Researchers at Cognitive Neuroscience Centre in France have carried out the study and found that free will resides in the parietal cortex of the human brain, according to a report in New Scientist.
Their findings are based on an analysis of an experiment on seven patients undergoing brain surgery to remove tumours. The scientists found that when they electrically jolted the parietal cortex in the patients undergoing surgery, the patients felt a desire to wiggle their finger, for instance; roll their tongue or move a limb.
Stronger electrical pulses convinced patients that they had actually performed these movements, although their bodies did not move. "What it tells us is there are specific brain regions that are involved in the consciousness of your movement," said Angela Sirigu, who led the study.
In all but one case, the cancers were located far from the parietal cortex and other areas. One patient's tumour was located near the parietal cortex, but it did not interfere with the experiments.
Because the patients were awake during the surgery, they were able to answer questions. "Did you move?" the researchers asked a 76-year-old man after lightly zapping a point on his parietal cortex. "No," he responded. "I had a desire to roll my tongue in my mouth."
After a stronger pulse to the parietal cortex, a 42-year-old man exclaimed: "My hand moved," yet Sirigu's team saw no signs of movement. The scientists also discovered stimulating another brain area -- the premotor cortex -- provoked involuntary, unconscious movements in the same patients.
The study points to two brain areas involved in the decision to move a limb and then execute the action. Sirigu speculates that the parietal cortex makes predictions about future movements and sends instructions to the premotor cortex, which returns the outcome of the movement to the parietal cortex.
"In day-to-day life, we rely on both brain regions to move about. You need both systems, the parietal and premotor cortex to generate intention and check whether this is followed through," Sirigu said.
The findings are published in the journal Science.
"No"
This is interesting but I fail to see what it has to do with free will. It says there is a part of the brain that codes for intentions or desires. Well of course there is. Otherwise we wouldn't HAVE intentions or desires. But the presence of an intention is not evidence for a "free choice".
If anything the experiments show the opposite: that our belief that we make free choices is suspect, because you can MAKE people believe they intended to do something by sticking a few millivolts into their brains.
What the research actually shows is that (certain aspects of) volition - i.e. the intention to act, as opposed to the carrying out of the action - can be localised to the parietal cortex. But if you break it down, carrying out an action is also an intention. For instance I "choose" to go to the kitchen. To do this I must make a plan, consisting of many movements. Each step in that plan is an intention (e.g. to walk), made from other plans/sequences, each step in which is also an intention (e.g. to raise the left leg). As the plan is being executed, many of these intentions become acted out, and when each action is complete, this information needs to be fed back to the higher level to tell it it's time to start the next step. Eventually the overall intention to go to the kitchen becomes satisfied, so the feedback returns to the point of origin.
Mildly stimulating some parietal neurons clearly triggers the generation of a small plan (to roll one's tongue, say). Overstimulation presumably also triggers the feedback neurons that tell us the plan has been completed, so we believe we DID roll our tongue.
All of this is exactly what one would expect in any system capable of generating and executing hierarchical plans. The fact that it can be localised to part of the parietal cortex probably just suggests they've found a level inside that hierarchy where they were able to discern the effect (because of the nature of the experiment). Other cortical regions would probably stimulate larger or smaller kinds of desire (the desire to be happy, the desire to move a specific muscle) or even perceptions (the belief that one is moving, or that one is going to be hit), because perception and action are both very similar cybernetic systems - each involves a belief or an intention (an intention is a belief about what you are about to do), and each involves feedback about completion (a fusing of top-down with bottom-up signals).
I believe I wrote a book about this once. Or at least I intended to...
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