P 151. The right (but not the left) lateral occipital complex is causally implicated in visual mirror symmetry detection: An fMRI-guided TMS study

Abstract

Despite the fact that bilateral mirror symmetry is an important characteristic of the visual world, few studies have investigated its neural basis. Here we addressed this issue by investigating whether the object-selective lateral occipital cortex (LO), a key brain region in object and shape processing, is causally involved in this kind of symmetry detection. Participants were asked to discriminate between symmetric and asymmetric dot patterns, while fMRI-guided repetitive TMS was delivered online over either the left LO, the right LO or two control sites in the occipital cortex. We found that the application of TMS over the right LO slowed down symmetry judgments, whereas stimulation of the left LO, or of two control sites, had no impact. Our results thus indicate that the right (but not the left) LO is causally implicated in symmetry detection. This finding may relate to the previously reported right-hemisphere lateralization of holistic processing of stimuli, including faces for which symmetry is a critical cue.