The Netherlands international, who was dropped to the bench at Gladbach due to the form of Max Kruse, is determined to return to his best after moving to St James' Park
The 23-year-old made 45 appearances in two seasons at Gladbach after joining from Twente in 2012, but had not started a single Bundesliga match this campaign and failed to register a league goal.
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"I'm really motivated," De Jong told the club's official website. "The first half of the season hasn't been nice for me because I didn't play much.
"I just want to show my talent, score goals and be successful again. That is why I'm here. My goalscoring record in Holland was very good and hopefully I can show that here."
De Jong may make his Newcastle debut in Saturday's Tyne-Wear derby against Sunderland and says he cannot wait to experience the atmosphere.
"I know how big it is and I love playing in these massive matches. That is why I became a footballer," he continued.
"It's always nice to be involved in a game like that and I would love to play a part. We have to win it because otherwise I know we cannot walk around the streets of Newcastle."