A team of scientists recently packed a mobile MRI scanner on the back of a tractor trailer and hauled it into a medium security prison with the goal of scanning a high volume of criminals that have been classified as psychopaths. It's estimated that while psychopaths only make up one percent of the general population, their prevalence in committing crimes mean they make up between 15 and 25 percent of the male North American prison population. So what is going on inside the brains of psychopaths?

This wasn't the first time researchers have trucked MRIs into prison to study the brains of psychopaths. We seem to be endlessly fascinated with understanding how psychopaths think and our growing insight into the neuroscience behind psychopathy is fundamentally altering ideas of personal responsibility and metal illness.

The psychopath who studies psychopaths

An infamous moment in the history of psychopath neuroscience came in 2006, when scientist James Fallon was poring through a pile of PET scans. Fallon had been studying the neuroanatomical basis of psychopathy for some time and he was starting to get a good handle on what kind of brain activity would signal those tendencies. On his desk, among the brain scans of murderers, depressives and schizophrenics, were scans of him and his family, part of a separate study being done on Alzheimer's disease.

"I got to the bottom of the stack, and saw this scan that was obviously pathological," Fallon said in an interview with Smithsonian.

Looking up the code behind the scan he discovered that he was in fact viewing his own brain. Fallon's research then turned on himself and he went on to investigate several neurological and genetic markers that correlated with psychopathic tendencies. Fallon's personal relationship with psychopathy also led him to investigate the strange combination of nature and nurture that ultimately leads a psychopathic person to express themselves through violent antisocial behavior.

After all, if his brain looked like that of a psychopath, then what separated him from a violent psychopathic criminal?

A psychopath is classically defined as a person with an extreme inability to empathize with other human beings. They also lack remorse for their actions, will comfortably exploit others for their own personal gain, and have a high level of self-confidence. Sound like anyone you know?

It's not unexpected that psychopaths have become objects of fascination for many of us. Depictions of these characters fill our television and film screens from Gordon Gekko and Patrick Bateman to Breaking Bad, House of Cards or Dexter. The public is a little obsessed with psychopathy.

With our society seemingly structured to reward the type of cut-throat behavior perfectly exemplified by psychopathy, it is no surprise that some studies have found that up to one in five corporate professionals display "clinically significant psychopathic traits".

When writer Jon Ronson investigated the topic he discovered that psychopaths comprise around 4 percent of corporate CEOs. That may sound low, but when its estimated that only about 1 percent of the overall population can be considered psychopathic, that's still a significantly higher number rising through the corporate ranks. Ronson even goes so far as to claim our system actively rewards psychopathic behavior.

"The way that capitalism is structured really is a physical manifestation of the brain anomaly known as psychopathy," Ronson said in an interview back in 2011 while promoting his exceptional book The Psychopath Test.

One of the primary psychopathic characteristics that many scientists tend to focus on is the notable lack of empathy, with those affected seeming to display a significant inability to connect emotionally with other human beings. But is there anything structurally different in their brains to cause this lack of empathy?

The prison scans

A study from King's College in 2012 found that violent male offenders who met the diagnosis for psychopathy displayed significantly reduced gray matter volumes in the anterior rostral prefrontal cortex and temporal poles. This striking, and specific, structural abnormality in the part of the brain associated with empathy and feelings of guilt, points to a clear neurological difference between regular violent offenders and genuine psychopaths.

A straightforward lack of empathy isn't enough to make someone a full-blown psychopath though. Several MRI studies have shown a more complex combination of neurological activities is occurring inside the brain of a psychopath.

A 2013 study took MRI scans of 121 prison inmates split into three groups: rated as highly, moderately or weakly psychopathic. The inmates were shown images displaying physical pain and then asked to imagine that accident happening to themselves or others. The highly psychopathic subjects displayed a pronounced empathic response to the thought of pain when imagined to themselves. Brain activity across several regions involved in pain empathy was identified as heightened, including the anterior insula, the anterior midcingulate cortex, somatosensory cortex, and the right amygdala.

