A new study by a team of international researchers from the University of Pennsylvania and Nanyang Technological University suggests that electrically stimulating the prefrontal cortex can reduce the desire to carry out violent antisocial acts by over 50 percent. The research, while undeniably compelling, raises a whole host of confronting ethical questions, not just over the feasibility of actually bringing this technology into our legal system, but whether we should?
The intriguing experiment took 81 healthy adults and split them into two groups. One group received transcranial direct-current stimulation (tDCS) on the dorsolateral prefrontal cortex for 20 minutes, while the other placebo group received just 30 seconds of current and then nothing for the remaining 19 minutes.
Following the electrical stimulation all the participants were presented with two vignettes and asked to rate, from 0 to 10, how likely they would be to behave as the protagonist in the stories. One hypothetical scenario outlined a physical assault, while the other was about sexual assault. The results were fascinating, with participants receiving the tDCS reporting they would be between 47 and 70 percent less likely to carry out the violent acts compared to the blind placebo control.
"We chose our approach and behavioral tasks specifically based on our hypotheses about which brain areas might be relevant to generating aggressive intentions," says Roy Hamilton, senior author on the study. "We were pleased to see at least some of our major predictions borne out."
The electroshock stigma and its alternatives
It's not unreasonable for this research to conjure images of nightmarish forced electroshock therapy, nurtured by a steady stream of horror-infused pop culture painting a picture of a 1950s mental asylum and a crazed, evil psychiatrist forcing the violent treatment on anyone he can. The film One Flew Over the Cuckoo's Nest in 1975 further solidified a public sense that this is an inhumane and ineffective procedure, despite its decent success rates and continued use to this very day.
Transcranial direct-current stimulation is a little different to electroshock therapy or, more accurately, electroconvulsive therapy (ECT). Classical ECT involves significant electrical stimulation to the brain at thresholds intended to induce seizures. It is also not especially targeted, shooting electrical currents across the whole brain.
On the other hand, tDCS is much more subtle, delivering a continual low direct current to specific areas of the brain via electrodes on the head. The level of electrical current administered in tDCS sessions is often imperceptible to a subject and occasionally results in no more than a mild skin irritation.
Other forms of neuromodulation popular in experimental circles include deep brain stimulation (DBS) and transcranial magnetic stimulation (TMS). DBS is akin to a more invasive form of tDCS, with electrodes surgically implanted into a patient's brain so electrical currents can be precisely targeted at key regions.
DBS has been primarily explored as a symptomatic treatment for patients suffering from Parkinson's disease. For those that suffer from uncontrollable symptoms and haven't responded to conventional medications, this dramatic procedure can be somewhat effective in mitigating symptoms, but the invasive nature of the treatment makes it a last resort option.
TMS is probably one of the more widely researched neuromodulation techniques. It is entirely non-invasive, using a coil placed near the head to induce electrical activity in small, targeted areas of the brain. The technology is rapidly evolving with newer devices able to reach deeper and more precisely stimulate smaller regions of the brain with incredible specificity. TMS is currently being used for numerous applications, including depression and migraines.
Despite TMS being the more commonly used approach for neuromodulation in current clinical practice, perhaps tDCS is a more pragmatic and implementable form of the technology. Unlike TMS, tDCS is cheaper and easier to administer, it can often be simply engaged from home, and presents as a process that would be much more straightforward to integrate into widespread use.
Of course, the reality of what is being implied here is a lot more complicated than simply finding the most appropriate technology. Roy Hamilton quite rightly notes in relation to his new study that, "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."
Altering the brains of criminals…
A great deal of research has been done in the attempt to better understand what is going on within the brains of psychopaths. Several researchers have even dragged large MRI machines into prisons to try to study what is different about the brains of violent offenders. The results have been both compelling, and philosophically confronting, with studies finding that those criminals exhibiting continually bad decision-making abilities and high psychopathic tendencies do indeed have unconventional neural connections between different key brain areas.
Of course, while the burgeoning field of neurolaw is grappling with what this research means for legal ideas of individual responsibility, this new study raises a whole host of complicated ethical and social questions. If a short, and non-invasive, series of targeted tDCS sessions could reduce recidivism, then should we consider using it in prisons?
"Much of the focus in understanding causes of crime has been on social causation," says psychologist Adrian Raine, co-author on the new study. "That's important, but research from brain imaging and genetics has also shown that half of the variance in violence can be chalked up to biological factors. We're trying to find benign biological interventions that society will accept, and transcranial direct-current stimulation is minimal risk. 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."
Italian neurosurgeon Sergio Canavero penned a controversial essay in 2014 for the journal Frontiers in Human Neuroscience arguing that non-invasive neurostimulation should be experimentally applied to criminal psychopaths and repeat offenders despite any legal or ethical dilemmas. Canavero's argues, "it is imperative to "switch" [a criminal's] right/wrong circuitry to a socially non-disruptive mode."
The quite dramatic proposal is to "remodel" a criminal's "aberrant circuits" via either a series of intermittent brain stimulation treatments or, more startlingly, through some kind of implanted intercranial electrode system than can both, electrically modulate key areas of the brain, and remotely monitor behaviorally inappropriate neurological activity.
This isn't the first time Canavero has suggested extraordinary medical experiments. You might remember his name from his ongoing work to be the first surgeon to perform a human head transplant.
For the University of Pennsylvania and Nanyang Technological University team it is clear a great deal of research still needs to be done before these kinds of philosophical questions actively meet a real-life scenario. This particular study is admittedly very limited, with the researchers suggesting the results need to be replicated. The question of what impact repeated bouts of stimulation have over extended periods of time also needs to be answered.
"This is not the magic bullet that's going to wipe away aggression and crime," says Raine. "But could transcranial direct-current stimulation be offered as an intervention technique for first-time offenders to reduce their likelihood of recommitting a violent act?"
The key question of consent is one that many researchers aren't really grappling with. Of course, there's no chance convicted criminals would ever be forced to undergo this kind of procedure in a future where neuromodulation is integrated into our legal system. And behavioral alterations through electrical brain stimulation would never be forced upon people who don't comply to social norms – right?
This is the infinitely compelling brave new world of neuroscience.
The latest study was published in the Journal of Neuroscience.
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