title: The causal role of the occipital face area (OFA) and lateral occipital (LO) cortex in symmetry perception.
abstract: Symmetry is an important cue in face and object perception. Here we used fMRI-guided transcranial magnetic stimulation (TMS) to shed light on the role of the occipital face area (OFA), a key region in face processing, and the lateral occipital (LO) cortex, a key area in object processing, in symmetry detection. In the first experiment, we applied TMS over the rightOFA, its left homolog (leftOFA), rightLO, and vertex (baseline) while participants were discriminating between symmetric and asymmetric dot patterns. Stimulation of rightOFA and rightLO impaired performance, causally implicating these two regions in detection of symmetry in low-level dot configurations. TMS over rightLO but not rightOFA also significantly impaired detection of nonsymmetric shapes defined by collinear Gabor patches, demonstrating that rightOFA responds to symmetry but not to all cues mediating figure-ground segregation. The second experiment showed a causal role for rightOFA but not rightLO in facial symmetry detection. Overall, our results demonstrate that both the rightOFA and rightLO are sensitive to symmetry in dot patterns, whereas only rightOFA is causally involved in facial symmetry detection.
authors.affiliation: Brain Research Unit, O.V. Lounasmaa Laboratory, School of Science, Aalto University, 02150 Espoo, Finland, Advanced Magnetic Imaging Centre, Aalto Neuroimaging, OV Lounasmaa Laboratory, School of Science, Aalto University, 00076 Espoo, Finland, BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Central Hospital, 00290 Helsinki, Finland, Department of Behavioural Sciences, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Silvia
authors.initials: S
authors.lastname: Bona
authors.affiliation: Department of Psychology, University of Milano-Bicocca, 20126 Milan, Italy, Brain Connectivity Center, National Neurological Institute C. Mondino, 27100 Pavia, Italy, Milan Center for Neuroscience, 20126 Milan, Italy, zaira.cattaneo@unimib.it.
authors.forename: Zaira
authors.identifier: http://orcid.org/0000-0001-7516-7508
authors.initials: Z
authors.lastname: Cattaneo
authors.affiliation: Brain Research Unit, O.V. Lounasmaa Laboratory, School of Science, Aalto University, 02150 Espoo, Finland, University of Westminster, Faculty of Science and Technology, Department of Psychology, W1B 2HW London, United Kingdom, and.
authors.forename: Juha
authors.initials: J
authors.lastname: Silvanto
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005145:Face / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010364:Pattern Recognition, Visual; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*
keywords: bilateral symmetry; fMRI-guided TMS; lateral occipital cortex; occipital face area; symmetry detection; visual cortex