title: A TMS Investigation on the Role of Lateral Occipital Complex and Caudal Intraparietal Sulcus in the Perception of Object Form and Orientation.
abstract: We used TMS to assess the causal roles of the lateral occipital (LO) and caudal intraparietal sulcus (cIPS) areas in the perceptual discrimination of object features. All participants underwent fMRI to localize these areas using a protocol in which they passively viewed images of objects that varied in both form and orientation. fMRI identified six significant brain regions: LO, cIPS, and the fusiform gyrus, bilaterally. In a separate experimental session, we applied TMS to LO or cIPS while the same participants performed match-to-sample form or orientation discrimination tasks. Compared with sham stimulation, TMS to either the left or right LO increased RTs for form but not orientation discrimination, supporting a critical role for LO in form processing for perception- and judgment-based tasks. In contrast, we did not observe any effects when we applied TMS to cIPS. Thus, despite the clear functional evidence of engagement for both LO and cIPS during the passive viewing of objects in the fMRI experiment, the TMS experiment revealed that cIPS is not critical for making perceptual judgments about their form or orientation.
authors.affiliation: La Trobe University, Melbourne, Australia.|University of Western Ontario, Canada.
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Chouinard
authors.affiliation: University of Saskatchewan, Canada.
authors.forename: Deiter K
authors.initials: DK
authors.lastname: Meena
authors.affiliation: University of British Columbia, Canada.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Whitwell
authors.affiliation: University of Toronto, Canada.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Hilchey
authors.affiliation: La Trobe University, Melbourne, Australia.|University of Western Ontario, Canada.
authors.forename: Melvyn A
authors.initials: MA
authors.lastname: Goodale
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009778:Occipital Lobe / Q000502:physiology*; D010296:Parietal Lobe / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult