Fig. 2. Functional connectivity and cortical thickness of the M1 inter-effector motif.

a, Brain regions with the strongest functional connectivity to the left middle inter-effector region (exemplar seed) in cortex, striatum, thalamus (horizontal slice; CM nucleus) and cerebellum (flat map) in the exemplar participant (P1). See Extended Data Fig. 3 for other participants. b, Left, brain regions more strongly functionally connected to inter-effectors than to any foot, hand or mouth regions (P1; Supplementary Fig. 2a for other participants). Purple outlines show the CON (individual-specific). Central sulcus is masked as it exhibits large differences by definition. Right, connectivity was calculated between every network and both the inter-effector and effector-specific M1 regions. The plot shows the smallest difference between inter-effector and any effector-specific connectivity, averaged across participants. This difference was larger for CON than for any other network (two-tailed paired t-tests, *P < 0.05, FDR-corrected; **P < 0.01, FDR-corrected). Coloured circles represent individual participants. c, Inter-network relationships visualized in network space using a spring-embedding plot, in which connected regions are pulled together and disconnected regions are pushed apart. Connecting lines indicate a functional connection (Z(r) > 0.2) (P1; see Supplementary Fig. 2b for all participants). d, Inter-effector and effector-specific regions were tested for systematic differences in the temporal ordering of their infra-slow fMRI signals³⁴ (<0.1 Hz). The plot shows signal ordering in CON, inter-effector and effector-specific regions, averaged across participants (standard error bars; two-tailed paired t-test *P < 0.05, uncorrected). Coloured circles represent individual participants. Prior electrophysiology work suggests that later infra-slow activity (here, CON) corresponds to earlier delta-band (0.5–4 Hz) activity³⁵. e, In each participant (filled circles), inter-effector regions exhibited lower cortical thickness than all effector-specific regions (two-tailed paired t-test **P ≤ 0.01, FDR-corrected). Attn., attention; mem., memory.