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Do Psychopaths Have Abnormal Brains?


According to biology assignment help specialists, personality disorder subcategory is psychopathy. Psychopaths make up around 1% of the population. Philippe Pine, one of the pioneers of modern psychiatry, introduced the idea of psychopathy in the 19th century. He spoke about a group of patients who had mania sans délire (insanity without delirium). They were not intellectually challenged, but their lack of moral and behavioural restraint stemmed from brutality, antisocial behaviour, and alcohol and drug misuse (Kiehl and Lushing, 2014). In 1976, Hervey Cleckley published The Mask of Sanity, a book that had a significant impact. He defined psychopathy as a combination of interpersonal, emotional, and behavioural traits and said that psychopaths typically do not exhibit the symptoms or indicators that most people identify with psychopathy. For instance, not all of them have illusions or hear voices. According to Cleckley, psychopaths may pass as normal while yet concealing a mental disease behind a "mask." He notices that psychopaths seem approachable and simple to converse to. In addition, he says that psychopaths often possess great intelligence and the ability to effortlessly deceive people by their manner of speaking rather than actual words. They are more hazardous than those who have been diagnosed with serious mental diseases since their personality issue is concealed and they might look normal (Moscovici, 2011).

A psychopathy test was created in 1980 by Dr. Robert Hare and made available to the public in 1991. This became the "gold standard" for forensic psychiatrists, researchers, and the legal system in identifying the characteristics and behaviours of psychopaths. This was known as the PCL-R (psychopathy check list- revised), also known as The Hare (Egan, 2016). For the exam, Hare prepared a 20-item checklist. For each item, a score is assigned: 0 for not applying to the individual, 1 for somewhat applying, and 2 for completely applying. Inability to accept responsibility for actions, emotional shallowness, callousness and lack of empathy, a tendency toward boredom, a parasitic lifestyle, impulsivity, irresponsibility, lack of behavioural control, behavioural issues in early life, juvenile delinquency, criminal versatility, and a history of crime are among the traits on the list. A psychopath diagnosis would be possible with a score of 30 or above. The standard score for a "regular" individual is often less than 5, whereas the mean score for inmates is 23. (Egan, 2016)

Psychopathy is seen by many scientists and psychologists as a neurodevelopmental condition. One of them is Kent Kiehl, who finished both his doctoral and master's degrees at Hares' lab. By visiting nearby jails with an fMRI (functional magnetic resonance imaging) equipment and exposing the convicts to both violent and neutral words and pictures, he has examined the brains of over 5000 inmates. According to Kiehl, anatomical and functional anomalies in the brain of psychopaths have an impact on their emotions, impulse control, and cognition. Any anomalies in the amygdala, which is involved in the emotional processes, might be linked to psychopathy. Two investigations using neuroimaging provided proof of this (Blair, 2003). In the first research, conducted in 2000, Tiihonen and coworkers compared the association between psychopathy and amygdala volume in violent offenders. They came to the conclusion that high degrees of psychopathy were correlated with amygdala volume reduction. The same result was reached in the second investigation, which was conducted by Kiehl (2001). Additionally connected to alterations in behaviour and psychopathy is the frontal lobe. Phineas Gage, who had frontal lobe injury after an accident, is an example of a person who changed their behaviour. Even if other aspects of her personality stayed the same, this led to a personality change (speech, movement, intelligence etc). Only after his passing was this reason put forward (Damasio et al., 1994).

Another hypothesis is that a person's early years are the root of their psychopathy. Around the age of four, a person begins to acquire the capacity for both deception and empathy. People with personality disorders, however, do not naturally exhibit this, and it is believed that this results from traumatic events or from how adults treat them, for as via abuse or neglect. In 2013, Craparo, Schimmenti, and Caretti conducted research on the early lives of criminal offenders in Italy. The findings indicated that offenders with high PCL-R checklist scores were more likely to have experienced neglect or abuse as a kid. They came to the conclusion that traumatic experiences in childhood may result in the development of psychopathic tendencies. This was in line with a prior research from 1996 that examined psychopathy and aggression among abused and neglected young people. A matched control group of 489 people and an experimental group of 652 people were compared. PCL-R scores were higher in the experimental group than in the control group. These findings indicated a link between childhood maltreatment and neglect and psychopathy (Weiler and Widom, 1996).

