Much debate has raged over whether our minds and brains are two separate entities or one single entity: Is the mind independent of the brain, thus allowing for the concepts of spirit, soul, and even free will, or is the mind--our thinking--just an epiphenomenon of the electrochemical operations of the brain? Monism or dualism?
As a person with progressive Parkinson's disease, I can testify that my mind is independent of my brain. In fact, my mind (that's me) is very disturbed with my brain as the brain cells continue to die, making my brain increasingly resistant to my mental commands. For example, I want to turn over in bed the way I used to (easily), but even though my mind is giving my brain the same command it always has, my brain is not listening or communicating the message to the appropriate muscles.
A helpful analogy is to think of me, my thinking mind, as the driver of a car. The car is my brain. In the past, I would tell my brain where to go (which muscles to move) and it would comply. I was driving on new tires, and powered by a peppy new engine. Now, however, even though I (the driver) tell my brain (the car) where to turn, it does't do that very well. The car is running on one or two flat tires, and there seems to sand and water in the gas tank as well.
Another indication of the mind-brain dichotomy as evidenced in Parkinson's disease comes from word-finding difficulty. Some of the mind-brain unitizers (mind and brain are the same thing) have argued that words control our thoughts. We think of a word and then use it by pushing our thought into it. In other words, language precedes and therefore control thought, leaving us at the mercy of whatever words our brain produces after breakfast.
But as most people know, and Parkinson's patients in particular, we often know what we want to say, we are aware of the word that expresses the idea, but we just can't think of it, no matter how we obsess. So thinking precedes the verbalization of the thinking. Usually the clothing of words expresses the thought quickly, for the most part. But we all occasionally have trouble with matching the words to the thought.
So, I am in the unenviable position of watching my brain deteriorate and do less and less of what I tell it to. This should be good evidence that my mind and my brain are not the same thing. Consciousness and will and thought are who we are, drivers of a car made of meat (our brains), that are subject to change.