Sensorimotor rhythm neurofeedback protocol consisted of 20 individual sessions, twice a week, during 11 weeks maximum. For each subject MCI, NF was planned and conducted by a neuropsychologist experienced in neurophysiology and neurofeedback. Each session lasted 1h10-15min and was conducted as follows:

1. Preparation and installation of the electrodes, verification of the impedance, adjustment of the calibration and thresholds (15 minutes).
2. NF training (tasks and video described below) (45 minutes).
3. Feedback and debriefing about the session (15 minutes).

SMR neurofeedback training consisted to increase the synaptic strengths and sensitivity within this network. Electroencephalography signals for SMR/theta ratio training was recorded at channel Cz according to the International 10-20 system. Theta rhythm was also recorded and, in this case, SMR was stimulated while theta waves were suppressed. A 32 channels system (EEGDigitrack Biofeedback plus module, Inc Elmiko Medical) was used for SMR/theta neurofeedback training.

Neurofeedback Technology Acceptation Questionnaire assessed the participants' opinions face to the electroencephalography neurofeedback intervention with 33 questions. The mode of administration was a personal interview with the investigator, the type of questions was closed-ended (for binary variable yes or no). Answers were analyzed with the Multiple Correspondence Analysis to visualize associations and similarities among participants and answers to Questionnaire. An unsupervised hierarchical clustering was performed using the Euclidean distance and Ward's method. Clusters were defined graphically using dendrogram.