This study aims at comparing the effects of transcranial direct current stimulation and transcranial pulsed current stimulation on neurophysiological outcomes on patients with disorders of consciousness. This study also aims to evaluate the effects of these techniques on patients' level of consciousness.

Inclusion Criteria:

• Fluent in English or French
• Legally authorized surrogate available to provide informed consent
• History of non-traumatic brain injury with loss of consciousness caused by stroke, cerebral hemorrhage, hypoxic ischemic insult, metabolic disorder or infection.
• Has been followed clinically on the CRS-R for a minimum two weeks and has undergone a minimum of 4 assessments with the CRS-R.
• Serial CRS-R scores show at least one subscale on which there is no behavioral sign of conscious awareness (ie, command following, visual fixation or pursuit, object localization or recognition, localization to noxious stimulation, object manipulation, automatic motor responses, functional object use, discernable speech, discernable yes no communication, based on clinically obtained scores contained in the medical record).
• CRS-R screening examination completed by research staff confirms the absence of a behavioral sign of consciousness on a least one CRS-R subscale.
• Medically stable (i.e., no systemic illness or disease) and capable of independent ventilation

Exclusion Criteria:

• History of developmental, neurologic, or major psychiatric disorder resulting in functional disability up to time of enrollment.
• Evidence or surrogate report of uncontrolled seizure disorder
• Metallic brain implant or implanted electronic brain medical devices or pacemaker
• Subjects with craniectomy
• History of cranioplasty in the frontal region or recent cranioplasty that has not yet fully healed
• Pregnancy