The objective of this research is to evaluate the efficacy of an experimental therapy for motor recovery of the arm after a stroke, which includes the application of a functional electrical stimulation therapy coupled to P-300 based Brain-Computer Interface system (BCI-FES). For this purpose, the investigators will compare two groups, the first one will receive only conventional physical therapy, while the second one will receive physical conventional therapy together with BCI-FES therapy. The control and experimental group will receive 20 sessions of conventional physical therapy at a rate of five sessions per week for 4 weeks, and the experimental group will receive 20 sessions of rehabilitation with the BCI-FES system at a rate of five sessions per week for 4 weeks. Broadly speaking, the BCI is in charge of determining the movement selected by the individual and assist the hand movement while performing functional tasks. The movements included in the sessions will be hand opening, grasping, pinching, pronation and supination, which are combined to facilitate the execution of functional movements that are performed together with the manipulation of daily used utensils. The visual, sensory and motor feedback provided by the BCI-FES system that enables the individual to replicate the afferent-efferent motor circuit, contributes to the activation and recruitment of neural pathways, which is associated with motor recovery. It should be noted that this BCI-FES system has already been tested previously in a study with healthy individuals, and in a non-randomized pilot study that used this therapy for upper limb motor function recovery in chronic post-stroke patients. It showed positive results, and the therapy was safe and tolerated by all the patients. Besides no adverse event related to the intervention occurred. To evaluate the results, a series of tests will be applied to assess the motor recovery and level of independence, including the FMA-UE: Fugl-Meyer Assessment Scale of Upper Extremity, ARAT: Action Research Arm Test, MAS: Modified Ashworth Scale, FIM: Functional Independence Measure and MAL: Motor Activity Log. Moreover, to assess neuroplasticity, two neuroimaging techniques including magnetic resonance imaging and electroencephalography will be used.