Manual Praxis, Language, Handedness, and Their Links to White Matter Structure

Justine Chen, BA

Brigham and Women’s Hospital,Massachusetts General Hospital – Research Assistant

Scientific Abstract

Background: Early work suggested a strong association between praxis, language, and handedness, with praxis and languages being lateralized to the left hemisphere in the brain. We examined 118 healthy individuals who were right, left, or mixed-handed. Based on functional imaging, the individuals were further categorized as having a) typical (left-lateralized) or not typical (not left-lateralized) language function, and b) typical (left-lateralized) or not typical (not left-lateralized) praxis. We tested how handedness, language, and praxis lateralization relate to white matter (WM).

Methods: We processed T1-weighted and diffusion-weighted images using motion, eddy correction, and masking. We determined fractional anisotropy (FA) for WM tracts related to praxis and language with WM Query Language: bilateral arcuate fasciculus, bilateral superior longitudinal fasciculus II and III, and corpus callosum (CC rostrum, CC genu). We applied three MANCOVAs with eight dependent variables (FA values of all tracts), sex as a covariate, handedness, language-lateralization, and praxis as the independent variable, respectively. We then calculated post-hoc ANCOVAs again, correcting for sex effects.  

Results: Forty-six individuals were right, 38 were left, and 34 were mixed-handed. Language lateralization was typical in 103 and atypical in 15 individuals. Praxis lateralization was typical in 83 and atypical in 35 individuals. MANCOVAs did not demonstrate a significant effect of language (F(8,108)=.93, p=.50) nor handedness (F(16, 216) = 1.30, p=.20) on WM. Post-hoc analyses showed a significant handedness effect for left AF (p=.018) and CC genu (p=.033), with right-handed individuals displaying lower FA values than left or mixed-handed individuals.

Conclusion: Contrary to functional findings, we did not observe any effect of language on WM and only a regional effect of handedness. Future research should include lateralization and network analyses to truly understand the complex interplay between language, praxis, handedness, and brain structure.

Live Zoom Session – March 9th

research Areas


Justine Chen, BA, Johanna Seitz-Holland, MD, PhD, Nikos Makris, MD, PhD, Marek Kubicki, MD, PhD, Mikolaj Pawlak, MD, PhD, Krzystof Szwed, MD, PhD, Gregory Kroliczak, PhD

Principal Investigator

Marek Kubicki, MD, PhD

Affiliated Website