The former Watford midfielder could make his debut for the Bees against Oldham on Saturday and will now remain at Griffin Park until February 27.
Scott told his club's official website: "I'm delighted to have secured the services of Lionel.
"I know him well and he adds strength to a position that we've been looking at throughout the season.
"It helps us with building a squad when we can add players with Lionel's quality to it."
Source: Team Talk
Source: Team Talk