Psychopathic brains’ wiring leads to dangerous and violent actions

“It was a huge undertaking,” he said. “Most MRI scanners, they’re not going anywhere, but in this case, we’re driving this inside a prison and then in very quick succession we have to assess and scan the inmates.”

The team ultimately scanned the brains of 49 inmates over two hours as they took part in a type of delayed gratification test which asked them to choose between two options — receive a smaller amount of money immediately, or a larger amount at a later time. The results of those tests were then fit to a model that allowed researchers to create a measure of not only how impulsive each participant’s behavior was, but to identify brain regions that play a role in assessing the relative value of such choices.

What they found, Buckholtz said, was people who scored high for psychopathy showed greater activity in a region called the ventral striatum — known to be involved in evaluating the subjective reward — for the more immediate choice.

“So the more psychopathic a person is, the greater the magnitude of that striatal response,” Buckholtz said. “That suggests that the way they are calculating the value rewards is dysregulated — they may over-represent the value of immediate reward.”

When Buckholtz and colleagues began mapping which brain regions are connected to the ventral striatum, it became clear why.

“We mapped the connections between the ventral striatum and other regions known to be involved in decision-making, specifically regions of the prefrontal cortex known to regulate striatal response,” he said. “When we did that, we found that connections between the striatum and the ventral medial prefrontal cortex were much weaker in people with psychopathy.”

That lack of connection is important, Buckholtz said, because this portion of the prefrontal cortex role is thought to be important for ‘mental time-travel’ — envisioning the future consequences of actions. There is increasing evidence that prefrontal cortex uses the outcome of this process to change how strongly the striatum responds to rewards. With that prefrontal modulating influence weakened, the value of the more immediate choice may become dramatically over-represented.

“The striatum assigns values to different actions without much temporal context” he said. “We need the prefrontal cortex to make prospective judgements how an action will affect us in the future — if I do this, then this bad thing will happen. The way we think of it is if you break that connection in anyone, they’re going to start making bad choices because they won’t have the information that would otherwise guide their decision-making to more adaptive ends.”

The effect was so pronounced, Buckholtz said, that researchers were able to use the degree of connection between the striatum and the prefrontal cortex to accurately predict how many times inmates had been convicted of crimes.

Ultimately, Buckholtz said, his goal is to erase the popular image of psychopaths as incomprehensible, cold-blooded monsters and see them for what they are — everyday humans whose brains are simply wired differently.

“They’re not aliens, they’re people who make bad decisions,” he said. “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. 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.”

— Read more in Jay G. Hosking, “Disrupted Prefrontal Regulation of Striatal Subjective Value Signals in Psychopathy,” Neuron 95, no. 1 (5 July 2017): 221–31 (doi: org/10.1016/j.neuron.2017.06.030)