Perisylvian language networks of the human brain

Authors

  • Marco Catani MD,

    Corresponding author
    1. Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, United Kingdom
    • Institute of Psychiatry, PO 89, King's College London, DeCrespigny Park, London SE5 8AZ, United Kingdom
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  • Derek K. Jones PhD,

    1. Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, United Kingdom
    2. Section on Tissue Biophysics and Biomimetics, Laboratory of Integrative Medicine and Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
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  • Dominic H. ffytche MD

    1. Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, United Kingdom
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Abstract

Early anatomically based models of language consisted of an arcuate tract connecting Broca's speech and Wernicke's comprehension centers; a lesion of the tract resulted in conduction aphasia. However, the heterogeneous clinical presentations of conduction aphasia suggest a greater complexity of perisylvian anatomical connections than allowed for in the classical anatomical model. This article re-explores perisylvian language connectivity using in vivo diffusion tensor magnetic resonance imaging tractography. Diffusion tensor magnetic resonance imaging data from 11 right-handed healthy male subjects were averaged, and the arcuate fasciculus of the left hemisphere reconstructed from this data using an interactive dissection technique. Beyond the classical arcuate pathway connecting Broca's and Wernicke's areas directly, we show a previously undescribed, indirect pathway passing through inferior parietal cortex. The indirect pathway runs parallel and lateral to the classical arcuate fasciculus and is composed of an anterior segment connecting Broca's territory with the inferior parietal lobe and a posterior segment connecting the inferior parietal lobe to Wernicke's territory. This model of two parallel pathways helps explain the diverse clinical presentations of conduction aphasia. The anatomical findings are also relevant to the evolution of language, provide a framework for Lichtheim's symptom-based neurological model of aphasia, and constrain, anatomically, contemporary connectionist accounts of language. Ann Neurol 2005

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