Neurology and Neurochemistry of Criminal/Antisocial Behavior

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Neurology and Neurochemistry of Criminal/Antisocial Behavior

 

Synonyms: brain; neurotransmitters; genetic expression

Introduction

Modern neuroscience has made significant and sometimes dramatic gains into understanding how the brain and central nervous system are implicated in a range of problematic, criminal, and addictive behaviors. Indeed, the growth of modern neuroscientific findings can only be described as explosive, with new discoveries being published almost daily. These findings are often produced by highly advanced technologies—technologies that, at a broad level, allow scientists to view the brain in action and under experimental conditions. This same technology also now allows scientists to directly measure brain cell activity and the strength and integrity of connections between brain cells. Never before in human history have scientists had these tools at their disposal.

Criminologists, once primarily wedded to sociological explanations of crime, are beginning to incorporate many of these findings into their understanding of the development of criminal conduct. They are also using these findings to understand the process of chemical addiction, how environmental experiences affect brain development, and how best to intervene with anti-social youths and adult criminals.

Apart from understanding brain structures and their functions, neuroscience has made tremendous progress in understanding how the chemicals in the brain, known as neurotransmitters, affect a range of personality traits and behaviors. This knowledge has led directly to the development of entire classes of psychopharmacological drugs. These drugs, known as selective-serotonin-reuptake-inhibitors (SSRI’s), have been used to effectively treat a range of mood and psychological disorders. New stimulants, too, have been created that help individuals better regulate their own conduct, including those diagnosed with attention-deficit-disorder. The point is, what neuroscience reveals to us about behavior, including criminal and imprudent behavior, may lead to better, more effective interventions.

Evolutionary and Developmental Background

The human brain is the most complex computational device known to exist. It controls all necessary life functions, takes over 20 years to fully mature, and allows human beings to exercise tremendous control over their behavior and their environment. The human brain is a marvel of complexity and has been subject to evolutionary selection pressures for at least 250,000 years. Anthropological and genetic evidence indicates that the human brain has undergone at least two key evolutionary changes. The first is a mutation in the ASPD gene. The ASPD gene codes for the abnormal spindle protein homolog protein. Around 6,000 years ago a new allele of the ASPD gene emerged, resulting in progressively larger brains across humans of European, Asian, and Middle Eastern decent. Brain size is positively correlated with intelligence and is thought to allow for increases in the number of neurons and the number of connections between neurons. Growth in brain size, however, was not uniform. The area of the brain responsible for all higher-order thought processes, known as the cerebral cortex, expanded to the point where today it accounts for 77 percent of total brain volume. Mutation in the ASPD gene corresponds with the advent of writing, agriculture, and science; although, it is unlikely to have directly caused them.

The second mutation also had a profound effect on human development and activity. Approximately 100,000 years ago a mutation in the FOXP2 gene occurred. Scientists believe that the mutation eventually allowed for the development of language. The mutation spread rapidly across ancestral populations, in large part because language provided early hominids a tremendous advantage in terms of survival. The area in the brain responsible for the production of language was discovered by a French physician, Paul Broca, and is known as Broca’s area. The area of the brain that allows individuals to understand language was named after German psychiatrist Carl Wernicke, and is known as Wernicke’s area. The development of language has allowed for tremendous advancements among human cultures. Interestingly, research has found that language deficiencies are positively correlated with antisocial behaviors.

Over 60 percent of our genes code for the structure and function of the brain. In terms of nuclear material, the brain is the most expensive organ to create. The average adult brain weighs between 1300 and 1400 grams, or about 3 pounds. Because brain development is under strong genetic control, several regions of the brain appear to be strongly heritable, including regions that allow individuals to control their emotions, to plan for the future, and to engage in self-control. The heritability of brain structure and functioning necessarily means that the traits and characteristics of biological parents, both physical and behavioral, are likely to be shared and expressed by their offspring. Numerous behavioral genetic studies show that most traits, including self-control, intelligence, and specific personality features are modestly to strongly heritable. Part of the reason for the correlation between parent and offspring behavior and traits is likely to be due to similar brain architecture and functioning. Criminologists have known since the 1800’s that criminal behavior and other social pathologies concentrate within some families and can show high degrees of inter-generational continuity.

The brain begins to develop almost immediately after conception. Research shows that during in-utero development the brain is forming over 250,000 connections per minute. While much of brain development is genetically controlled, evidence indicates that environmental factors can also be influential. Because the developing embryo is connected to the mother by the umbilical cord and placenta, maternal behavior can influence in-utero brain development of the fetus. Maternal nutritional intake is the clearest example. The fetus depends on receiving sufficient levels of nutrients from the mother. Insufficient nutritional intake can have devastating neurological consequences for the fetus. Moreover, maternal stress, and the accompanying release of stress hormones, has been shown to affect brain development of the fetus. While the brain of the developing fetus is protected by layers of fatty lipids, known as the blood-brain barrier, molecules from a variety of substances can pass from one side of the barrier into the developing central nervous system of the fetus. Maternal drug use and abuse, for example, has been found to potentially compromise the brain and central nervous system of the developing fetus. Cocaine molecules, as an example, easily pass across the blood-brain barrier. Moreover, lead (Pb), which can be stored in the bone of the mother, becomes bioavailable during pregnancy, passes through the blood-brain barrier, and may compromise healthy nervous system development. Prenatal lead exposure has been linked to a range of conduct problems, including delinquency in adolescence and criminal conduct in adulthood.

The rate of synaptogenesis, the creation of new nerve cell connections, corresponds directly to the increases in motor and cognitive abilities witnessed across childhood. Indeed, the brains of two year olds are about two-times as active as adult brains. Yet by late childhood the brain begins pruning unused and unnecessary synaptic connections. Reductions in the number of unnecessary connections eventually results in an increase in brain efficiency. The brain, in other words, does not have to use as much energy to do the same tasks in adulthood as it did in childhood. In part, this is due to the strengthening of connections through repetition; however, this is also due to the sculpting away of unused connections. While the sculpting begins in late childhood, it is accelerated during puberty when the brain undergoes a substantial period of reorganization. The onset of puberty also signals the myelination of the front part of the adolescent brain. Myelin is a fatty substance that will eventually cover axons. By covering axons in myelin the electrical impulse across the axon is accelerated by a factor of 10 over unmyelinated axons. The end result of these developmental changes is an energy efficient, highly integrated adult brain.

It is worth pointing out that although the brain undergoes substantial reorganization and pruning in the earlier stages of life, this does not mean that once one reaches adulthood the brain remains unchanged. On the contrary, the brain continues to change over time. Scientists do not yet know, however, how these changes are connected to criminal behavior.

 

Structures and Functions

The first part of the brain to develop is lower brain, which includes the brain stem and reticular activating system (RAS). The RAS contains a dense bundle of nerves that help direct sensory information to the correct parts of the brain. Psychologists have also linked variation in the RAS to certain personality characteristics, with some of these characteristics, such as neuroticism and extraversion, relating to offending. The lower brain controls all autonomic activities, such as breathing, that support basic life functions..............


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