In this new paper by Dr. Fried and his colleagues, they have first repeated the experiment using recording from neurons in the brain rather than the EEG. Their finding about the timing of W was similar to all the other experiments. Since the EEG comes from neuronal activity, it should not be a great surprise that they were able to find neurons that changed their activity in the second or so prior to movement. They then took the data one step further. By analyzing a small number of the neurons, they could predict with a high degree of accuracy, prior to W, when a movement would occur. Hence, it appears that the neuronal activity prior to awareness of intention is marching toward the motor command. Recently, our group, led by Ou Bai, Ph.D., has done the same thing using EEG, although not with the same high degree of accuracy (Clin. Neurophysiol. 2011;122:364-72).
So what does this mean? If people have free will in making voluntary movements, doesn't the decision have to be made before the motor command? Here, it looks like the motor command is being made before the “decision.” The situation is actually easy to resolve, but it does involve some careful thinking. The first point to settle is that the mind is generated by the brain; it is not separate from the brain. Most people agree with that, even though it is easy to fall into dualistic thinking. We are our brains; what the brain is doing, we are doing. Hence, it appears that the decision to make a movement, in this circumstance, arises unconsciously. The decision becomes conscious, or at least we have the impression it becomes conscious, just slightly before the movement. The priority is important. That we have the perception of willing before the perception that the movement occurs allows us to draw the conclusion that we are causal in the production of the movement; that is, that we freely willed the movement.
Is this compatible with the idea that we actually have free will? It depends on what that means. If we are our brains, and our brain is choosing to do this without external coercion, then the movement is free. We become aware of this, in fact, only some of the time. Much of the time, we go about our business without worrying whether our movements are freely chosen or not. But, if we think about it, we can appreciate a sense of willing, or intention, that does occur prior to the movement. In fact, the timing of when we can appreciate the upcoming movement may depend on how we interrogate our brain. Dr. Masao Matsuhashi and I showed that if you probe a person, the knowledge that the movement is coming can be earlier than if you ask after the fact when the intention occurred (Eur. J. Neurosci. 2008;28:2344).
All of this has relevance for the clinical practice of neurology. My favorite example in this regard is trying to understand why patients with psychogenic movement disorders believe their movements to be involuntary when they look so voluntary.
MARK HALLETT, M.D., is chief of the Medical Neurology Branch and chief of the Human Motor Control Section of the National Institute for Neurological Disorders and Stroke. He has no relevant disclosures.
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