Investigation of Proprioceptive Responses to Passive Lower Limb Movements Based on Corticokinematic Coherence

Corticokinematic coherence (CKC) is the phase coupling between limb kinematics and cortical neurophysiological signals, reflecting cortical processing of proprioceptive afference. While previous CKC research has primarily focused on passive finger movements, cortical responses to passive lower limb movements remain insufficiently explored. This study developed a lower limb movement actuator to deliver rhythmic passive lower limb movements across a range of frequencies and amplitudes. Ten healthy participants were recruited to evaluate how stimulation parameters influence CKC, computed from coherence between electroencephalography (EEG) and limb acceleration (Acc) signals. Results indicated CKC strength increased with movement frequency at amplitudes of 100-160 mm. For larger amplitudes (180 mm, 200 mm), CKC strength reached maximum at 1.2 Hz and 1.0 Hz, respectively. At low frequencies (0.6-1.0 Hz), CKC increased monotonically with amplitude, whereas at higher frequencies (1.2-1.4 Hz), a non-monotonic relationship was observed, with peaks occurring at 180 mm and 160 mm. These findings suggest that moderate rhythmic stimulation can effectively enhance cortical proprioceptive responses. Optimal stimulation combinations were identified as 1.0 Hz with 160 mm, 1.2 Hz with 140-180 mm, and 1.4 Hz with 100-180 mm. These findings contribute to a better understanding of how stimulation parameters influence cortical proprioceptive responses and may lay the foundation for developing future rehabilitation strategies.