We may like to think of our sense of agency as something mystical, but new research reveals the brain circuits that underpin our free will.
Neuroscience can dive into deep, philosophical problems, only to emerge with palpable proof that even the most ethereal questions have a very concrete answer in the machinery of our brains.
Take religion, for example. Recently, Medical News Today have covered a range of studies showing that out-of-body experiences actually originate in the brain's superior parietal cortex networks, and that our perception of bodily boundaries changes with the size of our prefrontal cortex.
The "theory of mind" — or a person's ability to imagine what another person is thinking or feeling — has also preoccupied philosophers and psychologists for centuries.
Recent findings have not only shown which brain areas and circuits are involved in such a process, but they have also suggested that some of these brain regions may even predict a person's willingness to forgive others' mistakes.
Now, new research forays into the brain in search of answers to another age-old question: what is it that gives us the perception of free will?
Scientists who were led by Dr. Ryan Darby, an assistant professor of neurology from the Vanderbilt University Medical Center in Nashville, TN, set out to examine what occurs in the brain when people make the decision to move.
The senior study author is Dr. Michael D. Fox, the director of the Laboratory for Brain Network Imaging and Modulation at the Beth Israel Deaconess Medical Center in Boston, MA.
Free will down to interlaced brain networks
Dr. Darby and team used a cutting-edge neuroimaging technique called lesion network mapping to study the brains of people with two neurological conditions: akinetic mutism and alien limb syndrome.
People living with the former condition do not have the drive to move or speak, whereas in the latter syndrome, the person might think that someone else is moving their limbs for them.
Studying the brains of these people revealed that injuries that end up affecting a person's volition, or their drive to act, spread throughout a clearly identifiable brain network.
On the other hand, injuries that affect an individual's agency — that is, the perception that we are responsible for those acts — occur within a different brain network.
"Our approach," says Dr. Darby, "challenges the assumption that neuropsychiatric symptoms should localize to one brain region, and instead shows that these symptoms localized to interconnected brain networks."
"Once we understand that agency and volition localize to brain networks," he goes on to ask, "can we then take that knowledge and develop a new approach to treating a symptom?"
The scientists stimulated different areas of these previously identified brain networks and revealed that such stimulation could indeed alter a person's perception of agency, or free will.
They also studied the brains of people with psychiatric conditions that also involved impairment in their free will, such as motor conversion disorder or catatonia.
The results revealed abnormalities in the same brain networks that had previously correlated with volition and agency.
"There are very few approaches," explains Dr. Darby, "where you can compare a similar type of symptom in a neurological patient and a psychiatric patient." His previous research used lesion network mapping to study criminal behavior.
"Our study shows the promise of using our network localization method in neurological patients to better understand symptoms in psychiatric patients."
Dr. Ryan Darby
"That being said, it's the first time we have used our technique with neuroimaging abnormalities in psychiatric patients. It would require further study and validation, but I think the promise is there," he adds.