Rosebud,
Just a quick reply and more later.
I am participating in a study that is correlating structural changes in the brains of PD patients with cognitive changes, sleep apnea and alterations in sleep patterns, memory. It looks like what happens, when and how much damage to substantia nigra is critical to the function of other parts of the brain and are reflected in the behavoir of PWP.
I will write more about this study later.
Girija