[Voluntary synchronization and desynchronization of alpha rhythm by retroaction of EEG rhythms. Preliminary study (author's transl)].

Research was carried out on twenty subjects on the volontary control of alpha rythm by retroaction. Retroaction was provided in real time as a sound indicating the presence of alpha bursts or the intervals between bursts when reaching a pre-selected amplitude threshold, in such a way as to ensure that the alpha Index of the control situation (LB) reached about 50% of its total length. There are five situations per session: the initial state or base line (LB), relaxation with eyes closed (DF) and eyes open (DO), concentration with eyes closed (CF)and eyes open (CO), each situation being subdivided into 4 one-minute sequences. Subjects are informed about the alpha Index achieved at the end of each sequence, thus creating a periodic reinforcement. From the outset, three subjects showed an evident ability to increase or decrease at will the alpha occurrence rate, which gradually improved as the sequences progressed. Three other subjects showed that the same ability but to a lesser extent. Subjects confirmed that the feedback signal helped them to determine the most effective strategy for voluntary control, thus indicating that training is possible and that it is greatly facilitated by feedback, at least in the early stages. A detailed analysis of the recordings has made it possible for us to formulate hypotheses about the most important aspects of this control.