Sorry for long post
It's a shame PUK is taking down that information sheet. It's so interesting and positive, even if you feel it's out of date. Some websites keep an archive section for material like that.
I don't want to speak for Sea angler, but when I'm talking about asymmetry, I'm meaning that in parkinsons (and lots of parkinsonisms), it's often one side of the body has symptoms first and worst, and this is related to changes on the opposite side of the brain.
As well as the asymmetric physical changes, I'm interested in the changes to thoughts and feelings this causes. Our left and right brain do different things in terms of feeling and thought, and from (dodgy) memory, there's writers and researchers, (Damasio? Le Doux?) saying that a lot of our feeling and thoughts are in our bodies as well our brains, and that it is a two way thing, not a top down system with the brain totally in charge.
The more recent work on empathy and mirroring is saying that we experience empathy in our bodies too. When we see someone injured in the arm, there's a change in the part of our brain that would be affected if it was our arm that was hurting and there are physiological changes in our arm too.
Some people with parkinsons talk about feeling a flatness or clumsiness in our emotions, and changes to our sense of connection to others - a struggle to understand others' feelings and thoughts from tone of voice, facial expressions and other movements. Some researchers are saying this may come partly from this mirroring process not working so well. If you have facial masking, or you don't make the hand gestures you used to, the muscles of your face and arms won't physically respond in the same way to others expressions and this continual feedback loop between your muscles and your brain telling you what's going on for them, doesn't work so well.
With the left and right brain doing different cognitive and emotional jobs in everyone, it makes sense to me that which side is most involved in your parkinsons might affect your sense of self and how you relate to others.
Given what's been found out about the way the body is involved in creating our feelings and thoughts, this experience of feeling more like how I used to be before parkinsonism, when I focus in on the less affected side of my body doesn't sound so daft. I don't need medical research to start to trust what I experience, and use what works for me, but it's interesting to come across links between the two.
I had a quick look on google scholar. There's lots of research on assymmetry in parkinson's and parkinsonism and how this affects which physical and cognitive problems we're most likely to get, and the speed of the changes. But I haven't yet found the articles that talk about what I'm wondering about. I'll have another look when my brain is in gear. I'm struggling too with finding the words for thoughts.
It would be so good if there was more qualitative research on parkinsons - where it's focused on what we experience and think, not just on what can be measured.
all best, rhubarb