title: The neural code for face orientation in the human fusiform face area.
abstract: Humans recognize faces and objects with high speed and accuracy regardless of their orientation. Recent studies have proposed that orientation invariance in face recognition involves an intermediate representation where neural responses are similar for mirror-symmetric views. Here, we used fMRI, multivariate pattern analysis, and computational modeling to investigate the neural encoding of faces and vehicles at different rotational angles. Corroborating previous studies, we demonstrate a representation of face orientation in the fusiform face-selective area (FFA). We go beyond these studies by showing that this representation is category-selective and tolerant to retinal translation. Critically, by controlling for low-level confounds, we found the representation of orientation in FFA to be compatible with a linear angle code. Aspects of mirror-symmetric coding cannot be ruled out when FFA mean activity levels are considered as a dimension of coding. Finally, we used a parametric family of computational models, involving a biased sampling of view-tuned neuronal clusters, to compare different face angle encoding models. The best fitting model exhibited a predominance of neuronal clusters tuned to frontal views of faces. In sum, our findings suggest a category-selective and monotonic code of face orientation in the human FFA, in line with primate electrophysiology studies that observed mirror-symmetric tuning of neural responses at higher stages of the visual system, beyond the putative homolog of human FFA.
authors.affiliation: Bernstein Center for Computational Neuroscience, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany, Berlin School of Mind and Brain, Humboldt Universität zu Berlin, 10099 Berlin, Germany, and Berlin Center for Advanced Neuroimaging, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany toporam@gmail.com.
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Ramírez
authors.affiliation: Bernstein Center for Computational Neuroscience, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany, Berlin School of Mind and Brain, Humboldt Universität zu Berlin, 10099 Berlin, Germany, and Berlin Center for Advanced Neuroimaging, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany.
authors.forename: Radoslaw M
authors.initials: RM
authors.lastname: Cichy
authors.affiliation: Bernstein Center for Computational Neuroscience, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany, Berlin Center for Advanced Neuroimaging, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany.
authors.forename: Carsten
authors.identifier: http://orcid.org/0000-0002-1037-2735
authors.initials: C
authors.lastname: Allefeld
authors.affiliation: Bernstein Center for Computational Neuroscience, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany, Berlin School of Mind and Brain, Humboldt Universität zu Berlin, 10099 Berlin, Germany, and Berlin Center for Advanced Neuroimaging, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany.
authors.forename: John-Dylan
authors.initials: JD
authors.lastname: Haynes
mesh_terms: D000328:Adult; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D018986:Motor Vehicles; D010364:Pattern Recognition, Visual; D012399:Rotation; D014793:Visual Cortex / Q000502:physiology*
keywords: fMRI; face recognition; invariance; mirror symmetry; object recognition; orientation encoding