Training protocol evaluation of a brain-computer interface:: Mental tasks proposal

Introduction. A brain-computer interface (BCI) is based on the analysis of the electroencephalographic (EEG) signals recorded during certain mental activities, to control an external device. Main users are people with severe neuro-muscular disorders, like amyotrophic lateral sclerosis. One of the most important problems to control a BCI is the need of providing suitable training, helping subjects to get some control EEG signals. Aim. To carry out a study of possible effects of use of specific mental tasks during the first phase of the training period. Subjects and methods. Eighteen healthy untrained subjects took part in the experiment. A group of subjects were trained to discriminate between two motor imagery tasks (imagination of right and left hand movements). Another group were trained to discriminate between a motor imagery task (imagination of right hand movements) and mental relaxation. Objective and subjective measures based on questionnaires were taken. Results. Some subjects do not achieved EEG control, but subjects at the second group showed a greater facility to control a BCI. Conclusion. Training protocols should not be randomly chosen; they must be adopted to the subject to be effective. Sometimes it is necessary to increase the number of sessions without feedback before submitting a subject to a session with feedback and a correct choice of the mental tasks is very important. Mental tasks which are easy to discriminate improve classification result and produce better satisfaction to the subject.