Fig. 6: ROI analyses.

Violin plots showing that the average resting-state functional connectivity (rsFC) of the right-hand (Ml) motor seed in the left premotor ROI (6d_l; a) was lower and that of the left-hand (Mr) motor seed higher for left- (L, n = 600) compared to right- (R; n = 600) and mixed-handers (M; n = 600). Conversely, the average rsFC of the Ml seed in the fundus of the superior temporal visual area (FST; b) ROI was higher and that of the Mr seed lower for L than for R or M. Findings reproduced in the Discovery (n = 909) and Replication (n = 891) samples. Distribution of the laterality index (Eq. 2) for different groups and ROIs in the left (c) and right (d) hemispheres. The box extends from the lower to the upper quartile (25th to 75th percentile) of the data, with the horizontal line representing the median. The whiskers extend to 1.5 times the interquartile range from the lower and upper quartiles, and outliers beyond this range are represented as individual points. Statistical model: Two-sample T-test (2-sided). CER: cerebellum lobe V; 24dd: mid cingulum; POS2: parieto-occipital sulcus, area 2; IPS1: intraparietal sulcus area 1; Brodmann areas 1: somatosensory, 4: superior motor, 6d: premotor, and 40: inferior parietal. Error bars are standard errors of the means. Source data are provided as a Source Data file.