According to Chivers (2014), not all psychopaths will go on to conduct crimes, despite the fact that it is estimated that they make up 1% of the population. Due to their charisma and glibness, some go on to have very successful lives as CEOs and professional sports. Therefore, because it is difficult to foretell whether someone will commit a crime, the justice system cannot penalise someone in advance just because they exhibit psychopathy characteristics and behaviours. It is simpler to estimate a person's chance of reoffending after they have crossed that line and committed a crime.

Theories of Psychopathy

There are two basic ideas that explain psychopathy, according to academics. The first theory is Antonio Damasio's somatic marker hypothesis (1994). He proposed that emotional factors influence how decisions are made. Phineas Gage's accident was the first to show that the frontal lobe is connected to decision-making. Damage to this region, particularly to the prefrontal cortex, therefore decreases one's capacity to accomplish that. It was discovered that those who have prefrontal impairment are unable to convey the right emotions. These psychopathological characteristics gave rise to Damasio's idea. He described emotions as a range of physical changes brought on by the brain's reaction to a stimuli. Eventually, the consequences from a prior scenario are linked to emotions and the matching alteration in the body (somatic marker). Therefore, the body impacts decision-making in favour of a specific behaviour if that circumstance were to recur in the future. For instance, the brain is more likely to repeat a behaviour if it previously produced a good mood or physical signal that left the person feeling joyful. It could also have the reverse effect. For instance, the brain is more likely to oppose a person's behaviour in a circumstance that is similar in the future if a previous experience left them feeling dissatisfied or depressed. (2005) Bechara and Damasio The Iowa gambling task research, which looked at the somatic markers in people with various levels of psychopathy, made a suggestion on the connection between the somatic marker hypothesis and psychopathy. It was shown that psychopaths with high PCL-R scores had the same gambling tendencies as those with frontal brain lesions (van Honk et al., 2002).

The violence inhibition mechanism postulated by Blair is the second hypothesis for the origin of psychopathy. Eibl-Eibesfeldt and Lorenz's study served as the foundation for it. According to their hypothesis, animals have evolved systems that allow them to manage aggression (Weber et al., 2008). An illustration of this is when a combative dog backs off after its adversary bares its throat. The system that prevents violence is assumed to be comparable in humans and is thought to be triggered by distress signals. The amygdala is the key neurological region for this notion (Blair, 2001). Consequently, any irregularities may cause a decrease in the capacity for empathy (Weber et al., 2008). Numerous research support the mechanism that prevents violence. One research examined whether young toddlers with psychopathic traits could recognise emotion in facial expressions. There were 37 kids in the research, aged 9 to 15, who attended a school for kids with behavioural issues. The findings indicated that children with psychopathic tendencies have trouble identifying both depressive and terrified facial expressions (Stevens, Charman and Blair, 2001).

The History of Neuroimaging and Brain Mapping

Lesions in persons from trauma or illnesses have produced the earliest data on brain mapping that is now available. There are three well-known cases: Tan, H.M., and Phineas Gage. Tan, whose loss of language was caused by injury to the left frontal brain, pioneered the knowledge of the localization of language abilities. The most well-known example, however, was H.M., whose bilateral medial temporal lobectomy resulted in a lifelong loss of memory for new knowledge. As Savoy continues, MRI (Magnetic Resonance Imaging) provides improved information on the extent of disorders and injuries, despite patient evidence for brain mapping continuing to be a source of significant information (Savoy 2001).

