Not to be a Debbie Downer, but I seriously question how much actual alpha wave activation they're getting if they're just measuring it from the frontal electrodes (Fp1/2 and G). Chances are they're just measuring muscle activity from the person wrinkling their forehead.
The more reliable method would be to look at mu inhibition, since you'd actually be able to measure things other than muscle movements.
Right, very good point. We did notice eye movement and blinking artifacts showing up as well, and we were initially skeptical for these very same reasons.
We also implemented an alternative control scheme using mu suppression which we tried measuring using C3, C4, and Cz. This worked by having the user imagine (or actually move) their hands or feet to control the paddle movement. The other thing was that we actually used back of the head (mastoid) and right ear lobe instead of G.
The last thing I'd like to mention is that frontal alpha measurement is all over the research literature -- commercial products exist that use headbands to measure alpha activity. We noticed increases in alpha wave spectral power when the subject was relaxing or meditating -- precisely when the subject would least likely be scrunching their forehead. This was noticed even in neurofeedback applications when the subjects were not playing the game.
