title: Lateralization for dynamic facial expressions in human superior temporal sulcus.
abstract: Most face processing studies in humans show stronger activation in the right compared to the left hemisphere. Evidence is largely based on studies with static stimuli focusing on the fusiform face area (FFA). Hence, the pattern of lateralization for dynamic faces is less clear. Furthermore, it is unclear whether this property is common to human and non-human primates due to predisposing processing strategies in the right hemisphere or that alternatively left sided specialization for language in humans could be the driving force behind this phenomenon. We aimed to address both issues by studying lateralization for dynamic facial expressions in monkeys and humans. Therefore, we conducted an event-related fMRI experiment in three macaques and twenty right handed humans. We presented human and monkey dynamic facial expressions (chewing and fear) as well as scrambled versions to both species. We studied lateralization in independently defined face-responsive and face-selective regions by calculating a weighted lateralization index (LIwm) using a bootstrapping method. In order to examine if lateralization in humans is related to language, we performed a separate fMRI experiment in ten human volunteers including a 'speech' expression (one syllable non-word) and its scrambled version. Both within face-responsive and selective regions, we found consistent lateralization for dynamic faces (chewing and fear) versus scrambled versions in the right human posterior superior temporal sulcus (pSTS), but not in FFA nor in ventral temporal cortex. Conversely, in monkeys no consistent pattern of lateralization for dynamic facial expressions was observed. Finally, LIwms based on the contrast between different types of dynamic facial expressions (relative to scrambled versions) revealed left-sided lateralization in human pSTS for speech-related expressions compared to chewing and emotional expressions. To conclude, we found consistent laterality effects in human posterior STS but not in visual cortex of monkeys. Based on our results, it is tempting to speculate that lateralization for dynamic face processing in humans may be driven by left-hemispheric language specialization which may not have been present yet in the common ancestor of human and macaque monkeys.
authors.affiliation: Research Group Psychiatry, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Old Age Psychiatry Department, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium. Electronic address: francoislaurent.dewinter@med.kuleuven.be.
authors.forename: François-Laurent
authors.initials: FL
authors.lastname: De Winter
authors.affiliation: Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Research Group Psychiatry, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Old Age Psychiatry Department, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Van den Stock
authors.affiliation: Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Nelissen
authors.affiliation: Department of Radiology, UZ Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Imaging & Pathology, KU Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Ronald
authors.initials: R
authors.lastname: Peeters
authors.affiliation: Research Group Psychiatry, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Cognitive Neuroscience, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands; Laboratory for Cognitive and Affective Neuroscience, Tilburg University, P.O. Box 90153, 5000 LE Tilburg, The Netherlands.
authors.forename: Beatrice
authors.initials: B
authors.lastname: de Gelder
authors.affiliation: Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Massachusetts Gen. Hosp., Athinoula A. Martinos Ctr. for Biomed. Imaging, 149 Thirteenth Street, Suite 2301 Charlestown, MA, USA; Dept. of Radiology, Harvard Med. Sch., Boston, MA, USA.
authors.forename: Wim
authors.initials: W
authors.lastname: Vanduffel
authors.affiliation: Research Group Psychiatry, Department of Neurosciences, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Old Age Psychiatry Department, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Vandenbulcke
mesh_terms: D000328:Adult; D000818:Animals; D001931:Brain Mapping; D004644:Emotions / Q000502:physiology; D005149:Facial Expression; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D013045:Species Specificity; D013702:Temporal Lobe / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: Comparative; Dynamic facial expressions; Lateralization; fMRI