I think this applies to everybody. As for with "fixed" brain diseases, I know for JD he hasn't the capability to focus on true meditation, his individual condition symptoms prevents his mind from being able to. For JS silence is his enemy and causes his symptoms to surface. He may be able to meditate with background music if he tried.
I've been trying to meditate for years to combat anxiety/panick and insomnia,myself without a "fixed" brain disease with little sucess. My flashbacking is incessant and invades my thoughts in any meditation attempts. Quite like an acid trip.
I do find combining my attempts at meditation with video or audio stimulation is more effective for me personally. My mind needs the distraction to focus on while I use my relaxation and calming exercises.
The video is very good though I thoroughly enjoyed it.
Interesting article. The fact that meditation on the one hand seems to increase beta waves, associated with processing information, and on the other hand decreases the flow of information to various brain structures associated with readiness, consciousness and such is curious. It seems at first contradictory. But it's hard to know exactly without knowing more about the precise exercises they were doing. Focused concentration on a mental construct can become trance like.
Gajolene, have you ever tried binaural beats? They are a pretty useful halfway house to clearing the mind for meditatation, maybe they will be helpful. You can find a lot of them on YouTube as videos.