The Wisconsin State Patrol is investigating a collision between motorcycles Thursday night in Columbia County that left one rider dead.  Troopers say two cycles were riding together on I-39 near the I-90/94/78 interchange when they made contact with each other on a curve and went into the ditch.  First responders performed C-P-R on an unresponsive 45-year-old man from Medford but he died at the scene.  The other rider was treated for minor injuries.  No names have been released.