D. Brain Structure and Function
Whereas earlier biological theories considered the brain to be an organ with various areas of specialized function, modern theories recognize that the brain is a complex organism. Some areas of the brain are associated with specific functions (e.g., speech and vision), but all areas of the brain work together, and a problem or event in one area inevitably affects other areas. Although our understanding of the brain’s structure and function has significantly advanced, we still know little about the relationship between the brain and many behaviors, such as those related to crime. In addition, we know little about how the environment affects the brain’s structure and function.
The frontal lobe and the temporal lobe are two parts of the brain examined by researchers interested in criminal behavior. The frontal lobe is responsible for regulating and inhibiting behaviors, and the temporal lobe is responsible for emotionality, subjective consciousness, and responses to environmental stimuli.
Tools to evaluate brain structure, brain function, and behavior rely on sophisticated medical equipment and measurements, such as electroencephalography, computed tomography, magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography. These devices have been used by researchers to compare the brain structures and brain functions between criminal and noncriminal populations. In addition to providing images of structure, many of these technologies can track real-time changes in the brain’s neural activity before, during, and after exposure to physical or emotional stimuli.
Preliminary studies indicate that the brains of violent offenders and the brains of other individuals differ in both structure and function, but many of the studies have relied on very small sample sizes, which reduces the generalizability of these findings. Moreover, these studies also are plagued by questions of whether the brain causes the violence or whether violence results in changes to the brain. Evidence of structural or functional abnormalities in the brain has, however, resulted in the mitigation of criminal offenses, such as reducing charges of murder to manslaughter.
Studies of brain development have shown that early and chronic exposure to stress (e.g., abuse, neglect, violence) may cause physiological changes in the brain that impact the way a person responds to stress. Human brains under stress produce the hormone cortisol, which helps to return body functions to normal after a stressful event. However, repeated exposure to cortisol may result in decreased sensitivity to its effects and either contribute to criminality or contribute to a person’s acceptance of being victimized. In addition, this research is supported by studies on the brain development of children raised in high-stress environments (inner city, urban, high-crime areas) that found enhanced fight-or-flight impulses among these children.
A recent study by Diana Fishbein in 2003 concluded that behavioral problems may originate in the hypothalamic– pituitary–adrenal axis (HPA) that connects the brain to the adrenal glands, which regulate the production of important hormones. Fishbein claimed that increased levels of cortisol, produced in response to stressors, cause the HPA to shrink and become ineffective. An ineffective HPA depletes cortisol and results in the inability to regulate emotions and behavior. A dysfunctional HPA may be caused by stress in childhood that impedes its development, or it may be caused by damage later in life.