To explore the neurophysiological and electroencephalography (EEG) changes that one single session of tDCS and robotics has in the SCI population (Study 1); and to investigate upper limb motor recovery in chronic tetraplegia SCI patients, comparing two rehabilitation strategies: real or sham tDCS combined with upper-limb robotic therapy (Study 2), as well as to characterize the neurophysiological (TMS) and brain signaling (EEG) profile of patients and specific muscles that respond to the combination of neuromodulation and robotic motor training.

Current training interventions for rehabilitating patients with SCI are designed to provide the greatest possible restoration of function in the shortest possible time. One of the major deficits in our current approach to applying therapy is that we have little ability to predict which patients are most likely to respond to therapy or which muscle groups are most amenable to improvement. Transcranial magnetic stimulation (TMS) is a noninvasive method to excite or inhibit neurons in the brain or the spinal cord. Numerous studies have been using this technique to map connections from the motor cortex via the spinal cord to peripheral muscles; and as a therapeutic tool to promote useful plasticity.

The significance of the present study lies in the potential of intensive upper limb motor training with a novel robotic device, in conjunction with transcranial direct current stimulation (tDCS) over the contralateral motor cortex, may enhance neural recovery and upper limb function in patients with tetraplegia.

The robotic training devices represent the most sophisticated interactive rehabilitation systems available on the current market; they are additionally appealing for their ability to quantify various aspects of movement, and they appear to be particularly powerful way to promote functional recovery. Furthermore, robotic devices can be used in collection of quantitative data from the patients, which can be interpreted to analyze their rate of progress. Rehabilitation robots are capable of providing important components of motor skill learning and muscle training: individually prescribed intensity, repetition, and performance feedback. Furthermore, they are a novel and reliable method of assessing voluntary motor control. Our center has extensive experience in the use of rehabilitation robotics in the assessment and training of voluntary motor control in SCI patients, as well as other neurological disorders. From the investigator's previous experience using robotic therapy in SCI patients they can predict that some patients (approximately 10%) will show direct benefits from the interactive robot training.

The use of neuromodulatory techniques (TMS, tDCS) has been used for the last 2 decades in neurorehabilitation with the aim of enhance motor recovery when paired with activity dependent plasticity (training). In this proposal the investigator's will be using a new tDCS device, StarStim® - a wireless multichannel device that allows EEG recording as well as real or sham tDCS stimulation.

The purpose of this study is: To explore the neurophysiological and electroencephalography (EEG) changes that one single session of tDCS and robotics has in the SCI population (Study 1); and to investigate upper limb motor recovery in chronic tetraplegia SCI patients, comparing two rehabilitation strategies: real or sham tDCS combined with upper-limb robotic therapy (Study 2), as well as to characterize the neurophysiological (TMS) and brain signaling (EEG) profile of patients and specific muscles that respond to the combination of neuromodulation and robotic motor training.

Study 1, Objective: To evaluate changes in cortical neurophysiological and biological brain signaling after a single session of tDCS. The TMS responses of the upper limb muscles with lack of voluntary motor control will be assessed prior and after 20 min of tDCS intervention. Additionally, the investigators will record EEG activity before, during and after the intervention.

Study 2, Objective: To explore the accumulative effects of 2 weeks of tDCS + Robotic training in cortical excitability and brain signaling. In addition, the investigators will investigate whether the intensive robotic training in conjunction with tDCS over the contralateral motor cortex area will enhance neural recovery and upper limb function in patients with tetraplegia.

The investigators will compare two different brain stimulation protocols to assess the enhancement of the motor performance of those muscles that lack motor control, comparing the effects of 2-weeks intensive hand-robotic training with real or sham tDCS.

The investigators hypothesize that the patients who undergo real tDCS in conjunction with prolonged intense robotic training will achieve greater improvements in motor function and sensation compared to their counterparts who are in the sham control group.

Inclusion Criteria:

• Level of injury C5 to T1
• Chronic SCI > 6 months
• Tetraplegic with some degree of motor dysfunction in the upper limb
• Motor Incomplete/Complete
• Medically stable

Exclusion Criteria:

• < 6 month after injury
• History of head trauma and/or cognitive deficit
• History of stroke, seizures or other intracranial disease
• Medically unstable
• Concomitant neurological disorder
• Pre-existing medical conditions interfering with unrestricted movement of the hand/arm (e.g. osteoarthritis, injury to the joints)
• Inability to provide informed consent
• Contraindications for non-invasive brain stimulation (NIBS) techniques (TMS & tDCS)- see below.

Non-Invasive Brain Stimulation Contraindications

• Surgically implanted foreign bodies such as a pacemaker, implanted medication pump, metal plate in the skull
• Metal inside the skull (other than dental appliances or fillings) that may pose a physical hazard during magnetic stimulation.
• No skin condition
• Any significant medical or psychiatric illness
• History of epilepsy

There is no plan to make individual participant data available to other researchers at this time.