Blame the brain: Why psychopaths lack empathy

Psychopaths are usually described as lacking empathy, and a new study reveals the neurological basis for this dearth of feeling.

When people with psychopathy imagine others experiencing pain, brain regions associated with empathy and concern for others fail to activate or connect with brain areas involved in emotional processing and decision-making, researchers report.

In addition to a lack of remorse, psychopathy is characterized by shallow affect, glibness, manipulation and callousness. The rate of psychopathy is about 23 percent in prisons, compared with about 1 percent in the general population, research shows.

To investigate the neurological roots of the disorder, researchers studied 121 inmates at a medium-security prison in the United States. The inmates were divided into highly psychopathic, moderately psychopathic and weakly psychopathic groups on the basis of a widely used diagnostic tool called the Hare Psychopathy Checklist-Revised.

Researchers scanned the brains of the participants while showing them images depicting physical pain, such as a finger getting caught in a door or a toe caught under a heavy object. The participants were told to imagine the accident happening to themselves or to someone else. They were also shown images of neutral ojects, such as a hand on a doorknob.

When the highly psychopathic individuals imagined the accidents happening to themselves, their brains lit up in the anterior insula, the anterior midcingulate cortex, the somatosensory cortex and the right amygdala — all areas involved in empathy. The response was quite pronounced, suggesting psychopathic individuals were sensitive to thoughts of pain.

But when the highly psychopathic inmates imagined the accident happening to others, their brains failed to light up in the regions associated with empathy. In fact, an area involved in pleasure, the ventral striatum, lit up instead. Furthermore, these individuals showed abnormal connectivity between the insula and the ventromedial prefrontal cortex, an area important for empathetic decision-making.

By contrast, the less psychopathic individuals showed more normal brain activation and connectivity in these areas.

The strange patterns of brain activation and connectivity in highly psychopathic individuals suggest they did not experience empathy when imagining the pain of others, and possibly took pleasure in it.

The findings could help inform intervention programs for psychopathy, the researchers say. Having psychopathic people imagine themselves in pain first could be used in cognitive behavior therapies as a way of kick-starting empathy, they wrote in the study detailed today (Sept. 24) in the journal Frontiers in Human Neuroscience.

In fact, past research has shown psychopaths can feel empathy, when explicitly asked to, suggesting this ability to understand another person’s feelings may be repressed rather than missing entirely in psychopathic individuals.

Trauma in youth alters rat brain function, makes for aggressive adults

A team of behavioural geneticists has published a study revealing that in mice, psychological trauma in infancy leads to changes in brain function – an effect that makes them predisposed to aggression and violence in adulthood. Considering the impracticality of tracking a person’s brain function pre- and post-trauma, it is one of the best indicators yet that there is a link between psychological childhood traumas and brain function in humans, something that has been deduced but never proven.

“In humans, it is difficult to establish causality because there are many factors that interact, including cultural factors, social learning, etc,” Carmen Sandi, lead author on the paper and EPFL’s Brain Mind Institute director, told “Therefore, it is difficult to directly conclude that early life psychological trauma can on its own lead to physical or biological alterations and behavioural disturbances in later life. Although there is evidence in humans that those that have been submitted to early life trauma can have alterations in brain function, our study allows us to establish causality and the neurobiological level.”

In the study Sandi and her team subjected male rats to psychological stress before they reached puberty. Rats aged between 28 and 42 days old were exposed to one or two stressors for a continuous 30-minute period, across seven days in total. The stressors would occur without warning and included being left trapped on an elevated platform or exposed to the scent of fox urine (they fear the smell of one of its components). In total, 250 rats were involved in several rounds of experiments. When these same rats became adults, most began to express aggressive behaviours and Sandi and her team identified an increase in activity in their amygdala and little activity in the orbitofrontal cortex. The former is responsible for emotional impulses, while the latter (located in the prefrontal cortex) is related to decision-making, so quashes or regulates those impulses – it’s a kind of in-built social conscience that modifies our behaviour. The team also found that the levels of Monoamine oxidase A (MAOA) gene expression linked with aggression had increased above normal levels in the prefrontal cortex. Its delivery appeared to have been permanently altered by the early trauma.

“In a challenging social situation, the orbitofrontal cortex of a healthy individual is activated in order to inhibit aggressive impulses and to maintain normal interactions,” said Sandi. “But in the rats we studied, we noticed that there was very little activation of the orbitofrontal cortex. This reduces their ability to moderate negative impulses [instigated by an overactive amygdala].”

The two changes, in the amygdala and the orbitofrontal cortex respectively, have been recorded in violent humans – however this new study suggests a real link between psychological trauma and impulsive and aggressive behaviour later in life. Nevertheless, Sandi says she was shocked by the level of similarities between the rats in the experiments, and human neurological studies.

