Thoughts are objects in the world but they have a special status: they can signify experiences of objects in the world (e.g. the thought, “the sun is yellow” signifies an experience of the sun and not the object itself). Non-thought objects cannot signify experiences but they can be the subject of experiences. In other words, the transition from objects in themselves to an “object” in thought requires a thinker to experience and signify the object.
There is another type of signification of thought: when I think, “type this word” it signifies a complex set of muscle movements which direct my fingers to tap the keyboard; the thought “type this word” is a thought signified by consciousness as my thought and is also a signifier of bodily movement. The resulting movement is limited by the effectiveness of the thought and also the specific arrangement of bones, muscles and tendons etc in my body, whose arrangement was determined before I was born.
Therefore, thoughts can signify experiences and bodily movement; as such thoughts are free and also restricted; free to be whatever is possible as experience (within the limits of language and understanding) and restricted by the specific state of the body the thought finds itself in. My body limits the signification of thought as bodily movement but leaves intact thought as experience; this happens in both non-sufferers and sufferers of Parkinson’s, the limit is just deeper because of Parkinson’s.
Therefore, as I gradually lose control of my body I lose my identity as signifier of bodily movement but retain myself as a being who experiences the world.