is there anything that's different about the brain of someone who's an addict versus someone else's brain? >> it's not the gross changes. it's how the cells communicate with each other that are changed. >> hurd showed me under the microscope. this is a healthy brain. lots of cells, lots of connections. >> beautiful, the branching, the communication is essential for every single thing we do. >> this is a brain on drugs. specifically, opioids. >> so one of the things you can see is that there's not that many networks. >> looks like a poorly populated neighborhood. >> exactly. >> this is what a brain disease looks like. opioids have damaged these receptors, the glutamate receptors in the prefrontal cortex of the brain making it harder to make decisions, use good judgment, making it harder to just say no. >> the craving is so prominent. it's so enormous that they can't stop themselves.