Localization of facial symmetry perception through FMRI

Yıldırım, Funda
Humans are extremely sensitive and accurate about detecting the amount of symmetry that a face possesses. However perception of facial symmetry has not been investigated in terms of its neural correlates yet. In this thesis, we investigated localization of facial symmetry perception in the brain through the use of the fMR adaptation method. In this method, marginally active neuronal populations can be detected by presenting faces with varying symmetry. By standardizing all aspects of the faces such as illumination, pose and contrast, we manipulated only the amount of fluctuating asymmetry in the face images. Previous studies have shown that a specific area, lateral occipital complex (LOC) exhibits sensitivity to orientation and position changes to faces and other objects. We observed that facial symmetry activation is specifically localized within the LOC boundaries. Within the LOC, we found that previously defined areas namely LO1 and LO2 are both responsive to manipulations of facial symmetry. We also tested our fMR-adaptation paradigm on non-face images, generated by scrambling the face stimuli used in our experiments. We replicated earlier results which demonstrated that LO1 and LO2 are activated in detecting differences between symmetric versus asymmetric patches. This suggests that although facial symmetry perception is not processed by a function specific area of the LOC, it uses main resources allocated for the object recognition system in an efficient manner. To the best of our knowledge, our study is the first to investigate face symmetry perception through fMR-adaptation.
Citation Formats
F. Yıldırım, “Localization of facial symmetry perception through FMRI,” M.S. - Master of Science, Middle East Technical University, 2012.