Abstract
Introduction FMRI studies have suggested that the right posterior superior temporal sulcus (pSTS) constitutes an important node of a face-selective network required for facial expression recognition. The role of the left pSTS has not been, however, that well investigated. We performed fMRI and TMS studies to investigate the extent to which facial expression recognition in the pSTS is lateralised across hemispheres. FMRI Study A large gender-balanced group of participants (N=52) was scanned while they watched short videos of faces and objects to functionally localize face-selective regions in the whole brain and then compare activation in right and left pSTS with activation in other face-selective regions. Results (Figure) revealed that: - face-selective regions (defined as activation for faces > objects), including pSTS, were present in both hemispheres but they were larger and more consistently found in the right hemisphere; - the right lateralization in pSTS was greater compared to other face-selective regions. These results demonstrate that faces are preferentially processed in the right hemisphere and that the pSTS is the strongest driver of this laterality. TMS Study The hemispheric involvement of pSTS in face recognition was further investigated using TMS. TMS was was delivered to the right and left face-selective pSTS, functionally localised in the fMRI Study, while participants (N=20) performed a facial emotion discrimination task or object discrimination task. Analyses of accuracy data showed that: - TMS over right pSTS impaired discrimination of facial expressions significantly stronger (p>.001, corrected) and more consistently (in 18 out of 20 participants) than TMS over left pSTS (p=.08, corrected; in 13 out of 20 participants); - TMS had no effect when applied to these homologous regions or a control condition during object recognition task. These results further support the importance of pSTS in face recognition and strong lateralisation of this process in pSTS.
Meeting abstract presented at VSS 2018