Note that this doesn’t work by detecting his “imagined” letters. It’s detecting him trying to move his paralyzed hand through the motion of drawing the letters

Note that this doesn’t work by detecting his “imagined” letters. It’s detecting him trying to move his paralyzed hand through the motion of drawing the letters on paper. By measuring the motor cortex activity it seems to be looking at something closer to an “output” of the brain rather than an internal representation. So detecting imagined letters or words or ideas seems like a different problem than this achievement.