Injuries affecting the central nervous system may disrupt the cortical pathways to muscles causing loss of motor control. Nevertheless, the brain still exhibits sensorimotor rhythms (SMRs) during movement intents or motor imagery (MI), which is the mental rehearsal of the kinesthetics of a movement without actually performing it. Brain-computer interfaces (BCIs) can decode SMRs to control assistive devices and promote functional recovery. Despite rapid advancements in non-invasive BCI systems based on EEG, two persistent challenges remain: First, the instability of SMR patterns due to the non-stationarity of neural signals, which may significantly degrade BCI performance over days and hamper the effectiveness of BCI-based rehabilitation. Second, differentiating MI patterns corresponding to fine hand movements of the same limb is still difficult due to the low spatial resolution of EEG. To address the first challenge, subjects usually learn to elicit reliable SMR and improve BCI control through longitudinal training, so a fundamental question is how to accelerate subject training building upon the SMR neurophysiology. In this study, the investigators hypothesize that conditioning the brain with transcutaneous electrical spinal stimulation, which reportedly induces cortical inhibition, would constrain the neural dynamics and promote focal and strong SMR modulations in subsequent MI-based BCI training sessions - leading to accelerated BCI training. To address the second challenge, the investigators hypothesize that neuromuscular electrical stimulation (NMES) applied contingent to the voluntary activation of the primary motor cortex through MI can help differentiate patterns of activity associated with different hand movements of the same limb by consistently recruiting the separate neural pathways associated with each of the movements within a closed-loop BCI setup. The investigators study the neuroplastic changes associated with training with the two stimulation modalities.

Inclusion Criteria:

1. Able-bodied participants:

   • good general health
   • normal or corrected vision
   • no history of neurological/psychiatric disease
   • ability to read and understand English (Research Personnel do not speak Spanish)

2. Subjects with motor disabilities

   • motor deficits due to: unilateral and bilateral stroke / spinal cord injury / motor neuron diseases (i.e. amyotrophic lateral sclerosis, spino-cerebellar ataxia, multiple sclerosis) / muscular diseases (i.e. myopathy) / traumatic or neurological pain / movement disorders (i.e. cerebral palsy) / orthopedic / traumatic brain injury / brain tumors
   • normal or corrected vision
   • ability to read and understand English
   • ability to provide informed consent

Exclusion Criteria:

1. Subjects with motor disabilities

   • short attentional spans or cognitive deficits that prevent the subject from concentrating during the whole experimental session
   • heavy medication affecting the central nervous system (including vigilance)
   • concomitant serious illness (e.g., metabolic disorders)

2. All participants

   • factors hindering EEG/EMG acquisition and the delivery of non-invasive electrical stimulation (e.g., skin infection, wounds, dermatitis, metal implants under electrodes)
   • criteria identified in safety guidelines for MRI and TMS, in particular metallic implants

All data will be made available by the online publication date

Data will be placed in public servers for any interested researcher to access it