Origins of free will mapped in the human brain.
It is known that the current definition of free will is described as a combination of two cognitive processes, namely the desire to act, also know as volition, and a sense of responsibility for one’s own actions, also known as agency. Together, these neural-based processes create the process of free will, with damage to volition or agency sometimes leaving patients without the desire to move or speak or the sensation that their movements are not their own. Now, a study from researchers at BIDMC uses a novel brain lesion network mapping technique to map the neuroanatomy of perception of free will in the brain. The team state their results demonstrate that lesions in different locations causing disordered volition and agency localize to unique brain networks, lending insight into the neural pathways of free will. Their findings are published in the journal Proceedings of the National Academy of Sciences.
Previous studies show that in philosophy a person’s free will is described as a significant kind of control over one’s actions, in neuroscience it is defined as decision-making processes at work which may carry implications for a person’s sense of actions, moral responsibility, and the understanding of consciousness in general. However, the field of neurophilosophy remains highly controversial, with no consensus about the significance of findings, their meaning, or the conclusions drawn. The current study shows that brain lesions which disrupt volition occur in the anterior cingulate, and lesions that disrupt agency occur in the precuneus.
The current study identifies 28 cases in the medical literature where brain injury disrupted volition, leaving patients with akinetic mutism, a lack of motivation to move or speak. They also identify 50 cases in which brain injury disrupted agency and caused patients to feel their movements were not their own, a syndrome known as alien limb syndrome. Results show that while the brain injuries were quite diverse in their locations, the lesions fell within distinct brain networks.
Data findings show that all of the injuries disrupting volition were functionally connected to the anterior cingulate cortex, a region of the brain associated with motivation and planning, whilst 90% of lesions causing alien limb syndrome fell within a brain network functionally connected to the precuneus cortex, part of the brain associated with agency. Results show that brain stimulation to these same sites altered free will perception in healthy research participants, and neuroimaging of psychiatric patients with altered free will perception revealed abnormalities in the same brain networks.
The team surmise they have identified the regions in the brain responsible for free will. For the future, the researchers state that further studies are needed to discern whether the network of brain regions mapped in relation to free will for movements is the same as those used in moral decision-making, which in turn could be used in criminal situations.