I’m not sure I believe this is truly the first in brain-machine interfaces in Japan; after all, we’ve had them in the US for years (I even wrote a paper on them a few years ago). The idea is that an array of microelectrodes attached directly to the surface of the brain gives a more accurate and precise representation of local brain activity, which can allow for better control of, say, prosthetic limbs.
The theory is sound, but the problem is it requires open-skull surgery, which makes finding volunteers kind of difficult. The difficulty is offset by the fundamental coolness of taking part in cybernetics research, which just sounds awesome. I was part of an experiment involving the alternative method, scalp conductance, and that was messy enough. Took forever to get the insulating gel out of my hair.