Presentation
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Auditory brain asymmetry as a specialization for actions and materials
Poster D63 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
Paul Lalande-Robert1, Robert Zatorre2, Akanksha Gupta1, Julien Sein3, Jean-Luc Anton3, Pascal Belin3, Étienne Thoret4, Benjamin Morillon1; 1AMU-INS, 2MNI, 3AMU-INT, 4PRISM/LIS
Auditory hemispheric asymmetry is currently best explained under the spectrotemporal modulation (STM) framework. Left and right auditory systems show increased sensitivity for temporal and spectral modulations respectively, whether sounds contain speech and music or not. However, for distinct hemispheric sensitivities to develop, the temporal and spectral modulations must be of ecological significance to the individual, an aspect that is not accounted for in the STM framework. Previous work in psychophysics has highlighted two components of sound generation that are ecologically relevant: the action (friction, impact, …) that impulses some energy, and the material that resonates in response. As actions and materials relate to the temporal dynamic and the spectral structure of a sound respectively, we propose to reframe the distinct hemispheric sensitivity to STMs as a specialization for the processing of actions and materials. First, we analyzed a corpus of environmental sounds in the STM domain. An independent component analysis revealed that temporal and spectral modulations were the two components explaining most of the variance (r2 = 0.801). These modulations are the ones known to drive lateralized brain responses, and their independence suggests that they carry different information, in line with the action/material framework. Then, we synthesized various friction sounds for which action and material content was crossed and balanced, and selectively degraded their temporal or spectral dimensions. In a behavioral experiment (n=20), we show a double dissociation so that discriminating actions rely on temporal modulations only, and spectral modulations rely on spectral modulations only. Finally, we recorded the brain activity of the same 20 participants with functional MRI (3T Prisma Siemens, fast event-related sparse sampling) while they listened to the sounds from Experiment 2. We conducted multivariate pattern analyses (MVPA) with a whole-brain searchlight procedure. Cluster-based permutation tests revealed that actions are encoded in the left auditory cortex (p = 0.002) as well as in the left inferior frontal gyrus (p = 0.006). In contrast, materials are encoded in the right auditory cortex (p = 0.036). We conclude that (1) environmental sounds are composed of an independent mixture of temporal and spectral modulations as expected under the action/material framework, (2) action and material perception rely on temporal and spectral modulations respectively, and (3) action and material are encoded in left and right auditory systems respectively. We propose that action and material are the two ecologically relevant auditory domains that led to the development of distinct hemispheric sensitivities to STMs.
Topic Areas: Speech Perception,