In order to track and record changes in the brain's blood oxygenation, functional MRI (fMRI) was created in 1990. Patients are exposed to stimuli (words, images, movies, etc.), and any activated brain areas are mapped and compared with brains that are at rest. It has shown to be effective, particularly in psychopathy. In criminal psychopaths, the first fMRI research was released in 2001. (Kiehl and Kofman 2011). This research, conducted in 2001 by Kiehl and colleagues, looked at how criminal psychopaths processed their emotions while doing memory tests. Eight psychopaths, eight non-psychopaths, and eight healthy control volunteers were recruited from a maximum-security jail. The convicts were divided into psychopaths and non-psychopaths using the PCL-R from Hare. The findings indicate that anomalies in the limbic system and parts of the frontal cortex are primarily responsible for criminal psychopathy.

Electroencephalography (EEG), which is non-invasive and widely used in neurological illnesses, is another method of mapping the brain. It may either be used to track the reactions to a stimuli or to detect the ongoing electrical impulses (brain waves). These are known as potentials associated to events. The EEG has great temporal resolution, which is a benefit, but it is insufficient for establishing three-dimensional spatial localization (Savoy, 2001). German psychiatrist Hans Berger is credited with discovering the EEG in 1929, according to Tudor & Tudor (2005). The EEG was initially used on July 6, 1929, during a neurosurgery procedure on a 17-year-old. This resulted in a significant leap in neuroscience.


EEG anomalies in psychopaths and non-psychopaths were compared in a research done in 2012 by Calzada-Reyes and colleagues. They employed 58 male violent criminals from a Havana City jail. The PCL-R exam revealed that 31 of the offenders (the experimental group) were psychopaths, whereas the other 28 were not psychopaths (control group). Each offender was given a questionnaire concerning their use of drugs and alcohol, the results of which are presented in the table below:

Table 1 displays environmental influences on the variables for the experimental and control groups (Calzada-Reyes et al., 2012).

This demonstrates that the experimental group (psychopaths) often consumes more alcohol and psychoactive substances. Furthermore, mistreatment occurred when 55 of the perpetrators were children (30 psychopaths and 25 non-psychopaths). All participants were advised to maintain their calm state throughout the continuous EEG recording in order to reduce movement-related signals.

The findings reveal that while the QEEG revealed greater levels of beta activity in the left parieto-temporal regions of the brain and the bilateral occipital areas in the psychopath group, the visual assessment of the EEG revealed no significant differences between the groups. LORETA was used to verify this. The psychopath group showed less alpha activity than the control group did in the left parieto-central and centro-temporal regions. This research supports the notion that neurodevelopmental problems are a contributing factor in the theory that psychopathy is caused by anomalies in the fronto-temporo-limbic system (Calzada-Reyes et al., 2012).

Functional MRI

Müller and colleagues utilised an fMRI in 2003 to examine how happy and negative pictures affected the activity of the brain in psychopaths. They utilised a control group of six healthy males without a history of neuropsychiatric problems as their subjects. Six male psychopathic patients from a high-security mental health hospital made up the experimental group. In order to evaluate the emotional process, images were employed. Examples of good things included ice cream, joyful couples, puppies, etc. Negative imagery included bones, injured humans, and angry animals/faces, whereas neutral pictures included books, structures, and silverware. To assess the contrast that is dependent on blood oxygen levels, a 1.5 Tesla MRI system with a 25-mT gradient system and a head coil was employed using the fMRI technique (BOLD).
According to the findings, pleasant pictures made psychopaths' bilateral activity of their fusiform cortex, parietal cortex, cerebellar hemispheres, temporal and precentral cortex, as well as their unilateral left-sided activation of their gyrus frontalis inferior, rise. Additionally, the medial frontal gyrus and medial temporal gyrus decreased unilaterally on the right side and bilaterally in the occipital brain. In the picture below, this (increased activation in blue and reduction in red).

Figure 1: A brain scan illustrating the variations in mechanisms behind happy emotion According to Müller et al. (2003), they depict the areas of interest where there is a higher level of activation (blue) compared to the control group (red).

