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Transcranial Direct Current Stimulation (tDCS) of Wernicke's and Broca's Areas in Studies of Language Learning and Word Acquisition
Published on: July 13, 2019
Neural networks essential for naming and word comprehension
Melissa Newhart1, Lynda Ken, Jonathan T Kleinman
1Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Baltimore, MD, USA.
Summary
Aphasia research often links single brain areas to language deficits. This study shows multiple perisylvian regions contribute to naming, spoken, and written word comprehension in stroke patients.
Area of Science:
- Neuroscience
- Neurolinguistics
- Cognitive Psychology
Background:
- Aphasia lesion studies traditionally implicate single brain regions in specific language deficits.
- Emerging evidence from functional imaging and lesion studies suggests a network-based approach is necessary for understanding language processing.
- The precise neural correlates of different language tasks remain incompletely understood.
Purpose of the Study:
- To investigate the relative contributions of multiple brain regions to basic language tasks in acute stroke patients.
- To determine if distinct or overlapping neural networks underlie naming, spoken word comprehension, and written word comprehension.
- To challenge the traditional single-lesion-deficit model of aphasia.
Main Methods:
- Recruited 156 patients with acute stroke.
- Administered basic language assessments: naming, spoken word comprehension, and written word comprehension.
- Utilized magnetic resonance imaging (MRI), including diffusion and perfusion imaging, to map brain lesions.
- Employed multivariate linear regression to associate lesion locations with language task performance.
Main Results:
- Error rates across all language tasks were best predicted by dysfunction in multiple perisylvian brain regions.
- Common perisylvian regions were implicated across naming, spoken, and written word comprehension tasks.
- Distinct perisylvian regions were uniquely associated with specific language tasks, highlighting task-specific neural substrates.
- Multivariate analysis demonstrated that a network of regions, rather than a single area, underlies language function.
Conclusions:
- Language functions like naming and comprehension are subserved by distributed neural networks within the perisylvian cortex.
- Both shared and unique brain regions contribute to different aspects of language processing in aphasia.
- These findings support a network model of aphasia, moving beyond single-region explanations.
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