A rare opportunity to hear Dr. Sanjay Gupta unplugged — removed from the rush of breaking news.  In my recent conversation with the neurosurgeon and CNN chief medical correspondent, we discuss the latest science on keeping your brain sharp — well into old age;  how he weighs risk and reward; the remarkable story of the brain surgery he performed during a sandstorm in Iraq to save the life of a Marine — when the proper tools were not available.  We also discuss his latest book on the pandemic - World War C -including lessons for after the pandemic.