Stable and Independent Communication Brain-computer Interfaces

Inclusion criteria for healthy persons: * Older than 18 * Fluent in French, English, German or Italian * Good visual acuity Inclusion criteria for people with tetraplegia: * Older than 18 * Fluent in French, English, German or Italian * Good visual acuity * Diagnosed with spinal cord injury, brainstem stroke, spinal stroke, muscular dystrophy or other non-degenerative motor neuron disorders * Limited or no ability to use both hands - less than grade 4 muscle strength in elbow extension and wrist extension and less than grade 2 strength in finger flexor and abduction on both sides Inclusion criteria for people with locked-in syndrome: * Were fluent in French, English, German or Italian before losing the ability to speak * Enough visual capability to see large letters from a distance of around 50cm according to caretaker's or guardian's opinion Exclusion criteria for healthy persons: * Smokers * Substance or alcohol abuse * Neurological or psychiatric illness * History of cranio-facial surgery * Metallic implants that would prohibit the subject from having a MRI scan * Medications that may retard motor coordination and cognitive ability (such as sedatives) * Seizure disorders * Treated with anti-epileptic medications Exclusion criteria for people with tetraplegia and locked-in syndrome: * Disabling neurological illness other than tetraplegia or locked-in syndrome * Disabling psychiatric illness * History of cranio-facial surgery