Spatial MEG Laterality maps for language: Clinical applications in epilepsy

Authors

  • Ryan C.N. D'Arcy,

    Corresponding author
    1. Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada
    2. IWK Health Sciences Centre, Halifax, Nova Scotia, Canada
    3. Department of Radiology, Dalhousie University, Halifax, Nova Scotia, Canada
    4. Department of Psychology/Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
    5. Department of Anatomy and Neurobiology, Dalhousie University, Halifax, Nova Scotia, Canada
    • NRC Institute for Biodiagnostics (Atlantic), 3900-1796 Summer St. Halifax, Nova Scotia, Canada B3A 2A8
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  • Timothy Bardouille,

    1. Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada
    2. IWK Health Sciences Centre, Halifax, Nova Scotia, Canada
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  • Aaron J. Newman,

    1. Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada
    2. IWK Health Sciences Centre, Halifax, Nova Scotia, Canada
    3. Department of Psychology/Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
    4. Department of Medicine (Neurology), Dalhousie University, Halifax, Nova Scotia, Canada
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  • Sean R. McWhinney,

    1. Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada
    2. Department of Psychology/Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
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  • Drew DeBay,

    1. Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada
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  • R. Mark Sadler,

    1. Department of Medicine (Neurology), Dalhousie University, Halifax, Nova Scotia, Canada
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  • David B. Clarke,

    1. Department of Anatomy and Neurobiology, Dalhousie University, Halifax, Nova Scotia, Canada
    2. Department of Surgery (Neurosurgery), Dalhousie University, Halifax, Nova Scotia, Canada
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  • Michael J. Esser

    1. IWK Health Sciences Centre, Halifax, Nova Scotia, Canada
    2. Department of Psychology/Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
    3. Department of Medicine (Neurology), Dalhousie University, Halifax, Nova Scotia, Canada
    4. Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
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Abstract

Functional imaging is increasingly being used to provide a noninvasive alternative to intracarotid sodium amobarbitol testing (i.e., the Wada test). Although magnetoencephalography (MEG) has shown significant potential in this regard, the resultant output is often reduced to a simplified estimate of laterality. Such estimates belie the richness of functional imaging data and consequently limit the potential value. We present a novel approach that utilizes MEG data to compute “complex laterality vectors” and consequently “laterality maps” for a given function. Language function was examined in healthy controls and in people with epilepsy. When compared with traditional laterality index (LI) approaches, the resultant maps provided critical information about the magnitude and spatial characteristics of lateralized function. Specifically, it was possible to more clearly define low LI scores resulting from strong bilateral activation, high LI scores resulting from weak unilateral activation, and most importantly, the spatial distribution of lateralized activation. We argue that the laterality concept is better presented with the inherent spatial sensitivity of activation maps, rather than being collapsed into a one-dimensional index. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.

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