Four Functionally Distinct Regions in the Left Supramarginal Gyrus Support Word Processing.
We used fMRI in 85 healthy participants to investigate whether different parts of the left supramarginal gyrus (SMG) are involved in processing phonological inputs and outputs. The experiment involved 2 tasks (speech production (SP) and one-back (OB) matching) on 8 different types of stimuli that systematically varied the demands on sensory processing (visual vs. auditory), sublexical phonological input (words and pseudowords vs. nonverbal stimuli), and semantic content (words and objects vs. pseudowords and meaningless baseline stimuli). In ventral SMG, we found an anterior subregion associated with articulatory sequencing (for SP > OB matching) and a posterior subregion associated with auditory short-term memory (for all auditory > visual stimuli and written words and pseudowords > objects). In dorsal SMG, a posterior subregion was most highly activated by words, indicating a role in the integration of sublexical and lexical cues. In anterior dorsal SMG, activation was higher for both pseudoword reading and object naming compared with word reading, which is more consistent with executive demands than phonological processing. The dissociation of these four "functionally-distinct" regions, all within left SMG, has implications for differentiating between different types of phonological processing, understanding the functional anatomy of language and predicting the effect of brain damage.
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.
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M
Oberhuber
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.
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TMH
Hope
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.|Cognitive Neuroimaging Unit, Emirates College for Advanced Education (ECAE), P.O. Box 126662, Abu Dhabi, UAE.
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ML
Seghier
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.|FMRIB (Oxford Centre for Functional MRI of the Brain), University of Oxford, Oxford, UK.|Wolfson College, University of Oxford, Oxford, UK.
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O
Parker Jones
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.|Collaborative Research Centre 1052 "Obesity Mechanisms", Faculty of Medicine, University Leipzig, Leipzig, Germany.|Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
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Prejawa
Experimental Psychology, Faculty of Brain Sciences, University College London, London, UK.
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DW
Green
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK.
C J
CJ
Price
functional MRI; language; parietal lobe; phonological processing; speech production