Spinal cord injury (SCI) is a highly debilitating pathology, associated with the loss of sensorimotor functions, autonomy and quality of life. Although there is currently no cure, brain-machine interfaces (BMI) have been used as a method of SCI rehabilitation. BMIs use neurophysiological signals recorded by techniques such as electroencephalography (EEG) to produce a response in a device. Recently, BMIs have achieved clinically relevant improvements in several neuropathologies. However, the biological basis of these therapeutic protocols is yet to be studied, which is extremely important to improve their effectiveness.

Therefore, in this study it is applyed an improved BMI protocol by combination with virtual reality (VR), sensory feedback (visual, auditory, and tactile), and/or exoskeleton to characterize in detail the dynamics of information transfer between the various participants' brain regions (primary objective of the overall study, which involves participants with and without SCI), and improve the rehabilitation of SCI patients. For this, the neurophysiological signals obtained by EEG will be studied, with particular interest in the altered activity that correlates with relevant clinical improvements in the rehabilitation of SCI patients.

At the beginning of the study, the following data will be collected from the participant: age, gender; specifically for participants with SCI, data associated with the injury will also be collected; level and type of injury, time post-injury, functional classification, neurological manifestations, e.g. neuropathic pain.

During the study, the participant will be monitored weekly in a total of 12 sessions, each with an expected duration of one to two hours. In these sessions, the participant will perform a 'BMI protocol': they will move a virtual avatar using motor imagery (thinking about movement) in VR, with sensory feedback provided by VR equipment and tactile sleeves. Participants without SCI will also be able to wear an exoskeleton (ExoAtlet). The VR software was developed by the research group and is locally installed on a computer for exclusive use for the implementation of this BMI protocol. It is important to note that the software operates without a network connection and does not collect any type of personal data. The participants' brain activity will be recorded by the non-invasive EEG technique, while the participant is performing the BMI protocol, in which they will have to perform mental tasks such as walking and resting. Each session has three blocks: a first one for the participant's familiarization with the virtual scenario and/or exoskeleton; and the rest to train and carry out the tasks.

At the end, questionnaires will be carried out to assess comfort or possible undesirable effects during the VR experience (e.g., fatigue or nausea) and the participant will be given the opportunity to report their experience during the session. The EEG data from subsequent sessions will be analyzed and compared over time to identify changes in the participants' brain activity promoted by this rehabilitation protocol. Blood samples will also be collected at the beginning and end of the study (1st and 12th session), to evaluate molecules potentially associated with rehabilitation. These samples, anonymized at the end of their participation in this study, will be preserved in the Institute of Biomedicine (iBiMED, University of Aveiro) Biobank for 20 years, under the responsibility of the principal investigators, to be used in the present study. Their samples and anonymized data may be used in other future studies of the same scope, but such use will always require consent from the responsible ethics committee.

Participants with SCI will be asked about the evolution of neuropathic pain (if any) with different pain scales. At the beginning and end of the study (1st and 12th session), the standard neurological and functional classification of the lesion will be performed by physicians/therapists, according to the rehabilitation center's routine. Three months after being discharged from the center, during the revisit consultation, the clinical data described here will be collected again.