The medial temporal gyrus, occipital, and parietal cortex all showed a bilateral increase in activity. Additionally, it was discovered bilaterally on the left side in the superior temporal gyrus and precentral brain. The anterior cingulate, the amygdala, and the inferior and medial frontal gyrus were all larger on the right side. On the picture below, this is shown in blue. The subgenual cingulate, the medial temporal gyrus, and the gyrus fusiformis all showed unilaterally decreased activity on the right side. Additionally, it was discovered unilaterally on the left side in the dorsal cingulate, the parahippocampal gyrus, and the lobulus paracentralis (Müller et al., 2003). This is shown in red.

Figure 2: A brain scan demonstrating the ways in which positive and negative emotions are processed differently in psychopaths. When compared to the control group (red), the regions of interest in psychopaths (blue) are more activated (Müller et al., 2003).

According to the study's findings, the stimuli caused both an increase and a decrease in the activity of the brain's emotional-related regions. Comparing these differences to the group of healthy controls revealed that they were considerably different. This suggests that neurodevelopment affects psychopathy in some way.

The Prefrontal Cortex in Psychopathy

The frontal lobe is in charge of cognition, planning, and decision-making.

Many scientists think that psychopathy is influenced by frontal brain injury. Phineas Gage was a well-known example of a person whose personality changed as a result of prefrontal brain injury (as mentioned earlier). He was reliable and trustworthy before the disaster. However, because of the injury to his prefrontal brain (PFC), he developed the psychopathy-related qualities of disrespect, unreliability, and impulsivity. Studies investigating the connection between prefrontal injury (mostly ventromedial and orbitofrontal) and a deficiency in social behaviour and decision-making have been conducted since this instance (Hajak et al., 2008).

Numerous studies have examined the PFC's grey matter organisation. Three different participant groups were used in one research by Yang et al.: 16 failed psychopaths (one or more convictions); 13 successful psychopaths (no convictions); and 23 non-psychopaths as a comparison group. When compared to successful psychopaths and the control group, it was shown that the failed psychopaths had a smaller PFC volume. However, when the PFC volume of the successful psychopaths and the control group were examined, there was no discernible difference. Yang and colleagues also looked at the regional cortical thickness in 32 healthy non-psychopathic people and 27 subjects who were psychopathic. They were matched in terms of age, gender, and drug usage. According to the findings, the PFC thickness was lower in the psychopathic group than in the control group. The right frontal and temporal cortices' grey matter was shown to be thinning. These findings were in line with the theory that psychopathy and grey matter volume are related. Ermer and colleagues conducted one of the biggest investigations in 2011. Voxel-based morphometry and multiple regression analysis were used to look at the association between the degree of psychopathy and the grey matter structure in 254 males from a jail. The outcomes revealed a poor connection between the PCL-R checklist and the volume/concentration of grey matter (Koenigs, 2012).

Laakso and associates looked at the relationship between psychopathy and prefrontal volume in 2002. It was discovered that those who exhibited antisocial behaviour had smaller left orbitofrontal, medial, and dorsolateral cortices. However, neither the level of education nor alcohol usage were accounted for. There were thus no discernible changes after these were controlled. This research contradicted the findings of prefrontal volume in psychopathy (Hajak et al., 2008).

In one research, reversal learning was matched to the dysfunctional ventromedial prefrontal cortex in kids with psychopathic tendencies. Children with oppositional defiant disorders (ODD) or attention-deficit/hyperactivity disorders (ADHD) exhibit more violent and antisocial behaviours. Some of these kids also exhibit psychotic characteristics including a lack of regret or shame. Reversal learning is the process through which a person learns to react to stimuli in order to get a reward. They must learn to react to new stimuli in order to get the reward since once the reaction is known, it is no longer rewarding. It is believed that those who exhibit psychopathic tendencies are unable to achieve this. It is proposed that the ventrolateral PFC reacts to events involving conflict after the dorsal medial PFC is engaged, and that lesions on the orbital and PFC are the source of this impairment. In children and adults who exhibit psychopathic tendencies, damage in the ventromedial PFC impairs reversal learning, according to recent research in neuroimaging and lesion data. The ventromedial PFC or the ventrolateral PFC was shown to be dysfunctional in children who display psychopathic tendencies, according to an analysis of fMRI data. Additionally, they looked at a group of kids with ADHD who lacked any indications of psychopathic qualities as well as a control group of healthy kids who lacked both ADHD and psychopathic features. The findings of this research indicate that children with psychopathic tendencies have anomalies in the ventromedial PFC. There was no indication that the ventrolateral or dorsomedial PFCs were dysfunctional (Finger et al., 2008). All except one of the studies listed point to a critical function for the prefrontal cortex in psychopathy.

