On the Mayo Clinic Radio podcast, Dr. Clifford Jack Jr., a radiologist at Mayo Clinic, explains the importance of a new Alzheimer's disease framework for improving research. Also on the podcast, Vivien Williams, medical reporter with the Mayo Clinic News Network, discusses "Health + Happiness With Mayo Clinic," the weekly program she co-hosts on NBC. And Dr. Thomas Brott, a neurologist at Mayo Clinic, looks back the advances he's seen in his 40 years of treating stroke.