Daniel Reisel has spent a lot of time studying psychopaths (specifically murderers) in order to determine what neurological changes allow them to act without feeling or concern. Research indicates that psychopaths have a deficit in the amygdala, a brain region responsible for empathy. As a result, they lack the ability to feel for others. In this TED talk, Dr. Reisel discusses how this deficit may result from adverse experiences or negligent care during critical developmental periods.
Despite these critical periods, there is now evidence that our brains continue growing and changing, even in adulthood, through a process called neurogenesis (new neuron growth). As a result, Dr. Reisel believes that we can rehabilitate psychopaths through reforming corrections facilities so that they are allowed to develop and train their amygdala to make new connections while serving time.