title: Excitability of the motor system: A transcranial magnetic stimulation study on singing and speaking.
abstract: The perception of movements is associated with increased activity in the human motor cortex, which in turn may underlie our ability to understand actions, as it may be implicated in the recognition, understanding and imitation of actions. Here, we investigated the involvement and lateralization of the primary motor cortex (M1) in the perception of singing and speech. Transcranial magnetic stimulation (TMS) was applied independently for both hemispheres over the mouth representation of the motor cortex in healthy participants while they watched 4-s audiovisual excerpts of singers producing a 2-note ascending interval (singing condition) or 4-s audiovisual excerpts of a person explaining a proverb (speech condition). Subjects were instructed to determine whether a sung interval/written proverb, matched a written interval/proverb. During both tasks, motor evoked potentials (MEPs) were recorded from the contralateral mouth muscle (orbicularis oris) of the stimulated motor cortex compared to a control task. Moreover, to investigate the time course of motor activation, TMS pulses were randomly delivered at 7 different time points (ranging from 500 to 3500 ms after stimulus onset). Results show that stimulation of the right hemisphere had a similar effect on the MEPs for both the singing and speech perception tasks, whereas stimulation of the left hemisphere significantly differed in the speech perception task compared to the singing perception task. Furthermore, analysis of the MEPs in the singing task revealed that they decreased for small musical intervals, but increased for large musical intervals, regardless of which hemisphere was stimulated. Overall, these results suggest a dissociation between the lateralization of M1 activity for speech perception and for singing perception, and that in the latter case its activity can be modulated by musical parameters such as the size of a musical interval.
authors.affiliation: Department of Psychology, Université de Montréal, Montreal, Quebec, Canada; International Laboratory for Brain, Music and Sound Research (BRAMS), Université de Montréal, Montreal, Canada; Center for Research on Brain, Language & Music (CRBLM), McGill University, Montreal, Quebec, Canada; Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Université de Montréal, Montréal, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Royal
authors.affiliation: International Laboratory for Brain, Music and Sound Research (BRAMS), Université de Montréal, Montreal, Canada.
authors.forename: Pascale
authors.initials: P
authors.lastname: Lidji
authors.affiliation: Department of Psychology, Université de Montréal, Montreal, Quebec, Canada; Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Université de Montréal, Montréal, Canada.
authors.forename: Hugo
authors.initials: H
authors.lastname: Théoret
authors.affiliation: Science of Music, Auditory Research and Technology Laboratory (SMART), Ryerson University, Canada.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Russo
authors.affiliation: Department of Psychology, Université de Montréal, Montreal, Quebec, Canada; International Laboratory for Brain, Music and Sound Research (BRAMS), Université de Montréal, Montreal, Canada; Center for Research on Brain, Language & Music (CRBLM), McGill University, Montreal, Quebec, Canada; Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Université de Montréal, Montréal, Canada. Electronic address: isabelle.peretz@umontreal.ca.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Peretz
mesh_terms: D000328:Adult; D004292:Dominance, Cerebral / Q000502:physiology*; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D063346:Singing; D013067:Speech Perception / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014705:Verbal Behavior / Q000502:physiology; D055815:Young Adult
keywords: Motor evoked potentials (MEPs); Orbicularis oris; Primary motor cortex (M1); Singing perception; Speech perception; Transcranial magnetic stimulation (TMS)