Intuitively (I did some research in bioinformatics, including the brain, but mostly its genetics) I would think ADHD could quite possible respond to something like this, while for autism chances are lower. Reasoning being that rhythms are quite prominent in studying focus, while autism probably has a structural aspect.

But before you start attaching electrodes, do consider Ritalin. Among all psychiatric diseases, ADHD has pretty much the best claim to having seen meaningful therapeutic interventions.