Psychopathy is a personality construct and is evaluated by the use of the PCL-R by a mental health professional with specific training and certification. Not only the psychopath has certain personality features and can be considered a particularly severe
case of ASPD, with narcissistic traits such as lack of empathy and a grandiose sense of self-worth, but they also have distinct brain functioning patterns. Their frontal a pre-frontal cortex is much less active than normal, as well as some lymbic system elements
such as the amygdala. To have a better notion, you should check the image bellow.