In rare cases, brain lesions can lead previously law-abiding individuals to criminal behavior. Researchers, led by Ryan Darby, MD, an assistant professor of neurology at Vanderbilt University Medical Center, examined MRI and CT scans to see if such injuries can lead to deteriorated decision-making and a disregard for morality.
Published in the December issue of Proceedings of the National Academy of Sciences, the study two groups of participants. The first included 17 individuals with a definitive correlation between criminality and a brain lesion. The second, with 23 participants, had an implied correlation, with researchers unsure if the lesion occurred before or after criminal behavior. The injuries were in different areas of the brain, but connected to the same neural network.
“These results link lesions resulting in criminal behavior to regions whose activity is correlated with moral decision making, value-based decision making, and theory of mind in normal subjects,” Darby et al. wrote. “Exactly which psychological processes are abnormal or disrupted in criminals remains a matter of ongoing research and debate.”
The researchers, however, cautioned against overinterpretation of the results, leading to predict criminal behavior without including genetic factors, social support, lesion etiology and other factors.
"We looked at networks involved in morality as well as different psychological processes that researchers have thought might be involved—empathy, cognitive control and other processes that are important for decision making," Darby et al. wrote. "We saw that it was really morality and value-based decision making—reward and punishment decision-making—that the lesions were strongly connected to."
The full study is available for free at PNAS.