GM Planworks, the unit of Publicis Groupe's Starcom MediaVest Group that handles the $3 billion-plus U.S. buying assignment for General Motors, has appointed an executive to oversee buying across all media platforms.

Mike Rosen will take over the new position of president of investment and activation, writes AdWeek (via MediaBuyerPlanner). Rosen joined Planworks last year after the agency won the GM assignment. Simultaneously, the shop promoted Mary Carpenter to the new post of president, strategy and operations; she will oversee planning for all General Motors divisions.

In recent months, several other shops, such as Omnicom Group's PHD, Interpublic Group's Initiative and Publicis Groupe's Starcom, have appointed executives to oversee buying across all media channels.