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Roberto Caldara, Mohamed Seghier; Symmetry is in the eye of the fusiform face area. Journal of Vision 2006;6(6):668. doi: 10.1167/6.6.668.
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© ARVO (1962-2015); The Authors (2016-present)
Symmetry in objects pervades our visual world, so perhaps it is not surprising that human beings show a strong sensitivity to this geometrical constraint. Among symmetrical objects, the most relevant class of stimuli is undeniably constituted by human faces. Symmetry in faces has often been considered an important property for beauty and genetic fitness, both representing crucial factors for social and biological interactions. At the neural level, we recently demonstrated that particular low-level structural properties shape the responses of the right middle fusiform gyrus (the Fusiform Face Area - FFA), an area showing a preference for faces over objects. The FFA is tuned to curvilinear patterns with more high-contrasted elements in the upper part, a mechanism that might drive the automatic detection of faces in the visual world (Caldara et al., 2006). However, it is still unknown whether and how the neural structures devoted to process faces are sensitive to symmetry. Here, we used functional Magnetic Resonance Imaging to investigate this question. Participants were presented with symmetrical and asymmetrical curvilinear head-shaped patterns with either more elements in the upper or the lower vertical part. These patterns were not perceived as faces. The FFA showed larger activations for curvilinear patterns with more elements in the upper part, replicating our previous observations. Crucially, a violation of symmetry significantly decreased the responses of this neural structure. These findings provide direct evidence that the FFA is tuned for geometrical properties best fitting with the structure of faces and that symmetry finely calibrates such neural tuning.
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