“We were incredibly surprised. For some of [the experiments], we first obtained our findings and only later on when reviewing the human literature (our study took over five years to be completed) discovered the large extent to which the effects are alike. We are very encouraged by these findings as they provide a very valid animal model to investigate mechanisms involved in the emergence of violent behaviours and an excellent opportunity to investigate potential treatments that, otherwise, would not be able for obvious ethical reasons to be explored in humans.”

Sandi’s study singled out several areas that need more detailed investigation and further interrogation. For instance, does the release of stress hormones during a trauma permanently alter gene expressions? And if so, how can those effects be reversed? The role of anti-depressants in controlling or even reversing the consequences of the brain trauma comes into play here, and will be a big area for Sandi going forward. In the experiments, she found that an MAOA gene inhibitor in the form of an anti-depressant dissipated the aggressive behaviour.

“We are currently investigating whether other pharmacological approaches based in our findings (for instance, targeting the epigenetic changes) could also have a beneficial effect. In any case, we believe that any pharmacological treatment given to humans would need to be combined with the appropriate behavioural or cognitive therapy. In our view, these drugs might be capable of opening opportunities for plasticity and learning in the brain, and thus to reprogramme those behaviours (and brain functions) that were maladaptively programmed by early exposure to trauma. We believe that the treatments on their own will not be sufficient, but that they should be coupled with the appropriate behavioural therapy and/or experiences.”

The study also revealed that different subjects reacted differently to traumas, as would be expected. It means that, although the average rat expressed more aggressive behaviour following childhood trauma, some will have a predisposition to it and some will express the opposite.

“When we looked at the individuals,” Sandi told, “we observed certain variability indicative of a differential vulnerability, with some animals developing a more aggressive phenotype while others behave as animals not exposed to early stress. This is extremely interesting as it reflects the human situation and will allow us in the future to investigate factors linked to the differential vulnerability to develop pathological aggression when exposed to early trauma.

Going forward, the team will investigate what makes some more susceptible to the effects of trauma than others, and look to identify the molecules "responsible for the long-term behavioural and brain programming when stress occurs”.

Interestingly, an earlier study also penned by Sandi, came up with similar results and thus supports her current work. In it, the team investigated links between childhood traumas and domestic abuse – again, using rats.

“Using an animal model devoid of human cultural factors, we showed that male rats became highly aggressive against their female partners as adults after exposure to non-social stressful experiences in their youth,” the study states. “Their offspring also showed increased aggression toward females in the absence of postnatal father-offspring interaction or any other exposure to violence.” Females exposed to this exhibited anxious and depressed behaviours, lost weight and expressed neurological symptoms related to being near unfamiliar males.

“With the caution required when translating animal work to humans, our findings extend current psychosocial explanations of the transgenerational transmission of intimate partner violence by strongly suggesting an important role for biological factors,” the study concluded.

Taking all this into account, Sandi says she is now investigating exactly how that offspring is affected. “We will soon know if they are also more aggressive against males or not – experiments are ongoing,” she said.

Image: Shutterstock

Source  aaronbflickr. Licensed under CC BY 2.0 via Wikimedia Commons

Split Brain

Meet the Corpus Callosum. This bundle of nerves is responsible for connecting the right and left sides of the brain. The destruction of the Corpus Callosum, especially that of one patient, “Joe,” has taught scientists a lot about the brain. Surgeons severed Joe’s corpus callosum because he had severe epilepsy, and by severing the corpus callosum, the excess electrical impulses causing the seizures travel wouldn’t throughout the brain. The surgery was a great success, and Joe’s seizures stopped, but scientists soon realized that something was different about Joe. He seemed to have a split brain.

One scientist in particular, Dr. Micheal Gazzaniga, has been studying Joe for over a decade. He has documented that whenever Joe looks at a word to the right of him, he can read it. But whenever Joe looks at a word to the left of him, which would normally be processed by the right hemisphere, he cannot read it. But what’s really fascinating is that when Joe closes his eyes and lets his hands do the work, he can unconsciously draw a pictorial representation of the word that he previously couldn’t see to his left. This work has lead to a theory that the two sides of our brains each receive and interpret their own input, but that it’s the corpus callosum that combines and integrates the information from the two sides of the brains so that we are doing conflicting things. Basically, our brain has two minds doing their own thing, and it’s up to the corpus callosum to integrate them together. Check out this article to learn more about split brains.

It makes the mind reel. How can a three-pound mass of jelly that you can hold in your palm imagine angels, contemplate the meaning of infinity and even question it’s own place in the cosmos? Especially awe inspiring is the fact that any single brain, including yours, is made up of atoms that were forged in the hearts of countless, far-flung stars billions of years ago.
—  V.S. Ramachandran from The Tell Tale Brain