In previous studies, the cortical lateralization was observed for hemispheric dominance investigation via the laterality index (LI) [40–43]. For fNIRS measurement, the LI indicates the quantification of left and right hemispheres contributions of oxygenation dynamic response [41, 44]. We can define the LI as:LI=TL−TRTL+TR(2)where TL is the mean concentration of ΔtHb of a given left channel of PFC in resting-state; TR is the mean concentration of ΔtHb of a given right channel of PFC in resting-state. Accordingly, a positive value of LI indicates leftward dominance, and a negative value of LI indicates rightward dominance. A near-zero value of LI indicates bilateral dominance that depends on statistical analysis. A two-tailed t-test was performed to determine if LI is a near-zero value or not. Then the one-tailed t-test was performed to determine the leftward or rightward dominance.