The Amygdala in Psychopathy

Understanding the strong aggressiveness is crucial since the amygdala is involved in processing emotions. It is crucial for moral thinking, social connection, and rewarding learning as well (Yang et al., 2009).

The amygdala being damaged is another theory for why psychopathy occurs. Individuals may struggle to recognise distress signs in others or trigger fearful reactions as a consequence of the injury (Pardini et al., 2014).

One of the first research in this field examined the amygdala's localization of deformations in psychopaths. A portion of the 86 subjects, who were all from Los Angeles in California, had significant rates of psychopathy. The PCL-R exam was again used to confirm psychopathy. With a PCL-R score of 23 or above, the findings revealed that 27 of these people were psychopaths. A control group of 32 non-psychopaths with a score of 15 or less was employed. The amygdala was examined using MRI analysis. When psychopathic people were compared to the control group, it was shown that there was a reduction in the bilateral amygdala volume. The findings demonstrated that the basolateral, lateral, cortical, and central nuclei of the amygdala contained the majority of the decreases. According to this research, the amygdala is one of the fundamental characteristics of a psychopath. These findings are also in line with past investigations into amygdala lesions, which demonstrate that injury to the amygdala is a source of emotional deficits, which is a characteristic of psychopathy (Yang et al., 2009). Pardini and colleagues conducted more study on this in 2014. Male participants' reduced amygdala size were investigated to see if they had a history of aggressiveness or psychopathic tendencies as children. They also examined whether an increase in the likelihood of violent behaviour would result from the amygdala's volume being reduced. In a longitudinal research conducted in 1986–1987, 503 guys were first picked from the Pittsburgh Youth Study (PYS). Then, 56 of the 503 men were selected at the age of 26 and had histories of violence of different severity, including no violence, transitory significant violence, and chronic serious violence. Using automated segmentation, the size and level of hostility in the amygdala were studied. The findings revealed no discernible association between amygdala volume and the males categorised according to history of severe violence. However, the amygdala sizes were smaller in individuals who had shown greater violent behaviour and psychopathic tendencies between early adulthood and childhood. This indicated that males were more likely to perform violent acts in the future if their amygdala volumes were lower.

The volume of the amygdala and the characteristics of aggressiveness and psychopathic tendencies from infancy to adulthood were compared for the first time in this research.

A different research examines how psychopaths make moral judgements. It is thought that emotion influences moral judgement and stimulates the amygdala's activity. We investigated the association between the brain activity of psychopaths and moral issues using an fMRI. 17 volunteers from a group of people with varying degrees of psychopathy evaluated 10 circumstances using the following categories:

? moral personal - stirring the emotions (for example, should a baby be smothered to protect themselves and other people from a terrorist).

? moral impersonal - less sentimental (for example, should money found in a lost wallet be kept)

? non-moral (for example, what transport is best to take – bus or train).

On the PCL-R exam, the levels of psychopathy varied from 7.4 to 32, with 32 indicating a high level of psychopathy.

It was discovered that individuals with higher PCL-R exam scores had greater amygdala activity decrease during moral decision-making. The medial prefrontal cortex, posterior cingulate, and angular gyrus all showed decreased activity. This is in line with the theory that in psychopaths, the amygdala's normal function is compromised while making moral choices. It is evident in every characteristic of psychopathy, which strongly implies that amygdala anomalies may be a major factor in psychopathy (Glenn, Raine and Schug, 2009).

