A person's level of political engagement can be informed by myriad factors, from education to environment. Now, a new study - published in the journal Brain and led by Northwestern University and Shirley Ryan AbilityLab - has for the first time identified which brain networks regulate political passion.
The study analyzed Vietnam War veterans with and without brain injuries. By comparing people who had very localized brain lesions with those who didn't, the study team was able to identify the brain structures that can modify the intensity of political feelings.
Damage to the prefrontal cortex, a region responsible for cognitive control and reasoning, led to an increase in the intensity of political feelings. Conversely, damage to the amygdala, a brain structure involved in emotional processing, decreased political intensity in participants. These findings held true even after accounting for factors like age, education, party affiliation, personality traits and other neuropsychiatric symptoms.
"While most people have not sustained brain injuries akin to those experienced by the veterans in the study, our findings tell us what neural circuits are at play for the population at large," said senior author Jordan Grafman, professor of physical medicine and rehabilitation at Northwestern University Feinberg School of Medicine and director of brain injury research at Shirley Ryan AbilityLab.
"We didn't find brain networks tied to liberal or conservative ideology, but we identified circuits that influence the intensity of political engagement across the political spectrum," Grafman added. "This suggests that factors like emotion shape how pre-existing political beliefs are expressed, rather than determining ideology itself."
Recognizing these brain mechanisms can help guide people in productive political engagement. For instance, one strategy would be to engage with others while reducing emotional attachment, or to take the position of an adversary in a discussion. Another approach would be to collaborate on a project both sides support.
The findings also have clinical implications. Currently, neuropsychiatric assessments rarely include questions about shifts in political behavior, but Grafman suggests they should. "Like other aspects of social behavior, assessments should consider asking whether a patient has experienced changes in their political attitudes since their brain injury," he said.
How the study was conducted
Grafman and his team studied Vietnam veterans with and without brain injuries as part of the Vietnam Head Injury Study, a long-term project on the neurobehavioral effects of combat-related brain injuries. Grafman has led this study since his time in the U.S. Air Force decades ago.
Between 2008 and 2012, neuroscientists conducted extensive behavioral questioning on these veterans, assessing various aspects of their political beliefs and intensity of feelings - roughly 40 to 45 years after their injuries. Participants reported both their current political behavior and their recollections of pre-injury political behavior.
The study included 124 male U.S. military veterans with penetrating head trauma and 35 combat-exposed control participants who had not sustained brain injuries.
Prior to the questioning, scientists had already mapped the veterans' brain lesions using lesion network mapping, a neuroimaging technique that identifies the broader brain circuitry connected to a given lesion. They then analyzed whether specific brain networks were linked to political beliefs based on the behavioral data.
Grafman, who has also studied links between the biological and cognitive underpinnings of religious fundamentalism, says understanding the brain's role in shaping beliefs "allows us to better assess meaningful aspects of life for patients and healthy individuals." Additionally, he says, "we expect this research will point to ways we can assist patients in recovering from brain injuries."
The other Northwestern University author is Shira Cohen-Zimerman. Additional authors are from Harvard University, Stanford University and the University of Modena in Italy.
The study was supported by the National Institute of Mental Health (Grant No. K23MH121657 and R01MH136248).
