Neurophilosophy and free will - Patricia Churchland

Self-control can be undermined not just by things like extreme hunger and extreme exhaustion; it can be undermined by drugs. A huge effort around the world has gone into understanding the neurobiology of addiction and the main addictive chemicals, that people have studied, involve cocaine, heroin, nicotine, and alcohol. What is known now is that there are very specific physical changes in the reward system, in the basal ganglia, and it sometimes looks as though those very specific changes actually are quite permanent. So, understanding addiction is very closely related to understanding the nature of self-control.