This episode's headline: Alzheimer's Disease; Advise & Consent; Low Gear. ANCHOR: JIM LEHRER; GUESTS: DAVID SNOWDON, University of Kentucky College of Medicine; MARCELLE MORRISON-BOGORAD, National Institute on Aging; REP. ZACH WAMP, [R] Tennessee; REP. GEORGE NETHERCUTT, [R] Washington; REP. CHAKA FATTAH, [D] Pennsylvania; REP. ZOE LOFGREN, [D] California; REP. HENRY BONILLA, [R] Texas; CORRESPONDENTS: CHARLAYNE HUNTER-GAULT; MARGARET WARNER; KWAME HOLMAN;