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Biology 202
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Violence and the Brain

Jennifer Sabo

Is there a biological basis for violent behavior in the brain? Recent research links "neurological impairments and psychoses" to violent behavior (1). The "psychological effects" of brain damage and disease can cause the mind to lose touch with reality leading to criminal and violent behavior (1). As a result, free will may be deserted in an individual suffering from abnormalities and chemical imbalances in the brain (2). Consequently, legal issues arise because violent offenders with mental illnesses or brain injuries are not always to blame due to the biological nature of their diseases (2). However, violence in psychiatric and neurological patients can be prevented for the most part through medication and "social support services" (1).

A PBS video, "The Violent Mind" sparked my interest in the relationship between violence and the brain. The video presented several cases of violent assault which could be attributed to chemical imbalances in the brain (2). For example, the video illustrated the story of David Garabedian, a quiet passive man who murdered a customer of the lawn car company where David was an employee (2). David mixed lawn chemicals in their undiluted form which caused him to experience physical and mental changes in his body (2). Dr. David Bear, a physician from Vanderbuilt Medical School who looked into Davids case, claimed organophosphates in the insecticide poisoned the enzyme that clears away acetylcholine in the hypothalamus (2). Moreover, Dr. Bear stated that acetylcholine sends signals between the cells which coordinate aggression (2). This explains Davids reaction when the customer caught David urinating on her lawn (2). Before the urination episode, the action potentials of Davids nerve cells in the hypothalamus were at a low rate, but then he urinated due to the acetylcholine which caused the neurons to fire rapidly (2). According to Dr. Bear, the result was acetylcholine dropping at the synapse accounting for Davids overwhelming rage (2). As a consequence of Dr. Bears medical testimony, the murder case concerning David Garabedian was reopened for a trial (2).

Neurobiological research of violent and psychopathic behavior suggests there is a direct link between the enzyme, monoamine oxidase A (MAOA) and violence (3). In this particular study, H.G. Brunner associated aggression in males with "a mutation in the gene that codes for an enzyme, monoamine oxidase A (MAOA), which metabolizes the brain chemicals seratonin, dopamine, and norepinephrine" (3). In addition to Brunners research, Olivier Cases experimented with "MAOA-deficient" rat pups and adults (3). Cases data for the rat pups reported "abnormal behavior including trembling, fearfulness, and exaggerated startle reactions" (3). The adult rats displayed signs of intense aggression in which they attacked each other (3). Moreover, the pups had "elevated seratonin and norepinephrine" levels, whereas, the adults only had "elevated norepinephrine" levels (3). The rats also had "abnormalities in the somatosensory cortexes" (3). From this study, there is evidence that violence is biology-based. These findings, the researchers say, support the theory that the aggressive behavior of Brunners human subjects is a direct result of MAOA deficiency, rather than other genetic influences or psychosocial factors (3).

Furthermore, researchers have identified "antibodies for a Borna virus in up to a third of schizophrenic and obsessive-compulsive patients" (4). While the causes of most mental illnesses remain a mystery, surprising new research suggests that most cases of schizophrenia and other mental illnesses are associated with the Borna virus, an infectious agent that causes aggression, hyperactivity, and other behavioral disorders in animals (4). In addition, researcher, Liv Bode treated laboratory animals with a human strain of the Borna virus from "mood-disordered" patients (4). Consequently, the animals became aggressive and misbehaved (4).

The research of William J. Walsh indicates a relationship between copper and zinc concentrations and aggression (5). Blood samples were obtained from "135 assaultive males between the ages of 3 and 20, and 18 controls with no history of assaultive behavior" to analyze their serum copper and plasma zinc concentrations (5). The researchers found that the median copper/zinc ratio for the assaultive subjects was 1.40 compared to 1.02 for controls a statistically significant difference...Copper/zinc ratio [was] highest in subjects with a history of aggravated assaults followed, in descending order, by subjects who exhibited destructive rages, physical assaults, verbal assaults and normal behavior (5).

Anneliese Pontius, a Harvard psychiatrist, correlates seizures of the limbic system with violent crimes of 17 "loners" (6). She links the patterns of their crimes "with seizures, which often are preceded by auras, frequently cause irrational behavior and loss of normal bodily functions and are generally followed by a sense of disorientation" (6). According to Pontius, the seizures resulted from "limbic kindling" due to the loners lack of interpersonal relationships (6). Bottled up feelings, emotions, and memories were "triggered by people and objects" as stated by Pontius (6).

The research reviews and excerpt from the PBS video, "The Violent Mind", presented in this paper strongly support the evidence of a biological basis for violence in the brain.


1. "Violence and Mental Illness"

1. PBS video: Episode 8 "The Violent Mind"

1. "New Research Supports MAOA/Violence Link"

1. "Borna Virus Implicated in Mental Disorders"

1. "Copper, Zinc Levels Linked to Aggression"

1. "Controversial Theory Links Violence, Limbic "Kindling"

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