisphere and on their cooperation built upon synchronisation at rest.

neuroscience↗