Table 1.

Diffusion tractography normalized streamline counts and asymmetry indices (AIs) in chimpanzees and humans.

	Left dorsal	Right dorsal	Left ventral	Right ventral	Left D/V AI	Right D/V AI	Dorsal L/R AI	Ventral L/R AI
Human	116073	53214	27947	34753	0.61 ± 0.06**	0.00 ± 0.13	0.42 ± 0.11**	−0.17 ± 0.09
Chimpanzee	2865	379	23761	18942	−0.84 ± 0.08**	−0.88 ± 0.08**	0.66 ± 0.07**	0.08 ± 0.10
Human–Chimpanzee					1.44 ± 0.10**	0.89 ± 0.15**	−0.24 ± 0.13	−0.24 ± 0.13

Streamline counts were normalized to remove variance in ROI size (after deformation from standard ROIs to individuals) and for differences in trackability across subjects within a species. The assumption was made that the total number of streamlines counted across all four pathways should be the same across individuals within a species, as we are only interested in relative differences between the pathways across subjects and want the average normalized streamline counts to reflect equal contributions from all subjects. D, dorsal, V, ventral, L, Left, R, right, AI, Asymmetry Index [AI_LR = (W_L − W_R)/(W_L + W_R) or AI_DV = (W_D − W_V)/(W_D + W_V)], * = p < 0.05, ** = p < 0.01.