Dadds and associates looked at fear recognition in juvenile psychopathy in 2006. Both individuals with amygdala injury and psychopathy have the inability to recognise fear. This supports the hypothesis that anomalies in the amygdala are linked to psychopathy. This research investigated the possibility of treating fear recognition deficiencies in children with psychopathic tendencies. 33 boys between the ages of 8 and 15 participated in the first trial, while 65 boys between the ages of 9 and 17 participated in the second. Participants came from Sydney, Australia, schools. According to this research, failing to see the area around other people's eyes causes them to fail to recognise fear. By focusing on the area around the eyes, you may change this. One of the earliest studies to demonstrate this alteration was this one. It should be mentioned, nevertheless, that Richell and colleagues in 2003 discovered that people with psychopathic tendencies were able to recognise emotions on faces by looking at stimulus faces that included just the information from the eye area.

The Temporal Lobe in Psychopathy

The sensory input, language, and memory are all influenced by the temporal lobe. The hippocampus, which is important in short-term memory, is located in the medial temporal lobe. It's thought that aberrant linguistic abilities may be one factor contributing to psychopathy. According to research, semantic processing activities make psychopaths' impairment to language processes more obvious. According to one view, psychopathic people have trouble understanding abstract language. Since abstract words pertain to things like acts, feelings, and ideas, concrete words are those that can be understood by the five senses (touch, smell, sight, taste, and hearing). Event-related potential (ERP) data revealed that psychopaths were unable to discern between tangible and abstract terms, according to Kiehl et al. (1999). This revealed that the difficulty for psychopathic people to distinguish between the terms was due to the frontal-temporal lobes.

An fMRI was used in one research to look at temporal lobe deviations in criminal psychopaths. Eight male convicts with psychopathic tendencies were utilised, all from a maximum security facility in Canada. The PCL-R test was used to gauge the degree of psychopathy, with the control group failing to exhibit any psychopathic characteristics. Age, educational attainment, parental socioeconomic level, and drug usage in the six months before to the research were all comparable. The study's stimulus words were either concrete or abstract and lacked any evocative overtones. The findings supported the premise that psychopathic people processed abstract words much more slowly than a control group. When processing abstract phrases, the psychopathic experimental group had trouble engaging the right anterior superior temporal gyrus. These results agreed with earlier study findings (Kiehl et al 2004).

In a research conducted in 2008 by Hajak and colleagues, this was further supported. 17 psychopathic subjects and 17 healthy controls were contrasted. Each subject was a guy of a comparable age who had not used drugs during the previous six months before the trial. When compared to the control group, psychopaths have less grey matter in the right and left superior temporal gyrus, according to voxel-based morphometry (VBM). The illustration below illustrates this:

Figure 3: When compared to a control group, it can be shown that psychopaths have different anatomical characteristics in their grey matter. Yellow represents the grey matter loss. glass brain B: a considerable loss of grey matter in both premotor cortex and temporal lobes. C: Bilaterally significant loss of grey matter in the temporal lobes. D: A notable loss of grey matter in the right middle cingulate gyrus (Hajak et al., 2008).

The temporal cortex was shown to have a crucial role in psychopathy.

Other behavioural investigations have looked at temporal lobe epilepsy patients who exhibit certain psychotic characteristics. The patients' animosity decreased and their social interactions improved after the defective temporal lobe was removed. This supports the hypothesis that anomalies in the medial and anterior temporal lobes play a key role in psychopathy, in line with prior findings (Kiehl et al., 2006). In a 2001 research, the relationship between psychopathy and the temporal lobe's posterior hippocampus is investigated. The study had 18 male volunteers who had all received convictions for serious crimes. They were all alcohol dependant and had at least one personality problem. This research used an MRI, and the findings revealed a poor association between the PCL-R scores and the volumes in the hippocampus. This shows that the hippocampus and psychopathy may be related, and it is also thought that the findings of this research may provide some support for the somatic marker idea (Laakso et al., 2001).

