The causal role of the lateral occipital complex in visual mirror symmetry detection and grouping: An fMRI-guided TMS study

Silvia Bona, Andrew Herbert, Carlo Toneatto, Juha Silvanto, Zaira Cattaneo

Research output: Contribution to journalArticle


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 (LO) cortex, a key brain region in object and shape processing, is causally involved in bilateral 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 both right and left LO impaired symmetry judgments, with disruption being greater following right LO than left LO TMS, indicative of right hemisphere lateralization in symmetry processing. TMS over LO bilaterally also affected a visual contour detection task, with no evidence for hemispheric difference in this task. Overall, our results demonstrates that LO bilaterally plays a causal role in symmetry detection possibly due to symmetry acting as a strong cue in Gestalt processes mediating object recognition.

Original languageEnglish
Pages (from-to)46-55
Number of pages10
Issue number1
Publication statusPublished - Feb 2014



  • Bilateral mirror symmetry
  • Lateralization
  • LO
  • Shape detection
  • Symmetry detection
  • TMS
  • Visual cortex

ASJC Scopus subject areas

  • Clinical Neurology
  • Neurology
  • Arts and Humanities (miscellaneous)
  • Developmental and Educational Psychology
  • Experimental and Cognitive Psychology
  • Neuropsychology and Physiological Psychology
  • Cognitive Neuroscience

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