Technology Review: Blogs: Mims's Bits: How Close Is a Workable Brain-Computer Interface? About that asynchronicity: it turns out that, because of the bandwidth limitations of recording brain activity through EEGs -- external electrodes placed on the outside of the head -- previous attempts at noninvasive brain computer interfaces required that users only direct the computer during certain time slots. Imagine a metronome ticking very slowly, say once a second, directing you to imagine the movement of your robotic arm starting... now. How tedious.
Iáñez and colleagues' approach gets around this limitation by using four different models, each with assumptions that are sometimes the opposite others. This way, however a subject's brain happens to be wired up, all the computer has to figure out is whether they mean "left" or "right" in order to direct a robot arm in two dimensions.