Implementation of clinically relevant and robust fMRI-based language lateralization: Choosing the laterality index...

Area of Science:

• Neuroimaging
• Neurosurgery
• Cognitive Neuroscience

Background:

• Language lateralization assessment is crucial for neurosurgery planning near eloquent brain areas.
• Functional magnetic resonance imaging (fMRI) provides quantitative language lateralization using a laterality index (LI).
• Conventional LI calculation methods are limited by threshold dependency.

Purpose of the Study:

• To introduce a simplified, threshold-independent method for calculating the laterality index (LI).
• To compare the proposed LI calculation method against three existing threshold-independent approaches.
• To evaluate LI calculation consistency across different methods and brain regions.

Main Methods:

• Fifteen healthy subjects performed language tasks (picture naming, verb generation, word fluency) during fMRI scanning.
• Laterality index (LI) values were computed using four distinct threshold-independent methods.
• Analyses considered both whole-hemisphere and atlas-defined language areas.
• Subject rankings based on LI values were compared across methods.

Main Results:

• All tested LI calculation methods demonstrated agreement in distinguishing strong from weak language lateralization (Spearman's correlation coefficients 0.59-1.00).
• Language-specific areas generally showed more pronounced lateralization compared to the whole hemisphere.
• The novel method proved simple, fast, and robust for clinical application.

Conclusions:

• The developed simplified LI calculation method is suitable for clinical use in presurgical planning.
• While method choice may not be critical, consistency in LI calculation is essential for comparative analysis.
• The findings support the utility of fMRI-based language lateralization assessment in neurosurgery.