groups of neurons, we could predict this decision several hundreds of milliseconds and, in some cases, seconds before the action. In a variant of the main experiment, the patients were allowed to choose whether to use their left hand or right hand and we showed that we could also predict this decision."
The researchers found that an increasing number of neurons in two specific brain regions started to become active before the person was aware of their decision to move their finger. The two regions were the supplementary motor area, which is thought to be the area for preparing to perform motor actions, and the anterior cingulate cortex, which has a number of roles including the signalling processes associated with reward.
Prof Kreiman believes that these results provide initial steps to elucidate the mechanism for the emergence of conscious will in humans. "The activity of multiple neurons in extremely simple neural circuits precedes volition -- in this case the decision to make a simple movement -- until a threshold is crossed and the action is taken," he will say.
Knowing when this threshold will be reached could enable researchers to see whether it is possible to interfere and maybe change the decision before any action is taken. "We are now making initial attempts to interfere with volition by decoding the neural responses in real time and asking whether there is a 'point of no return' in the hierarchical chain of command from unconscious decisions to volition to action," says Prof Kreiman.
How these findings fit into the concept of "free will" is more complicated. "The concept of free will has been debated for millennia. Ultimately, current scientific understanding strongly suggests that 'will' has to be orchestrated by neurons in our brains (as opposed to magic or religious beliefs or other notions). We have provided initial steps to try to disentangle which neurons are involved, to show where and how 'will' or 'volition' could be implemented in the brain.
"Our work does not say that life is predetermined, that we can predict the future and that we can, for instance, determine what you are going to eat for lunch two weeks from now, or who you are going to marry.
"We are saying that volition (like other aspects of consciousness) is a brain phenomenon that is instantiated by physical hardware, i.e. neurons. We are making claims about volition for very simple tasks, such as moving an index finger or choosing which hand to use, over scales of hundreds of milliseconds to seconds. Nothing more. Nothing less.
"Ultimately, our actions depend on multiple variables, several of which are external (for instance, it rains, hence, I will take my umbrella) and cannot be decoded or predicted from neurons. However, our volitional decision of whether to take the red umbrella or the blue one today -- ultimately perhaps the real core of free will -- is dictated by neurons," Prof Kreiman will conclude.
 A micrometre is one millionth of a metre -- approximately one hundred times smaller than the diameter of a human hair.
 The research was funded by the US National Institutes of Health and the US National Science Foundation.
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