Corpus Callosum in Psychopathy

The axons that make up the corpus callosum link the left and right hemispheres of the brain. It has white matter, which enables communication between the various brain areas (Mooshagian, 2008). It is thought that certain aggressive and antisocial criminals have functional abnormalities in the corpus callosum, notwithstanding the paucity of study on the anatomy of the corpus callosum and its role in psychopathy. Of one research, the white matter and corpus callosum structures in psychopaths and a control group were compared. Additionally, it examines if the aberrations are linked to an emotional deficiency, which is a characteristic of psychopathic behaviour. The study included 15 psychopaths as participants and 25 as controls. They were chosen from five temporary work agencies, enabling a demographic match between the experimental group and the control group. An MRI was used to calculate the corpus callosum's white matter length, thickness, and volume. The findings revealed that the experimental group's white matter volume increased by 22.6% when compared to the control group. Additionally, the experimental group's white matter length was 6.9% longer and 15.3% thinner than the control groups. Furthermore, the aberrant callosal anatomy persisted even after drug misuse was under control. This implies that neurodevelopment may have a role in psychopathy (Raine et al., 2003). Transcranial magnetic stimulation (TMS) has also been utilised in recent research to investigate the relationship between aggressiveness and the corpus callosum. The TMS analyses the signal transmission to determine how well the two hemispheres are connected. Psychopaths were shown to have stronger signals between the right and left sides of the brain than a control group. It shows that psychopathic people with violent inclinations have a diminished reaction in the right cerebral hemisphere (Schutter and Harmon-Jones, 2013). These findings point to a connection between aggressiveness and the corpus callosum, which may be related to psychopathy as aggression is one of its characteristics.

Biochemistry of Psychopathy

Biochemistry may also be a factor in the development of psychopathy. These are the chemical reactions that take place in living things. Monoamine oxidase (MAO) is thought to be connected to psychopathy. Through blood platelets, this substance is extensively dispersed throughout the human body. Several studies have linked reduced platelet MAO to personality problems, however the connection is still ambiguous (Lidberg et al., 1985). Lidberg's research looks at platelet MAO activity in psychopaths. He tested 37 male patients from a Stockholm forensic psychiatric clinic between the ages of 23 and 62 versus a control group. At the same time each day, blood samples were drawn, and the presence of MAO was then examined. The findings revealed that the psychopathic group had a very low level of MAO activity, which was to be anticipated given that psychopathy is associated with personality problems.

The prefrontal cortex's glucose metabolism was the subject of another investigation. Comparisons were made between a control group of individuals with similar age and gender and 22 participants who were charged with murder but pled not guilty due to insanity. The findings demonstrated that the prefrontal cortex's glucose metabolism was considerably lower in the killers. Although further research is needed, there were no discernible alterations in the posterior frontal and temporal lobes, suggesting that it is localised to the prefrontal cortex (Raine et al., 1994).


Numerous experts think that abnormalities in the brain are a significant factor in psychopathy. Most researchers have reached the same conclusion after looking at structural and functional problems, mostly in the frontal lobe, amygdala, temporal lobe, and corpus callosum. Future research needs to make numerous advancements in our understanding of the relationship between neurodevelopmental abnormalities and psychopathy.

