J Med Assoc Thai 2018; 101 (11):1501-7

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Experience of Functional MRI Protocol in King Chulalongkorn Memorial Hospital [KCMH] for Thai Language Lateralization
Chosakun P Mail, Chaitusaney T , Rakvongthai Y , Lerdlum S

Objective: To investigate the effects of statistical thresholding and to determine an optimal functional magnetic resonance imaging [fMRI] statistical threshold for Thai language lateralization.

Materials and Methods: The present study was prospective descriptive study of twenty Thai native speaker right-handed healthy volunteers performed Thai verb and word generation paradigms during 3T fMRI. Bihemispheric activation difference of language region of interests was calculated for laterality index [LI] through ranks of statistical threshold, from the threshold that generated an empty map to the minimal threshold with p-value less than 0.05.

Results: LI of both verb generation and word generation paradigms tended to rise in higher statistical thresholds. In two subjects, shifted of LI from co-dominant to left dominant were found as an effect of statistical thresholding on both paradigms. A threshold (t-value) of 7 in verb generation paradigm and a threshold (t-value) of 6 in word generation paradigm significantly increased mean LI (with p-value 0.004 and 0.003, respectively) and categorized 95% of the subjects as left hemispheric dominance.

Conclusion: LI varies across different statistical thresholds. Optimal thresholds (t-value) for language lateralization are 7 in Thai verb generation and 6 in Thai word generation paradigms.

Keywords: Functional MRI, fMRI, Statistics, Threshold, Language lateralization, LI, Dominant hemisphere, Right-handedness, Thai


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