Motor imagery (MI) modifies the neural activity within the primary sensorimotor areas of the cortex in a similar way to a real movement. More precisely, beta oscillations (18-­‐25 Hz), which are often considered as a sensorimotor rhythm , show that the amplitude of brain oscillations is modulated before , during and after a MI. In most MI-based BCI experimental paradigm, subjects realize continuous MI, i.e a prolonged intention of movement, during a time window of a few seconds with the objective to increase the detection of ERD and ERS. However, when the subjects imagine a succession of movements, several ERD and ERS are generated, with lower amplitudes than those elicited by a single MI. Here, we employ a simple short MI to detect the ERD and the ERS.