According to the studies included in this review, the prefrontal-temporo-limbic system has a structural and functional role in the development of psychopathy. Overall, it was shown that psychopaths had less grey matter in the prefrontal and temporal cortex when compared to a control group. Numerous studies have shown that the amygdala may have a role in the development of psychopathy. According to the findings, psychopaths have decreased amygdala basolateral, lateral, cortical, and central nuclei. Other research in this area revealed that the amygdala's dysfunction, which causes issues with emotion processing, may possibly be a factor. This is because one of the characteristics of psychopathy is impaired emotion processing. Although it is thought that the corpus callosum is related to psychopathy, further study is necessary. However, it is important to note that the findings of the study conducted by Raine and colleagues in 2003 imply that there may be some participation, and this might serve as a foundation for further investigation in this area. His research looks at the white matter's structure, and although this calls for additional study, it may be crucial to look at its function and, if any, any associations with psychopathy. Studies on the temporal lobe point to a crucial function for it. When a group of psychopaths were exposed to concrete and abstract phrases in comparison to a control group, it was discovered that there were functional deficiencies. When processing abstract phrases, they had difficulty engaging the right anterior superior temporal gyrus. Additionally, this was in line with a prior research by Kiehl et al.A few research have been done on the biochemistry of psychopathy, including ones on monoamine oxidase. There may be a link between them, according to some. However, this also needs further study, and it hasn't been the subject of many current studies since 1980. The investigations tend to imply that psychopathy is caused by a number of interconnected brain abnormalities rather than by a single neurobiological factor. According to Weber et al. (2008), both psychopathic adults and children with psychopathic features have amygdala abnormalities, although it is thought that only adults have orbitofrontal cortex dysfunction while performing activities. This may be evidence of the emergence of psychopaths, but it might simply be the result of drug misuse, which is sometimes connected to psychopathy. Overall, the evidence points to a link between psychopathy and brain abnormalities.

When examining neurobiological studies of psychopathy, it is crucial to take into account a few methodological issues. The definition of a psychopath is one of the key issues. Most research use Hare's PCL-R exam to assess this. Researchers do utilise a variety of cutoff scores, however. For psychopaths, the conventional cutoff score is beyond 30, whereas for non-psychopaths, it is under 20. As opposed to Kiehl et al. (2004), who used a cut-off score of 28 or higher, Yang et al. (2009) used a cut-off score of 23 or higher. According to Koenigs, this is because it is difficult to locate people with high psychopathy scores exceeding 30 in a forensic context (2012). Another methodological problem is to be able to assemble a control group that matches the experimental group in age, education, and history of drug misuse. It could be beneficial to establish a little lower score as a cut off for everyone to follow in order to prevent any objections. These significant elements may have an impact on the structure and operation of the brain. This proved crucial in the research conducted in 2002 by Laakso and colleagues, as an example. In the first trial, neither alcohol intake nor education level were taken into account. The theory was disproved once these effects were taken into account since there were no significant correlations between antisocial behaviour and prefrontal volume. However, there are several studies that take into account factors like age, education, and past drug misuse, and the findings indicate a connection between brain abnormalities and psychopathy. As a result, even if Laakso and colleagues' theory was disproved, there is still a link between brain abnormalities and psychopathy.

Additionally, in several research it is unknown whether a control group was utilised, and in the majority of the studies, the groups had tiny sample sizes. This makes it possible to compare the findings to those of other research that used a comparable number of people, but it also casts some question on whether they are substantial enough to back up the ideas. However, it is challenging to obtain a big enough cohort for study since it is thought that just 1% of people are psychopaths. As a result, it is known whether the functional abnormalities are caused by psychopathy or are just the result of physiological alterations brought on by incarceration. Many of these research are based on failed psychopaths (those who have been convicted).

Additionally, there is not a lot of study on female psychopathy, and the most of the studies that have been identified have looked at men. Researchers' presumption that psychopathic traits may be transferred to females may be to blame for this. Although it is thought that girls are less likely to develop psychopathy than men are, it is unclear how this is shown behaviorally. Additionally, there haven't been many research on how men and women acquire psychopathy and if there are any notable distinctions (Wynn, Hoiseth and Pettersen, 2012). Future research may be able to look into brain anomalies in female psychopaths, but given how uncommon it is in women, it may be challenging.


In summary, the investigations have shown a link between psychopathy and anomalies in the brain, namely in the frontal and temporal cortex, amygdala, and corpus callosum (the prefrontal-temporo-limbic circuit). These deviations might be functional or structural. There are also some theories that the anomalies are chemical in nature, which have received some research backing. To draw a definitive, general judgement on whether psychopaths have defective brains or not, however, further study is required. It's also important to note that people with other mental illnesses, including schizophrenia, also have impairments in similar brain areas. The hypothesis that psychopaths have aberrant brains is supported by the investigations to far, but further study is required for a definitive response.


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