For the first time, researchers have been able to study how a living brain interacts with Alzheimer’s proteins in real time -- and how parts of the brain are lost to the disease. The scientific breakthrough was made possible by tissue samples from living donors. CNN’s Isobel Yeung went inside the operating room to explain why one young man agreed to donate part of his brain. Stream the full story now on the CNN app.

Penn's Personal Update: Fighting Alzheimer's Journey