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Speech apraxia without oral apraxia: can normal brain function explain the physiopathology?
Leonardo Bonilha1, Dana Moser, Chris Rorden
1Department of Communication Sciences and Disorders, University of South Carolina, Columbia, South Carolina 29209, USA.
Neuroreport
|June 23, 2006
Summary
Apraxia of speech, a motor disorder, is linked to brain damage. This study suggests the left inferior frontal gyrus, not the insula, is crucial for speech articulation.
Area of Science:
- Neuroscience
- Neurology
- Speech Science
Background:
- Apraxia of speech (AOS) is a motor speech disorder often resulting from stroke, characterized by impaired speech motor planning/programming.
- The precise neural correlates of AOS remain debated, with conflicting evidence implicating the insula and/or the inferior frontal gyrus (IFG).
- Co-existing lesions in both the insula and IFG in patient studies complicate the localization of speech articulation deficits.
Purpose of the Study:
- To investigate the distinct neural activation patterns for speech versus non-speech oral movements.
- To clarify the role of the insula and the left inferior frontal gyrus in speech articulation.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was employed in healthy individuals.
- Participants performed tasks involving speech movements and non-speech oral movements.
- Brain activation patterns were analyzed and compared between the two conditions.
Main Results:
- Speech movements selectively activated the left inferior frontal gyrus (Broca's area).
- The insula was not significantly recruited during speech articulation tasks.
- Non-speech oral movements showed different activation patterns than speech movements.
Conclusions:
- The findings suggest that the left inferior frontal gyrus, specifically Broca's area, plays a critical role in speech articulation.
- The insula does not appear to be essential for the motor planning of speech.
- This study provides evidence to resolve the controversy regarding the neural basis of apraxia of speech.
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