title: Single-subject analyses of magnetoencephalographic evoked responses to the acoustic properties of affective non-verbal vocalizations.
abstract: Magneto-encephalography (MEG) was used to examine the cerebral response to affective non-verbal vocalizations (ANVs) at the single-subject level. Stimuli consisted of non-verbal affect bursts from the Montreal Affective Voices morphed to parametrically vary acoustical structure and perceived emotional properties. Scalp magnetic fields were recorded in three participants while they performed a 3-alternative forced choice emotion categorization task (Anger, Fear, Pleasure). Each participant performed more than 6000 trials to allow single-subject level statistical analyses using a new toolbox which implements the general linear model (GLM) on stimulus-specific responses (LIMO-EEG). For each participant we estimated "simple" models [including just one affective regressor (Arousal or Valence)] as well as "combined" models (including acoustical regressors). Results from the "simple" models revealed in every participant the significant early effects (as early as ~100 ms after onset) of Valence and Arousal already reported at the group-level in previous work. However, the "combined" models showed that few effects of Arousal remained after removing the acoustically-explained variance, whereas significant effects of Valence remained especially at late stages. This study demonstrates (i) that single-subject analyses replicate the results observed at early stages by group-level studies and (ii) the feasibility of GLM-based analysis of MEG data. It also suggests that early modulation of MEG amplitude by affective stimuli partly reflects their acoustical properties.
authors.affiliation: Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow Glasgow, UK.
authors.forename: Emilie
authors.initials: E
authors.lastname: Salvia
authors.affiliation: Bangor Imaging Unit, School of Psychology, Bangor University Gwynedd, UK.
authors.forename: Patricia E G
authors.initials: PE
authors.lastname: Bestelmeyer
authors.affiliation: School of Psychological Sciences, University of Manchester Manchester, UK ; Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany.
authors.forename: Sonja A
authors.initials: SA
authors.lastname: Kotz
authors.affiliation: Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow Glasgow, UK.
authors.forename: Guillaume A
authors.initials: GA
authors.lastname: Rousselet
authors.affiliation: Brain Research Imaging Center, Division of Clinical Neurosciences, Western General Hospital, University of Edinburgh Edinburgh, UK.
authors.forename: Cyril R
authors.initials: CR
authors.lastname: Pernet
authors.affiliation: Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow Glasgow, UK.
authors.forename: Joachim
authors.initials: J
authors.lastname: Gross
authors.affiliation: Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow Glasgow, UK ; Départment de Psychologie, Université de Montréal Montreal, Canada ; Institut des Neurosciences de La Timone, UMR 7289, CNRS & Aix-Marseille Université Marseille, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Belin
keywords: ANVs; GLM; acoustics; emotions; magneto-encephalography; single-subject; voice morphing