Watford have announced the signing of Italy international Marco Motta, subject to international clearance.
Mark Noble has signed a new deal with West Ham which will keep him at the club until the summer of 2020.
Midfielder Collison has been out of favour under Hammers boss Sam Allardyce this season.
He has made just three appearances and two of those were in the Capital One Cup. He came off the bench against Stoke last month for his only Premier League action.
The Wales international will now spend a month on loan on the Dorset coast.
Bournemouth boss Eddie Howe needs midfield cover with Richard Hughes suspended and Harry Arter and Shaun MacDonald both injured.