Yang and Raine (2009) provided a meta-analytic evaluation of 43 studies, dating from 1994 through 2007, involving brain imaging in antisocial, violent and psychopathic individuals. These studies reported significant impairments in the prefrontal cortex of antisocial individuals; specifically, impairments were shown in the right orbitofrontal cortex, right anterior cingulate cortex, and left dorsolateral prefrontal cortex. The purpose of this meta-analysis was to evaluate recent studies (2009-present) that assessed differences in functional imaging variables in the prefrontal cortex and their relationship to antisocial or psychopathic behavior.
Why is it important to study the relationship between brain physiology and psychopathy? First, it is necessary to find the cause of psychopathy in order to understand, diagnose, and formulate a program of treatment for these individuals. Second, the burgeoning field of brain imaging technology provides a more expansive look into the human brain in search of a biological basis for psychopathy. Third, the implications of these studies could advance the understanding of other related neuropsychiatric conditions such as sociopathic behavior, bipolar conditions, or aggressive tendency. Finally, it may be argued that, much like those with severe mental disabilities, the physiological determinants which cause psychopathy may diminish an individual's responsibility for criminal conduct (Hagerty, 2010).
The term psychopath has been described by Hare (1999) as a "self-centered, callous, and remorseless person profoundly lacking in empathy and the ability to form warm emotional relationships with others, a person who functions without the restraints of conscience" (p. 2). Psychopathy is considered a personality disorder and was specifically included in the Diagnostic and Statistical Manual of Mental Disorders (DSM) until it was conceptually merged in the DSM-III with antisocial personality disorder (APD). Researchers have criticized the DSM-IV's definition of antisocial personality disorder for its overemphasis on behavioral outcomes such as criminality and under-emphasis of the core personality features such as affective deficits (Hare, 1999). Recent changes in the DSM-V, however, seem to address this issue by listing the criteria for APD as a person having "significant impairments in the personality functioning manifest by: impairments in both self-functioning and interpersonal functioning as well as pathological personality traits in the domains of antagonism and disinhibition." (pp. 659-663). Unlike previous versions, this criterion takes into consideration the personality traits that are present in a psychopathic individual in addition to the antisocial behaviors.
Hare and Harpur (1991), provided the most widely used scale to measure psychopathy, the Hare Psychopathy Checklist--Revised (PCL-R). The PCL-R is a diagnostic tool created in the early 1990s for use in clinical, legal, and research settings to determine an individuals' level of psychopathic tendencies. The PCL-R assesses the following traits: "glib and superficial charm, exaggerated grandiosity, need for stimulation, pathological lying, cunning and manipulativeness, lack of remorse or guilt; shallow affect (superficial emotional responsiveness), callousness and lack of empathy, parasitic lifestyle, poor behavioral controls, sexual promiscuity, early behavior problems, lack of realistic long-term goals, impulsivity, failure to accept responsibility for own actions, many short-term marital relationships, juvenile delinquency, revocation of conditional release, and criminal versatility" (Hare & Harpur, 1991). Each of these characteristics is scored on a 3-point scale by an experienced rater during a semi-structured interview; additional materials are extracted from the subjects' institutional records. A score of 0 indicates that the item definitely does not describe the person; 1 that it describes somewhat or only in a limited sense; and 2 that it definitely does describe the individual. …