How ‘free will’ is implemented in the brain and is it possible to intervene in the process?

London, UK: Researchers have been able to identify the precise moment when a network of nerve cells (neurons) in the brain creates the signal to perform an action, before a person is even aware of deciding to take that action. Now they are building on this work to make initial attempts to interfere with consciously made decisions by decoding the pattern of brain activity in real time before an action is taken.

Professor Gabriel Kreiman told the British Neuroscience Association Festival of Neuroscience (BNA2013): “This could be useful to help elucidate the mechanistic basis by which neuronal circuits orchestrate ‘free’ will.”

Normally it is difficult to research the activity of neurons in the brain because it involves implanting electrodes – an invasive procedure that would not be ethical to do simply for scientific curiosity alone. However, Prof Kreiman, who is an associate professor at the Harvard Medical School, Boston, USA, together with neurosurgeon Itzhak Fried from University of California at Los Angeles (UCLA), had a rare opportunity to record the activity of over 1,000 neurons in two areas of the brain, the frontal and temporal lobes, when patients with epilepsy had had electrodes implanted to try to identify the source of their seizures.

“These patients have epilepsy that does not respond to drug treatment; Itzhak Fried implanted their brains with very thin electrodes (microwires) of about 40 micrometres in diameter in order to localise the focus of a seizure onset for a potential surgical procedure to alleviate the seizures. The microwires capture the extracellular electrical activity of neurons. Patients stay in the hospital for about a week. During this time, we have a unique opportunity to interrogate the activity of neurons and neural ensembles in the human brain at high spatial and temporal resolution,” explained Prof Kreiman. [1]

The researchers asked the patients to move their index finger to click a computer mouse and to report when they made that decision. “Based on the activity of small 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 said.

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,” said 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,” concluded Prof Kreiman.


[1] A micrometre is one millionth of a metre – approximately one hundred times smaller than the diameter of a human hair.

Abstract title: “Towards deciphering the neuronal circuits in human cortex underlying voluntary action”. Symposium: “Choosing and doing: the neuroscience of voluntary action” at 15.00 hrs BST, Tuesday 9 April, Cinema 1.