Desynchronization related to the motor attempt of patients with hemiplegia: case studies, with and without visual feedback

Stroke is the leading cause of paralysis in adults, who suffer major motor sequelae and usually need a rehabilitation therapy. For this purpose, brain computer interfaces (BCI) can be used, and one of its paradigms is the motor imagery. A number of electroencephalographic (EEG) studies have reported that the movement intention is evidenced as a power decrease of the sensory motor rhythm in the electroencephalographic signal, which is known as event related desynchronization (ERD). The goal of this paper was to study the EEG signals recorded from the intention of foot movement in two stroke survivors. This study consisted in two stages where the subject was asked to intent to move his affected foot. During the first stage, no visual feedback was given, but it was given in the second one. The spectrum, the topographic distribution and the features map of the coefficient of determination r2 were obtained and analyzed. Both subjects could achieve a localized desynchronization during the second stage whilst only one could during the no visual feedback stage. These results show that these subjects, despite of their lesion, could achieve high enough ERD levels to command a BCI, and that using a visual feedback for therapeutic purposes could benefit the patients to get it.