title: Extended Broca's area in the functional connectome of language in adults: combined cortical and subcortical single-subject analysis using fMRI and DTI tractography.
abstract: Traditional models of the human language circuitry encompass three cortical areas, Broca's, Geschwind's and Wernicke's, and their connectivity through white matter fascicles. The neural connectivity deep to these cortical areas remains poorly understood, as does the macroscopic functional organization of the cortico-subcortical language circuitry. In an effort to expand current knowledge, we combined functional MRI (fMRI) and diffusion tensor imaging to explore subject-specific structural and functional macroscopic connectivity, focusing on Broca's area. Fascicles were studied using diffusion tensor imaging fiber tracking seeded from volumes placed manually within the white matter. White matter fascicles and fMRI-derived clusters (antonym-generation task) of positive and negative blood-oxygen-level-dependent (BOLD) signal were co-registered with 3-D renderings of the brain in 12 healthy subjects. Fascicles connecting BOLD-derived clusters were analyzed within specific cortical areas: Broca's, with the pars triangularis, the pars opercularis, and the pars orbitaris; Geschwind's and Wernicke's; the premotor cortex, the dorsal supplementary motor area, the middle temporal gyrus, the dorsal prefrontal cortex and the frontopolar region. We found a functional connectome divisible into three systems-anterior, superior and inferior-around the insula, more complex than previously thought, particularly with respect to a new extended Broca's area. The extended Broca's area involves two new fascicles: the operculo-premotor fascicle comprised of well-organized U-shaped fibers that connect the pars opercularis with the premotor region; and (2) the triangulo-orbitaris system comprised of intermingled U-shaped fibers that connect the pars triangularis with the pars orbitaris. The findings enhance our understanding of language function.
authors.affiliation: Surgical Planning Laboratory, Harvard Medical School, Boston, MA, USA. jjlemaire@chu-clermontferrand.fr
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Lemaire
authors.forename: Alexandra
authors.initials: A
authors.lastname: Golby
authors.forename: William M
authors.initials: WM
authors.lastname: Wells
authors.forename: Sonia
authors.initials: S
authors.lastname: Pujol
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Tie
authors.forename: Laura
authors.initials: L
authors.lastname: Rigolo
authors.forename: Alexander
authors.initials: A
authors.lastname: Yarmarkovich
authors.forename: Steve
authors.initials: S
authors.lastname: Pieper
authors.forename: Carl-Fredrik
authors.initials: CF
authors.lastname: Westin
authors.forename: Ferenc
authors.initials: F
authors.lastname: Jolesz
authors.forename: Ron
authors.initials: R
authors.lastname: Kikinis
mesh_terms: D000328:Adult; D016880:Anisotropy; D063132:Connectome; D056324:Diffusion Tensor Imaging; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply* / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008279:Magnetic Resonance Imaging; D008297:Male; D009413:Nerve Fibers, Myelinated; D009434:Neural Pathways / Q000098:blood supply / Q000502:physiology; D010100:Oxygen / Q000097:blood; D055815:Young Adult
chemical_list: D010100:Oxygen