The brain's prefrontal cortex has been linked to the control of aggressive behaviors.
And, studies have suggested that damage to this part of the brain can cause people to become more violent and antisocial.
But it has remained unclear whether deficits in the prefrontal cortex drive violent behavior, or whether such problems — and the behavioral issues — are caused by a third and unknown factor.
So, researchers from the University of Pennsylvania in Philadelphia and the Nanyang Technological University in Singapore have wondered whether stimulating the prefrontal cortex with electric currents could help to curb violent impulses.
"If an offender's brain is scanned," states study author Olivia Choy, "we don't really know if it's the brain deficit that leads to the behavior or if it's the other way around."
"One of the main objectives of this study was to see whether there was a causal role of this brain region on antisocial behavior," she adds.
Their experiments, which were carried out on healthy adult volunteers, seem to suggest that this could actually be a viable, minimally invasive solution to an age-old problem.
Senior author Roy Hamilton notes, "The ability to manipulate such complex and fundamental aspects of cognition and behavior from outside the body has tremendous social, ethical, and possibly someday legal implications."
A paper detailing the team's methods and findings was published yesterday in the Journal of Neuroscience.
Brain stimulation curbs 'appetite' for violence
They conducted a double-blind randomized control trial, for which they recruited 81 healthy people, aged 18 or older. The volunteers were randomly assigned to either receive low-current stimulation for 30 seconds or more intense 20-minute stimulation to the prefrontal cortex.
Since 30-second, low-current stimulation would have no effect on brain activity, the group assigned to receive it was considered the "control" group. Neither the participants nor the people running the experiment knew who was assigned what.
After the brain stimulation, all the participants were asked to consider two imaginary scenarios: one involving physical assault, and the other involving sexual abuse.
They were asked to rate how likely they would be to picture themselves as the person perpetrating the violence in those scenarios, on a scale from 0 (completely unlikely) to 10 (extremely likely).
They were also asked to rate how morally reprehensible the acts depicted in those scenarios felt to them.
The participants who received 20-minute prefrontal cortex stimulation were less likely to consider both physical and sexual violence, compared with those in the control group.
These people had a 47 percent lower chance of considering physical assault, and a 70 percent lower likelihood of contemplating sexual abuse.
Commenting on the implications of these findings, psychologist and study co-author Adrian Raine says, "It's viewing violent crime from a public-health perspective."
"Historically we haven't taken this kind of approach to interventions around violence," he explains. "But this has promise. We only did one 20-minute session and we saw an effect. What if we had more sessions? What if we did it three times a week for a month?"
The 'opposite' of a lobotomy?
The researchers argue that the results of their study suggest that such an intervention — possibly in combination with other therapies, such as cognitive behavioral therapy — could be a minimally invasive way of curbing violent behavior.
"We're trying to find benign biological interventions that society will accept, and transcranial direct-current stimulation is minimal risk," says Raine.
"This isn't a frontal lobotomy. In fact, we're saying the opposite, that the front part of the brain needs to be better connected to the rest of the brain."
Still, the team acknowledges that, even with such promising findings, this is but the first step in a long process of figuring out what the best approach might be when it comes to using brain stimulation as therapy for individuals who are predisposed to violent behaviors.
The study should first of all be replicated, and the results consolidated, notes Choy.
"This is not the magic bullet that's going to wipe away aggression and crime," admits Raine. "But," he goes on to ask, "could transcranial direct-current stimulation be offered as an intervention technique for first-time offenders, to reduce their likelihood of recommitting a violent act?"