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Brain imaging spots our abstract choices before we do
When it comes to making decisions, it seems that the conscious mind is the last to know.
We already had evidence that it is possible to detect brain activity associated with movement before someone is aware of making a decision to move. Work presented this week at the British Neuroscience Association (BNA) conference in London not only extends it to abstract decisions, but suggests that it might even be possible to pre-emptively reverse a decision before a person realises they’ve made it.
In 2011, Gabriel Kreiman of Harvard University measured the activity of individual neurons in 12 people with epilepsy, using electrodes already implanted into their brain to help identify the source of their seizures. The volunteers took part in the “Libet” experiment, in which they press a button whenever they like and remember the position of a second hand on a clock at the moment of decision.
Kreiman discovered that electrical activity in the supplementary motor area, involved in initiating movement, and in the anterior cingulate cortex, which controls attention and motivation, appeared up to 5 seconds before a volunteer was aware of deciding to press the button (Neuron, doi.org/btkcpz). This backed up earlier fMRI studies by John-Dylan Haynes of the Bernstein Center for Computational Neuroscience in Berlin, Germany, that had traced the origins of decisions to the prefrontal cortex a whopping 10 seconds before awareness (Nature Neuroscience, doi.org/cs3rzv).
“It’s always nice when two lines of research converge and to know that what we see with fMRI is actually there in the neurons,” says Haynes.
STOP sign for the brain
Kreiman told the BNA conference that he is now working on predicting decisions in real time, and to see if it is possible to reverse a decision before it hits consciousness – by flashing up the word “stop” on a screen as soon as telltale activity shows up in the brain.
There are no firm results yet, but Kreiman suspects there may be a measureable “point of no return” in the brain. “So far all we have is people saying, ‘that was weird, you read my mind’,” he says.
If this kind of “mind-reading” is possible, a new study by Haynes, published this week and also presented at the meeting, suggests that it may not be restricted to decisions about moving a finger. Using fMRI, Haynes has found that the very brain areas involved in deciding to move are also active several seconds before a more abstract decision, like whether to add or subtract a series of numbers.
He suggests that the prefrontal and parietal cortex may be general decision-making circuitry, passing activity on to different parts of the brain depending on the task at hand (PNAS, doi.org/k6b). “Perhaps decisions arise from a similar set of areas, then either flow into motor systems, for pressing buttons, or the parietal cortex for doing calculations,” he says.
Not hijacking the mind
Unless you happen to have electrodes inserted into your brain, there is no chance of decisions being hijacked by unscrupulous scientists, and Kreiman is keen to point out that he is not bent on world domination. “We’re not trying to do mind control; we are trying to find out the mechanisms of volition,” he says. “It might help people with Parkinson’s disease, where people lose voluntary movement.”
As for what it means for one of the longest-running debates in science – the question of whether we do or do not have free will – Haynes is pretty clear. “What we need now is 20 years of serious neuroscience, not more speculation about the handful of studies that have been done so far,” he says.
Kreiman agrees, but says that these early results at least bring the question of free will out of the realms of magic and mystery. “There is no magic. There are neurons, and there are ions that flow through membranes, and that it what is orchestrating our decisions,” he says. “We don’t need to invoke freedom.”
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