title: Hand gestures as visual prosody: BOLD responses to audio-visual alignment are modulated by the communicative nature of the stimuli.
abstract: During public addresses, speakers accompany their discourse with spontaneous hand gestures (beats) that are tightly synchronized with the prosodic contour of the discourse. It has been proposed that speech and beat gestures originate from a common underlying linguistic process whereby both speech prosody and beats serve to emphasize relevant information. We hypothesized that breaking the consistency between beats and prosody by temporal desynchronization, would modulate activity of brain areas sensitive to speech-gesture integration. To this aim, we measured BOLD responses as participants watched a natural discourse where the speaker used beat gestures. In order to identify brain areas specifically involved in processing hand gestures with communicative intention, beat synchrony was evaluated against arbitrary visual cues bearing equivalent rhythmic and spatial properties as the gestures. Our results revealed that left MTG and IFG were specifically sensitive to speech synchronized with beats, compared to the arbitrary vision-speech pairing. Our results suggest that listeners confer beats a function of visual prosody, complementary to the prosodic structure of speech. We conclude that the emphasizing function of beat gestures in speech perception is instantiated through a specialized brain network sensitive to the communicative intent conveyed by a speaker with his/her hands.
authors.affiliation: Multisensory Research Group, Center for Brain and Cognition, Universitat Pompeu Fabra, Barcelona, Spain. Electronic address: emmanuel.biau@gmail.com.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Biau
authors.affiliation: Multisensory Research Group, Center for Brain and Cognition, Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Morís Fernández
authors.affiliation: Department of Psychology, University of Hull, UK.
authors.forename: Henning
authors.initials: H
authors.lastname: Holle
authors.affiliation: Department of Psychology, Universitat Jaume I, Castelló de la Plana, Spain.
authors.forename: César
authors.initials: C
authors.lastname: Avila
authors.affiliation: Multisensory Research Group, Center for Brain and Cognition, Universitat Pompeu Fabra, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
authors.forename: Salvador
authors.initials: S
authors.lastname: Soto-Faraco
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D003463:Cues; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D005868:Gestures; D006225:Hand; D006801:Humans; D008037:Linguistics; D008279:Magnetic Resonance Imaging; D008297:Male; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Audiovisual speech; Gestures; MTG; Multisensory Integration; Speech perception; fMRI