Reproducibility of corticokinematic coherence for proprioceptive stimulation of the ankle joint

Corticokinematic coherence (CKC) between cortical oscillations and limb kinematics reflects the cortical processing of proprioceptive afference. However, it remains unknown whether CKC to lower-limb proprioceptive stimulation is reproducible. Here we examined the reproducibility of CKC for the ankle joint in ∼one-year follow-up study. Twenty-seven healthy volunteers participated in two magnetoencephalography (MEG) sessions separated by 13.2 ± 1.4 months. Continuous passive ankle-joint rotations were elicited at 2 Hz (4 min for each ankle) using MEG-compatible pneumatic actuators. Coherence was computed between foot acceleration and MEG signals. CKC strength was defined as the strongest coherence value from the vertex gradiometer pair above the foot region of the primary sensorimotor (SM1) cortex. CKC strength did not differ significantly between sessions for the left (Session 1: 0.36 ± 0.14 vs. Session 2: 0.39 ± 0.15) or right (0.31 ± 0.15 vs. 0.32 ± 0.14) ankle, nor between ankles. Intraclass correlation coefficient (ICC) values indicated moderate day-to-day CKC reproducibility for both left (0.65) and right (0.67) ankle at 2 Hz, but good reproducibility for the left ankle (0.79) and moderate for the right ankle (0.66) at 4 Hz. However, a high degree of inter-individual variability in CKC strength was observed, and some individuals showed considerable inter-session variability. CKC in response to proprioceptive stimulation of the ankle joint is reproducible at the group level. Our results support the applicability of CKC in longitudinal studies to examine cortical processing of lower-limb proprioceptive afference, but caution should be considered when following or comparing single individuals.