It was clear psychopaths understood and empathized with the concept of pain when inflicted upon themselves. When asked to imagine that same pain inflicted upon others those psychopathic subjects displayed a very different response. Not only did those empathic areas of the brain fail to activate, but increased activity was seen in another area of the brain, the ventral striatum.

The ventral striatum is a fascinating part of the brain, known to manage reward processing, motivation and decision-making. This particular study suggested that psychopaths could actually enjoy imagining pain being inflicted upon others.

But how this actually motivates a violent or antisocial action turns out to be a little more complex than simply deriving pleasure from other people being hurt.

After all, not all those that display psychopathic characteristics turn out to be violent criminals. Dr James Fallon can attest to that. So what else is going on inside the brain to cause a psychopath to make an antisocial decision?

One study from 2016 discovered no difference in excitability of the ventral striatum between criminal and non-criminal psychopaths when undertaking a reward game. However, a significant difference between the two groups was identified in the connectivity from the ventral striatum and another brain region called the dorsomedial prefrontal cortex.

This area of the brain is known to manage cognitive control of behavior, performance adjustment, impulse control and general self-inhibition. In highly psychopathic criminals an abnormally high connectivity was identified between the reward-signaling ventral striatum and the behavior-controlling dorsomedial prefrontal cortex.

"These observations raise the hypothesis that psychopathic criminals might exhibit a failure to adjust performance due to aberrant impact of reward expectation," write the scientists behind this 2016 study.

As well as over-valuing the reward signals from the ventral striatum, a recent Harvard study found that people with psychopathy are unable to accurately evaluate the future consequences of their actions.

This MRI study examined 49 prison inmates and discovered a weak connection between the ventral striatum and the ventral medial prefrontal cortex in those inmates with high psychopathic tendencies. Senior author of the Harvard study, Josh Buckholtz describes this part of the prefrontal cortex as vital for "mental time-travel" – that ability to evaluate the future outcomes of an action relative to the more immediate rewards.

The effect identified in the study was so pronounced that the researchers could accurately predict how often an individual inmate had been convicted of crimes relative to the strength of the connection between the striatum and prefrontal cortex. So the stronger the connection, the more the reward signals were dominating all aspects of a decision.

Buckholtz sees this as a "particular kind of brain wiring dysfunction" that results in bad decision making, regardless of psychopathy.

My brain made me do it

These scientific conclusions leave us in a strange and conflicted position. Psychopathic tendencies clearly don't necessarily lead to criminal or anti-social behavior, rather it seems that a more complicated set of neurological conditions lead to the actual expression of psychopathy in negative, antisocial or criminal action. A lack of empathy, over-acting reward centers, and an inability to evaluate future consequences all line up and lead one to make a decision that normal people would classify as psychopathic.

The legal and social implications of this research are unsettling for many. If we can classify criminal or abhorrent behavior as mere neurological dysfunction, then our entire basis for asserting legal responsibility falls apart. Intent is currently a vital aspect in asserting judgement across our legal system. If someone can defer a degree of conscious responsibility regarding their actions to simply the way their brain is wired, then where does that leave us?

The emerging field of neurolaw is grappling with that very question as neuroscientific defenses are becoming increasingly prominent in courtrooms. One fascinating study from 2012 found that judges tended to deliver more lenient sentences when a biomechanical cause of psychopathy is presented. The implication is that an individual is somewhat less personally culpable in these instances. We could call it the "My brain made me do it" defense.

We may have conscious control over our choices, but it is becoming increasingly clear that there is a variety of neurological mechanisms that influence how we evaluate the information that guides our decisions. Psychopathy is currently not officially classified as a mental illness, but some scientists are arguing that is should be, as a neural dysfunction behind the disorder has clearly been identified. But at what point are we simply regulating ways of thinking?

This increasing research into the neurology of psychopathy is not only helping us understand why some people do terrible things, but shedding light on why we all do what we do. The most confronting idea raised is that if we can identify how certain brain wiring can result in a person undertaking criminal or antisocial behavior, then the flip side is we must also associate altruistic or selfless actions to similar neurological functions.

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