Primary sensory and motor cortex activities during voluntary and passive ankle mobilisation by the SHADE ortosis.

This study investigates cortical involvement during ankle passive mobilization in healthy subjects, and is part of a pilot study on stroke patient rehabilitation. Magnetoencephalographic signals from the primary sensorimotor areas devoted to the lower limb were collected together with simultaneous electromyographic activities from tibialis anterior (TA). This was done bilaterally, on seven healthy subjects (aged 29 ± 7), during rest, left and right passive ankle dorsiflexion (imparted through the SHADE orthosis, O-PM, or neuromuscular electrical stimulation, NMES-PM), and during active isometric contraction (IC-AM). The effects of focussing attention on ankle passive movements were considered. Primary sensory (FSS1) and motor (FSM1) area activities were discriminated by the Functional Source Separation algorithm. Only contralateral FSS1 was recruited by common peroneal nerve stimulation and only contralateral FSM1 displayed coherence with TA muscular activity. FSM1 showed higher power of gamma rhythms (33-90 Hz) than FSS1. Both sources displayed higher beta (14-32 Hz) and gamma powers in the left than in the right hemisphere. Both sources displayed a bilateral reduction of beta power during IC-AM with respect to rest. Only FSS1 beta band power reduced during O-PM. No beta band modulation was observed of either source during NMES-PM. Mutual FSS1-FSM1 coherence in gamma2 band (61-90 Hz) showed a slight trend towards an increase when focussing attention during O-PM. Somatosensory and motor counterparts of lower limb cortical representations were discriminated in both hemispheres. SHADE was effective in generating repeatable dorsiflexion and inducing primary sensory involvement similarly to voluntary movement.