Assessment of hemispheric language lateralization: a comparison between fMRI and fTCD

Area of Science:

• Neuroscience
• Medical Imaging
• Cognitive Science

Background:

• Assessing cerebral blood flow velocity (CBFV) during cognitive tasks is crucial for understanding brain function.
• Functional transcranial Doppler ultrasonography (fTCD) and functional magnetic resonance imaging (fMRI) are non-invasive techniques used to measure brain activity.
• The relationship between CBFV changes and regional cerebral blood flow (rCBF) during language processing requires further investigation.

Purpose of the Study:

• To investigate the relationship between event-related CBFV modulations in the middle cerebral artery (MCA) and rCBF changes during a word-generation task.
• To compare the language laterality index derived from fTCD (LIfTCD) with that derived from fMRI (LIfMRI).
• To determine if fTCD and fMRI can be used complementarily for language lateralization.

Main Methods:

• 13 healthy subjects underwent both fTCD and fMRI during a word-generation task.
• CBFV changes in the left and right MCA were measured using fTCD.
• Language-induced activation (number of voxels) in the left and right hemispheres was measured using fMRI.
• Language laterality indices were calculated for both fTCD (LIfTCD) and fMRI (LIfMRI).

Main Results:

• A close linear relationship was observed between LIfTCD and LIfMRI (r = 0.95, p < 0.0001).
• Language-related velocity changes in the MCAs were found to correlate linearly with rCBF increases.
• The results indicate strong agreement between the laterality indices obtained from both techniques.

Conclusions:

• fTCD and fMRI provide comparable measures of language lateralization.
• Language-related CBFV changes in the MCAs are linearly related to rCBF increases.
• fTCD and fMRI can be utilized in a complementary manner for the assessment of language processing in the brain.