Fresh Air with Terry Gross

Twenty years ago, when brain imaging made it possible for researchers to study the minds of violent criminals and compare them to the brain imaging of "normal" people, a whole new field of research — neurocriminology — opened up.

Adrian Raine was the first person to conduct a brain imaging study on murderers and has since continued to study the brains of violent criminals and psychopaths. His research has convinced him that while there is a social and environmental element to violent behavior, there's another side of the coin, and that side is biology.

When Marc Maron started his podcast "WTF with Marc Maron" out of his garage in September 2009, he was in a dark place: He was going through a divorce, his comedy career had hit a wall and — in his mid-40s — he didn't have a Plan B.

"I was at a place in my life where I had gotten very cynical," he tells Fresh Air's Terry Gross. "I had lost a lot of hope for my comedy and everything else, and I really feel that I was no longer able to really appreciate other people's stories. I had lost my ability to really kind of listen and enjoy the company of other people."