title: Asymmetry of parietal interhemispheric connections in humans.
abstract: Visuospatial abilities are preferentially mediated by the right hemisphere. Although this asymmetry of function is thought to be due to an unbalanced interaction between cerebral hemispheres, the underlying neurophysiological substrate is still largely unknown. Here, using a method of trifocal transcranial magnetic stimulation, we show that the right, but not left, human posterior parietal cortex exerts a strong inhibitory activity over the contralateral homologous area by a short-latency connection. We also clarify, using diffusion-tensor magnetic resonance imaging, that such an interaction is mediated by direct transcallosal projections located in the posterior corpus callosum. We argue that this anatomo-functional network may represent a possible neurophysiological basis for the ongoing functional asymmetry between parietal cortices, and that its damage could contribute to the clinical manifestations of neglect.
authors.affiliation: Laboratory of Clinical and Behavioural Neurology, Santa Lucia Foundation IRCCS, 00179 Rome, Italy. g.koch@hsantalucia.it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
authors.forename: Mara
authors.initials: M
authors.lastname: Cercignani
authors.forename: Sonia
authors.initials: S
authors.lastname: Bonnì
authors.forename: Viola
authors.initials: V
authors.lastname: Giacobbe
authors.forename: Giulia
authors.initials: G
authors.lastname: Bucchi
authors.forename: Viviana
authors.initials: V
authors.lastname: Versace
authors.forename: Carlo
authors.initials: C
authors.lastname: Caltagirone
authors.forename: Marco
authors.initials: M
authors.lastname: Bozzali
mesh_terms: D000328:Adult; D016880:Anisotropy; D001931:Brain Mapping; D003337:Corpus Callosum / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging; D004558:Electric Stimulation; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D038361:Neuronavigation / Q000379:methods; D010296:Parietal Lobe / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult