Found: a brain circuit for spirituality

A new study led by investigators at Brigham and Women’s Hospital finds that spiritual acceptance can be localised to a specific brain circuit that is centred in the periaqueductal gray (PAG) — a brainstem region that has been implicated in functions including fear conditioning, pain modulation, altruistic behaviours and unconditional love. The team’s findings are published in the journal Biological Psychiatry.

“Our results suggest that spirituality and religiosity are rooted in fundamental, neurobiological dynamics and deeply woven into our neurofabric,” said corresponding author Dr Michael Ferguson, a principal investigator in the Brigham’s Center for Brain Circuit Therapeutics. “We were astonished to find that this brain circuit for spirituality is centred in one of the most evolutionarily preserved structures in the brain.”

To conduct their study, Dr Ferguson and colleagues used a technique called lesion network mapping that allows investigators to map complex human behaviours to specific brain circuits based on the locations of brain lesions in patients. The team leveraged a previously published dataset that included 88 neurosurgical patients who were undergoing surgery to remove a brain tumour. Patients completed a survey that included questions about spiritual acceptance before and after surgery. The team validated their results using a second dataset made up of more than 100 patients with lesions caused by penetrating head trauma from combat during the Vietnam War. These participants also completed questionnaires that included questions about religiosity.

Of the 88 neurosurgical patients, 30 showed a decrease in self-reported spiritual belief before and after neurosurgical brain tumour resection, 29 showed an increase and 29 showed no change. Using lesion network mapping, the team found that self-reported spirituality mapped to a specific brain circuit centred on the PAG. The circuit included positive nodes and negative nodes — lesions that disrupted these respective nodes either decreased or increased self-reported spiritual beliefs. Results on religiosity from the second dataset aligned with these findings. In addition, in a review of the literature, the researchers found several case reports of patients who became hyper-religious after experiencing brain lesions that affected the negative nodes of the circuit.

Lesion locations associated with other neurological and psychiatric symptoms also intersected with the spirituality circuit. Specifically, lesions causing Parkinsonism intersected positive areas of the circuit, as did lesions associated with decreased spirituality. Lesions causing delusions and alien limb syndrome intersected with negative regions, associated with increased spirituality and religiosity.

“These overlaps may be helpful for understanding shared features and associations, but these results should not be over-interpreted,” Dr Ferguson said. “For example, our results do not imply that religion is a delusion, that historical religious figures suffered from alien limb syndrome or that Parkinson’s disease arises due to a lack of religious faith. Instead, our results point to the deep roots of spiritual beliefs in a part of our brain that’s been implicated in many important functions.”

The authors noted that patients in both datasets were from predominantly Christian cultures; to understand the generalisability of their results, they would need to replicate their study across many backgrounds. The team is also interested in untangling religiosity and spirituality to understand brain circuits that may be driving differences. Additionally, Dr Ferguson would like to pursue clinical and translational applications for the findings, including understanding the role that spirituality and compassion may have in clinical treatment.

“I’m interested in the degree to which our understanding of brain circuits could help craft scientifically grounded, clinically translatable questions about how healing and spirituality can co-inform each other,” he said.

Image credit: Michael Ferguson

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