Through the looking-glass: Neural basis of self representation during speech perception A V AV AVi AV AVi Results -Self

International audienceIntroduction:To recognize one's own face and voice is key for our self-awareness and for our ability to communicateeffectively with others. Interestingly, several theories and studies suggest that self-recognition duringaction observation may partly result from a functional coupling between action and perception systemsand a better integration of sensory inputs with our own sensory-motor knowledge (Apps & Tsakiris,2014). The present fMRI study aimed at further investigating the neural basis of self representationduring auditory, visual and audio-visual speech perception. Our working hypothesis was that hearingand/or viewing oneself talk might activate sensory-motor plans to a greater degree than does observingothers.Methods:• Participants were 12 healthy adults (25±6years, 9 females).• A total of 1176 stimuli were created. During the scanning session, participants were asked to passivelylistening and/or viewing auditory (A), visual (V), audio-visual (AV) and incongruent audio-visual (AVi)syllables. Half of the stimuli were related to themselves, the other half to an unknown speaker, and theywere either presented with or without noise. In addition, a resting face of the participant or of theunknown speaker, presented with and without acoustic noise, served as baseline.• Functional MRI images were acquired with a sparse-sampling acquisition used to minimize scannernoise (53 axial slices, 3 mm3; TR = 8 sec, delay in TR = 5 sec).• BOLD responses were analyzed using a general linear model, including 16 regressors of interest (4modalities x 2 speakers x 2 noise levels) and the 4 corresponding baselines (2 speakers x 2 noiselevels). A second-level random effect group analysis was carried-out, with the modality, the speaker,and the noise level as within-subject factors and the subjects treated as a random factor. All effects andinteractions were calculated with a significance level set at p < .001 uncorrected.Results:• In line with previous brain-imaging studies on multimodal speech perception, the main effect ofmodality revealed stronger activity in the superior temporal auditory regions during A, AV and AVicompared to V, in the middle temporal visual motion area MT/V5 during V, AV, and AVi compared to A,as well as in the premotor cortices during V, AV and AVi compared to A. The main effect of noise and themodality by noise interaction also showed stronger activity in the primary and secondary auditorycortices for the stimuli presented without noise during A, AV and AVi compared to V.• Crucially, the main effect of the speaker showed stronger activity of the left posterior inferior frontalgyrus as well as of the left cerebellum during the observation of self-related stimuli compared to thoserelated to an unknown speaker. In addition, the speaker by noise interaction revealed stronger activityin the ventral superior parietal lobules and the dorsal extrastriate cortices during the observation ofother-related compared to self-related stimuli presented without noise, while the opposite pattern ofactivity was observed for noisy stimuli. Finally, the speaker by modality interaction showed strongeractivity for self-related compared to other-related stimuli during A in the right auditory cortex, as well asstronger activity for other-related compared to self-related stimuli for V, AV and AVi in the left posteriortemporal sulcus.Conclusions:Listening and/or viewing oneself talk was found to activate to a greater extent the left posterior inferiorfrontal gyrus and cerebellum, two regions thought to be responsible for predicting sensory outcomes of action generation constraining perceptual recognition. In addition, activity in associative auditory andvisual brain areas was also found to be modulated by the speaker identity depending on the modality ofpresentation and the acoustic noise. Altogether these results suggest that self-awareness during speechperception is partly driven by afferent and efferent signals in sensory-motor areas