Study of Hemodynamic Markers of Upper Extremity Motor Dysfunction in Stroke Patients Using Functional Near Infrared Spectroscopy (fNIRS)

For Healthy Volunteers: Inclusion Criteria: 1\. Availability of signed written informed consent. 3. Absence of somatic and psychiatric diseases (more details in the exclusion criteria) 4. Ability and willingness to comply with the requirements of this protocol. Exclusion Criteria: 1. The presence of superficial injury of head (S00-S09 International Classification of Diseases 10 (ICD-10). 2. The presence of mental, behavioural disorders (F00-F99 ICD-10). 3. Drug addiction in the past or at the moment. 4. The presence of diseases of the nervous system (G00-G99 ICD-10). 5. . History of intracranial injury (S06 ICD-10) or stroke (I64 ICD-10). 6. The presence of somatoform disorders (F45 ICD-10). 7. Any conditions that, in the opinion of the Investigator, meet the exclusion criteria 8. Presence of electrical and/or metallic implants or stimulants in the body (eg, implanted deep brain stimulation devices, pacemakers, hearing aids and cochlear implants, intracranial metal implants). 9. Pregnancy 10. The presence of malignant neoplasms (C00-C97 ICD-10). For stroke patients: Inclusion Criteria: 1. Signed written informed consent. 2. People after the first acute cerebrovascular accident (CVA), early or late rehabilitation period. 3. The level of severity of paresis of the upper limb from 3 points to 0 (according to a 6-point neurological scale) 4. The minimum visual acuity is not lower than 0.2 on the Sivtsev scale. 5. The ability and willingness of the patient to comply with the requirements of this protocol. 6. Expressed patient motivation for rehabilitation. Exclusion Criteria: 1. Severe cognitive impairment (\<10 points according to the Montreal Cognitive Assessment Scale). 2. Hamilton score above 18 points. 3. The score on the Rankin scale is above 4 points. 4. Associated neurological disorders that cause decreased muscle strength or increased muscle tone in the upper limbs (eg, cerebral palsy, brain damage from trauma) or stiffness (eg, Parkinson's disease, contracture). 5. Late stages of arthritis or clinically significant limitation of passive range of motion in any of the joints studied in the study due to other reasons. 6. The absence of a part of the upper limb due to amputation caused by various reasons. 7. Any medical condition, including mental illness or epilepsy, that may affect the interpretation of study results, study conduct, or patient safety. 8. Alcohol abuse, medical marijuana use, or recreational drug use in the 12 months prior to Visit 1. 9. Use of experimental drugs or medical devices within 30 days prior to Visit 1. 10. Lack of ability to follow study procedures, in the opinion of the investigator. 11. The severity of the patient's condition according to the neurological or somatic status, which does not allow full rehabilitation. 12. Severe visual disturbances, minimal visual acuity less than 0.2 Sivtsev visual acuity table. 13. Unstable angina and/or heart attack within the previous month 14. Repeated stroke. 15. Severe unilateral spatial neglect. 16. Uncontrolled arterial hypertension 17. Ataxia 18. All forms of epilepsy