International audienceBrain-computer interfaces (BCIs) have been largely developed to allow communication, control, and neurofeed-back in human beings. Despite their great potential, BCIs perform inconsistently across individuals and the neuralprocesses that enable humans to achieve good control remain poorly understood. To address this question, weperformed simultaneous high-density electroencephalographic (EEG) and magnetoencephalographic (MEG) re-cordings in a motor imagery-based BCI training involving a group of healthy subjects. After reconstructing thesignals at the cortical level, we showed that the reinforcement of motor-related activity during the BCI skillacquisition is paralleled by a progressive disconnection of associative area...