Research Report Involvement of low-level visual areas in hemispheric superiority for face processing Yul-Wan Sung a, b, c , ⁎ , Yoshiaki Someya b , Yamamoto Eriko b , Sang-Han Choi c , Zang-Hee Cho c , Seiji Ogawa a, b, c a Kansei Fukushi Research Institute, Tohoku Fukushi University, Sendai, Japan b Center for Advanced Research for Logic and Sensibility, Keio University, Tokyo, Japan c Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea ARTICLE INFO ABSTRACT Article history: Accepted 21 March 2011 Available online 13 April 2011 Previous studies on laterality in face processing have indicated superiority of the right hemisphere in discriminating and recognizing faces; however, the reasons for this feature are poorly understood. We employed functional MRI (fMRI) to elucidate the origin of this feature and used a paired-stimulus paradigm in which face pairs were presented unilaterally at the left or right visual hemifield of the participants. Each face in a pair was at a different position in the visual field. Refractory suppression in the fMRI response was observed bilaterally at the fusiform face area (FFA) for the same face pairs when pictures were presented in the left visual hemifield. In contrast, suppression was observed bilaterally at the FFA for the different as well as for the same face pairs when pictures were presented in the right visual hemifield. This pattern indicated inferior discrimination ability for paired stimuli presented to the right visual hemifield. These observations, along with changes in bilaterally interlocked responses at the FFA, suggest that low-level visual areas, and not high-level face areas, are strongly associated with the superiority of the right hemisphere in face processing. © 2011 Elsevier B.V. All rights reserved. Keywords: Hemispheric superiority Visual hemifield Face processing Refractory suppression Functional MRI (fMRI) 1. Introduction The right hemisphere exhibits superiority with regard to perception and recognition of faces (Leehey et al., 1978; Miller et al., 2002; Wilkinson et al., 2009). However the reasons behind this feature remain to be elucidated. Two specialized areas in the occipital and temporal regions, occipital face areas (OFA) and fusiform face area (FFA), play crucial roles in face processing (Kanwisher et al., 1997). Another area in the temporal region is involved in higher processing such as that for facial emotions and expression, while the orbitofrontal gyrus also shows an area for retrieving face information when recalling faces (Ishai, 2008; Summerfield et al., 2006). To discover the laterality- processing mechanism for faces, we investigated the influ- ence of hemispheric differences in individuating faces with regard to the involvement of face-selective and/or low-level visual areas showing noncategorical selectivity. Through traditional functional MRI (fMRI) paradigms it is difficult to obtain functional information for discriminating neuronal structures activated by individual faces because of the spatial resolution limitation of MRI. Hence, we used an fMRI paradigm inducing refractory suppression to investigate face individu- ation in face-selective areas. Refractory suppression has been BRAIN RESEARCH 1390 (2011) 118 – 125 ⁎ Corresponding author at: Kansei Fukushi Research Institute, Tohoku Fukushi University, 6-149-1 Kunimi, Aoba, Sendai 989-3201, Japan. Fax: +81 22 728 7433. E-mail address: sungstone@gmail.com (Y.-W. Sung). 0006-8993/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2011.03.049 available at www.sciencedirect.com www.elsevier.com/locate/brainres