Variability and asymmetry of the sulcal contours defining Broca's area homologue in the chimpanzee brain

Authors

  • Simon S. Keller,

    Corresponding author
    1. The Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, UK
    2. The Department of Neurology, University of Münster, D-48129 Münster, Germany
    • The Department of Clinical Neuroscience, Institute of Psychiatry, Box PO43, De Crespigny Park, King's College London, SE5 8AF, UK
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  • Michael Deppe,

    1. The Department of Neurology, University of Münster, D-48129 Münster, Germany
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  • Marc Herbin,

    1. UMR 7179 USM301 MNHN-CNRS, Museum National d'Histoire Naturelle, 75231 Paris cedex 05, France
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  • Emmanuel Gilissen

    1. Royal Museum for Central Africa, 3080 Tervuren, Belgium
    2. Laboratory of Histology and Neuropathology, Université Libre de Bruxelles, B-1050 Brussels, Belgium
    3. Department of Anthropology, University of Arkansas, Fayetteville, Arkansas 72701
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Abstract

There has been recent motivation to search for neuroanatomical asymmetries in nonhuman primates in order to provide comparative information on how the human brain is structurally organized to support specific cognitive capabilities, such as language functions. We took the opportunity to study Broca's area homologue in a novel sample of 80 preserved postmortem chimpanzee (Pan troglodytes) cerebral hemispheres. Consistent with the only prior study documenting the morphology of Broca's area homologue in the chimpanzee (Sherwood et al. [2003] Anat Rec 271:276–285), we report great interindividual variation in the structure and connections of the sulci investigated, most notably a left-sided bias in the bifurcation of the inferior precentral sulcus, an anatomical feature that occurs much more frequently in chimpanzees relative to humans. Consistent with our recent neuroimaging report (Keller et al. [2009b] J Neurosci 29:14607–14616), no population-based interhemispheric asymmetries of sulcal length existed that could be considered markers of the size of Broca's area homologue. With strict anatomical guidelines, we report that the diagonal sulcus was present in 25% left and 20% right chimpanzee hemispheres studied, which is substantially less that the general prevalence in humans. Through the presentation of schematic drawings, photographs, morphological recordings and sulcal length metrics, our data illustrate the interindividual variability of Broca's area homologue in the chimpanzee and support the notion of no macroscopic asymmetry of this important homologous language brain region in one of the closest evolutionary ancestor to modern humans J. Comp. Neurol. 520:1165–1180, 2012. © 2011 Wiley Periodicals, Inc.

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