Hi everyone, good subject!
Annie., in regards to someone who cannot move, a paragraph in the link Diana provided says "One of these treatments is really intense physical therapy, but some people can't move at all. We found in our data that if they just think about moving, it keeps the neurons active right around the area that died in the brain. We used mental practice as a primer for physical training. As people improve and move along in their rehabilitation, they can progress from mental practice to physical practice and this can result in behavioral change, meaning they could move their arms better."
I lost use of my left side and whilst I was regaining use of my arm initially, nothing was happening, it seemed, with my leg. However I was so determined to recover that I used a fair bit of mental imagery and mental practise, I guess you could say. I thought - a lot - about moving, even imagining little creatures (Pacman & friends, actually!!) zooming through my veins and arteries, clearing them as they went, as in the early days, even though I'd had a haemorrhagic stroke and knew it wasn't a clot, tests for cholesterol, brain tumour etc, were still to come back. All my tests were eventually found to be in the normal-good range and no medical reason was found for the stroke however that didn't stop me visualising in this way with my little Pacmen!
In fact I would go so far as to say that a lot of my hospital time, when there weren't any visitors, medical staff calling by, tests, mealtimes, etc, I used this mental practise (and some meditation). I swung between sleeping at the drop of a hat or not sleeping, and often I would wake in the night so spent every chance I had really focussing on healing and regaining and attempting to do things that I knew my body actually could not do. I began this on Day 1, even whilst in the emergency department at hospital. :)
Some feeling returned to my leg, along with a sense that I could have a smidgeon of control over it and I could make it walk, albeit with walkers and a helper. Was it because of what I did or would it have been a natural progression over time, I'm not sure. But I couldn't lay there and do nothing and I sense/believe/know intuitively that it helped me a lot.