This week's broadcast, with guest host Lee Cowan, features Faith Salie's cover story on a "Quiet Revolution" by introverts. Also: Cowan profiles comedian Louie Anderson, who won an Emmy playing a family matriarch on "Baskets"; Anthony Mason interviews Foo Fighters frontman Dave Grohl; Mark Strassmann visits the "witness trees" at Gettysburg National Military Park; and Jane Pauley profiles actor Michael J. Fox, who has launched an online study to help researchers develop new therapies for Parkinson's disease.