Ad agency holding company Interpublic Group has formed a new media buying and planning unit called Mediabrands, shuffling some senior posts and bringing in execs from other companies as a result. Mediabrands will bring together all the various media shops under IPG, allowing greater sharing of resources—especially the back office operations—across agencies. Anticipating questions about the long-rumored combination of all its media agencies into one, IPG says that the media units will still remain distinct. To a lesser point, an IPG spokesperson told me, the move reflects the changing landscape between traditional and digital media. Exec changes include:

-- Nick Brien, CEO of IPG’s Universal-McCann, who takes that title with him as head of the new unit. Brien will manage global media networks UM and Initiative, IPG’s centralized negotiation entity Magna and media barter group Magna Trading, dedicated Johnson & Johnson agency J3 and diversified agencies NSA, OSI and Wahlstrom, as well as marketing accountability shop MAP and IPG’s Emerging Media Lab.

-- Matt Seiler leaves his post as president and CEO of PHD North America, a media shop owned by rival holding company Omnicom Group, to take on the CEO post at UM.

-- The second newcomer to IPG is Michael Hudes, who will head diversified media services and strategic development for Mediabrands. Previously, Hudes was the global director of digital media for ClearChannel (NYSE: CCU). Release

• Industry Moves: Initiative USA Names Spengler President; Cohen Presides Over Worldwide Innovation