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The time and space of lexicality: a neuromagnetic view

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Abstract

Illuminating the neural mechanisms subserving lexico-semantic processing is requisite to further understanding the neurophysiological basis of the dyslexias. Yet, despite numerous functional neuroimaging experiments, the location and temporal behavior of brain regions mediating word-level language processing remain an area of debate. Such investigations typically utilize the word/pseudoword contrast within hemodynamic measurements, and report several left hemisphere regions that respond more strongly to pseudowords but fail to replicate neural areas unique to real word processing. The present experiment addressed this problem from a different perspective. Mainly, we hypothesized that the time course, but not the neuroanatomy, would show within-subject across-condition disparities. For that purpose, we applied dipole-modeling techniques to high-density magnetoencephalographic recordings of healthy subjects, and utilized excellent spatiotemporal accuracy to demonstrate significant across-condition differences in the time domain, along with indistinguishable neural correlates within-subject. In all participants, both words and pseudowords elicited activity in left perisylvian language areas, with words consistently activating these regions ~100 ms earlier than pseudowords. Considerable functional heterogeneity was also observed, and this might underlie the inconsistencies among previous studies. We conclude that the neural distinction in word/pseudoword processing is not in spatial localization, but is better conceptualized as a dynamic difference in processing time.

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Acknowledgements

TWW was supported by a pre-doctoral traineeship through the Center for Cognitive Sciences (NIH training grant T32 HD007151). Funding for ACL and PJP was provided by the Mental Illness and Neuroscience Discovery (MIND) Institute. This work was also supported by the US Department of Veterans Affairs, the American Legion Auxiliary, and the American Legion Brain Sciences Chair.

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Authors and Affiliations

  1. Brain Sciences Center, Minneapolis Veterans Affairs Medical Center (VAMC), One Veterans Drive-11-B, Minneapolis, MN 55417, USA

    Tony W. Wilson, Arthur C. Leuthold, Scott M. Lewis, Apostolos P. Georgopoulos & Patricia J. Pardo

  2. The Domenici Research Center for Mental Illness, Veterans Affairs Medical Center, Minneapolis, MN 55417, USA

    Tony W. Wilson, Arthur C. Leuthold, Scott M. Lewis, Apostolos P. Georgopoulos & Patricia J. Pardo

  3. Center for Cognitive Sciences, University of Minnesota, Minneapolis, MN 55455, USA

    Tony W. Wilson & Apostolos P. Georgopoulos

  4. Department of Psychology, University of Minnesota, Minneapolis, MN 55455, USA

    Tony W. Wilson & Patricia J. Pardo

  5. Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA

    Arthur C. Leuthold & Apostolos P. Georgopoulos

  6. Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA

    Arthur C. Leuthold, Scott M. Lewis & Apostolos P. Georgopoulos

  7. Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA

    Scott M. Lewis & Apostolos P. Georgopoulos

  8. Department of Psychiatry, University of Minnesota, Minneapolis, MN 55454, USA

    Apostolos P. Georgopoulos & Patricia J. Pardo

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  1. Tony W. Wilson
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  2. Arthur C. Leuthold
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  3. Scott M. Lewis
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Correspondence to Patricia J. Pardo.

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Wilson, T.W., Leuthold, A.C., Lewis, S.M. et al. The time and space of lexicality: a neuromagnetic view. Exp Brain Res 162, 1–13 (2005). https://doi.org/10.1007/s00221-004-2099-3

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  • DOI: https://doi.org/10.1007/s00221-004-2099-3

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