What neurological abnormalities do people with psychopathy display? How might these abnormalities individually affect the expression of psychopathic behavior in the individual?
There have been several research studies that have looked at various neurological differences between individuals with psychopathy and non-psychopaths. Here are some common findings:

1.) Brain Structure: People who have Psychopathy tend to have smaller brains compared to those without it, particularly in areas related to emotional regulation and decision making. These structural differences may explain why they are often more aggressive, impulsive, and manipulative. Additionally, there is evidence to suggest that individuals with psychopathy exhibit decreased activity in brain regions responsible for empathy and remorse, which could contribute to their lack of remorse and guilt after engaging in criminal behaviors.
2.) Functioning of Neural Systems Associated With Emotion: People with Psychopathy appear to have altered functioning of neural systems associated with emotion. For example, they demonstrate reduced reactivity to stimuli that evoke negative emotions such as fear or anger, and increased responsivity to stimuli that trigger positive emotions like joy or gratitude. This suggests that they may have difficulty processing feelings of empathy and concern for others.
3.) Abnormalities In The Reward System: People with Psychopathy show impairments in the reward system, including diminished sensitivity to both social and physical rewards. They also seem to be less able to learn from experience, meaning that they continue to engage in harmful behaviors despite consequences.
4.) Changes In The Regulation Of Sleep And Wakefulness: There is evidence to indicate that people with Psychopathy have irregular sleep patterns and are often prone to nightmares and other symptoms of disturbed sleep. It is unclear if this is due to underlying biological factors, or if it is influenced by the chaotic lifestyle and frequent use of drugs and alcohol characteristic of this group.
5.) Altered Response To Distress: People with Psychopathy tend to respond to stress and trauma differently than those without it. For instance, they often display exaggerated startle reflexes and a lack of empathy towards others, which can lead to poor adaptation to stressful situations and increase vulnerability to mental health problems.

Overall, these studies suggest that there are distinct brain differences and functional impairments in individuals with Psychopathy that may contribute to the development and maintenance of their dangerous and antisocial behavior. However, further research is needed to fully understand the mechanisms involved and how they relate to specific symptom domains such as remorse and guilt.