I don't really understand why this is so significant or perhaps I don't understand the experiment. You are fed some training set and a certain brain activity pattern is identified as the "target." Then you show a whole bunch of other stimuli and try to teach the brain to display the target activity pattern for a different stimulus by having this proxy indicator that tells you how close you are (green disk).

Don't we do this all the time? If I'm teaching a child the letters of the alphabet then I would show an example, have them try to guess it and then give them some indication of how close they are (yes you got it, you are pronouncing it weird, no that's the wrong letter). The only difference here is that you are using proxy whereby you identify a target brain activity pattern first. It seems pretty much impossible, however, to get a target for an individual without first seeing what the target is. Certainly everyone's "target" for the same problem must look quite different.

I suppose this could be pretty useful for brain-computer interfaces but I don't know if I'd go as far as saying this is matrix-like learning.