What makes us who we are? Is it our background that creates our identities? Or our families, where we lived, how we were brought up and educated, the jobs we've held? Yes, all of the above, but more fundamental than any of these is our brain.

This is never more evident than if we lose even a single one of our cognitive abilities. People who develop a brain disorder can find that their identity, their sense of self, can undergo dramatic changes. Through the stories of seven of his patients, acclaimed Oxford University neurologist Masud Husain shows us how our brains create our identity, how that identity can be changed, and sometimes even be restored.

Among the people we encounter is a man who ran out of words, a woman who stopped caring what others thought of her and another who, losing her memory, started to believe she was having an affair with the man who was really her husband.