Non-invasive brain-spine interface: continuous brain control of trans-spinal magnetic stimulation using EEG

Brain-controlled neuromodulation therapies have emerged as a promising tool to promote functional recovery in patients with motor disabilities. This neuromodulatory strategy is exploited by brain-machine interfaces and could be used for restoring lower limb muscle activity or alleviating gait deficits. Towards a non-invasive approach for leg neurorehabilitation, we present a set-up that combines acquisition of electroencephalographic (EEG) activity to volitionally control trans-spinal magnetic stimulation (ts-MS). We engineered, for the first time, a non-invasive brain-spine interface (BSI) to contingently connect motor cortical activation during leg motor imagery with the activation of leg muscles via ts-MS. This novel brain-controlled stimulation was validated with 10 healthy participants who underwent one session including different ts-MS conditions. After a short screening of their cortical activation during lower limb motor imagery, the participants used the closed-loop system at different stimulation intensities and scored system usability and comfort. We demonstrate the efficiency and robustness of the developed system to remove online stimulation artifacts from EEG regardless of ts-MS intensity used. All the participants reported absence of pain due to ts-MS and good usability. Our results also revealed that ts-MS controlled afferent and efferent intensity-dependent modulation of the nervous system. The here presented system represents a novel non-invasive means to neuromodulate peripheral nerve activity of lower limb using brain-controlled spinal stimulation.