motor imagery

Motor imagery is imagining a movement vividly without actually making it — picturing yourself squeezing your right hand, or wiggling your toes, while staying perfectly still. Remarkably, the brain regions that plan and command real movement light up during the imagined version too, almost as if a quiet rehearsal were running.

That rehearsal leaves a measurable trace: over the sensorimotor cortex, the idling mu and beta rhythms dip in power on the side that controls the imagined limb. A BCI can spot which limb you imagined from where that dip appears — left-hand imagery shows up over the right side of the brain, and vice versa.

What makes this paradigm special is that the control signal comes entirely from inside. There is no flickering screen or flashing grid to look at, so the user can drive a cursor, a wheelchair, or a robotic arm purely by intention — though it usually takes practice to produce a clear, steady signal.