The usefulness of a Brain Computer Interface for rehabilitation after stroke.

Each participant will receive a single session of the BCI-PAS intervention, and a single session of a Control intervention, on different days, 7 days apart (in a randomised order). Participants will be blinded to this order. During a baseline testing session, electroencephalography (EEG) will be recorded using an electrode cap, while subjects perform active ankle dorsiflexion of their affected leg, in time with a visual cue. The EEG is then analysed and the peak negativity of the movement related cortical potential (MRCP) is determined. This timing is then used to inform the timing of the BCI-PAS intervention. The BCI-PAS intervention will be delivered by a trained Research Assistant. During the BCI-PAS intervention, the subject will complete 50 repetitions of cued active ankle dorsiflexion of the affected leg. During each repetition of ankle dorsiflexion, a single pulse of electrical stimulation (pulse width 1ms) will be delivered to the deep branch of the common peroneal nerve (via two surface electrodes placed approximately 2-5cm anterior and inferior to the head of the fibula). The intensity of the electrical stimulation will be set to the level required to produce a palpable twitch in the tibialis anterior tendon. Each pulse of electrical stimulation will be timed to arrive in the motor cortex at the point of peak negativity of the MRCP. The BCI-PAS intervention takes approximately 15 minutes, with additional time required for setting up the electrical stimulation.