Image: Dr. Josh Buckholtz, PhD, and the Psychiatric Neuroimaging Division MRI scanner (Photo courtesy of MGH).
A new suggests that disrupted prefrontal regulation of the cortico-striatal circuit drives the dysfunctional decision-making common to psychopaths.
Researchers at Harvard University (Cambridge, MA, USA), Massachusetts General Hospital (MGH; Boston, USA), the University of Wisconsin (Madison, USA), and other institutions scanned the brains of 49 inmates in two medium-security prisons as they took part in a delayed gratification test, which asked them to choose between receiving a small amount of money immediately, or a larger amount at a later time. The results were then fit to a model that showed not only how impulsive each participant's behavior was, but also identified brain regions playing a role in assessing the relative value of each choice.
The results revealed that psychopathy was associated with stronger subjective value-related activity within the nucleus accumbens (NAcc) during inter-temporal choice, and with weaker intrinsic functional connectivity between NAcc and the ventromedial prefrontal cortex. The researchers suggest that this cortico-striatal circuit dysregulation drives erroneous decision-making in psychopathy (as indicated by more frequent criminal convictions), and could denote an important neurobiological risk factor. The study was published on July 5, 2017, in Neuron.
“We found that connections between the striatum and the ventral medial prefrontal cortex were much weaker in people with psychopathy,” said senior author associate professor Josh Buckholtz, PhD, of Harvard University and MGH. “The more psychopathic a person is, the greater the magnitude of that striatal response. That suggests that the way they are calculating the value rewards is dysregulated - they may over-represent the value of immediate reward.”
“They're not aliens, they're people who make bad decisions. The same kind of short-sighted, impulsive decision-making that we see in psychopathic individuals has also been noted in compulsive over-eaters and substance abusers,” concluded Dr. Buckholtz. “If we can put this back into the domain of rigorous scientific analysis, we can see psychopaths aren't inhuman, they're exactly what you would expect from humans who have this particular kind of brain wiring dysfunction.”
The striatum assigns values to different actions without much temporal context. It is the responsibility of the prefrontal cortex to make prospective judgments on how an action will affect the future. Increasing evidence suggests that the prefrontal cortex uses the outcome of this mental process to change how strongly the striatum responds to rewards. When this prefrontal modulating influence is weakened, the value of the more immediate choice may become dramatically over-represented.
Massachusetts General Hospital
University of Wisconsin