One of the most striking aspects of Parkinson's disease is the capacity for cerebral compensation. By that I mean that alternative pathways and strategies are found to ensure that function is preserved.
We already know for instance that between 80 and 90% of all striatal dopamine must be lost before symptoms of Parkinson's even present in the clinic. It's not that we can do without 80% of our dopamine. It's more a case that the brain finds alternative, more energetically economical ways of achieving the same objective.The brain has a remarkable capacity for functional compensation.
Nowhere is this more obvious than in what we call kinesia paradoxica, that remarkable ability of even the most frozen Parkinson's patients to move rapidly in an emergency. Short lived and evanescent certainly, but striking nonetheless. Does it represent an entirely different motor pathway or is it merely the last dying embers of the dopamine system? The jury is out on this one. But the phenomenon is genuine and recognised by neurologists the world over. A simple motor behaviour accessed in an emergency context.
But imagine if more complex behaviours and motor programs could also be accessed when needed. I'm not talking about the brief few seconds of kinesia paradoxica but longer, more learnt and structured motor programs involving complex coordination of movement and balance.
Take a look at this video
of a man with severe freezing. Unable to initiate movement on its own, he is transformed when put on a bicycle. A complex motor behaviour, not a panic measure. This is not kinesia pradoxica but an entirely different motor program that is unaffected by his Parkinson's. An example of cerebral compensation and illustration of the fact that loss of motor function in Parkinson's is not even across the board. Some behaviour patterns are retained. Food for thought.