The 21-year-old, who has appeared 82 times for Brighton, played five games on loan at Karl Robinson's Championship strugglers earlier this campaign.
The England Under-21 international is eligible for Saturday's FA Cup third-round match against Northampton Town.
"I've been here before, I know what the club is all about and I just can't wait to get started," he said.
Robinson added to the club website: "I felt he was a real success in his first spell with us earlier this season and this was highlighted when we looked back and saw he was the top of our attacking stats for a midfield player.
"When he was here before, Darren Potter wasn't fit and Samir Carruthers wasn't playing in central midfield and, as a group, this time around I'm sure they will offer good balance."
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Sean Corrigan, 31, was found at a flat in St Mary's Garden and later died in hospital.
Post mortem results indicated he may have died in suspicious circumstances.
Det Ch Insp Justyn Galloway said police believe Mr Corrigan may have been assaulted in the hours prior to his death.
"We are carrying out a full investigation into Sean's death," he said.
"We have examined CCTV footage and spoken to a number of witnesses. We will also be carrying out house to house enquiries in the area over the coming days.
"It is vital that we speak to anyone who may have more information in relation to Sean's movements that night and what happened in the apartment.
"I would urge the local community to help us ascertain what happened to Sean by coming forward with information. If you were in the area between 1am and lunchtime, if you saw any suspicious activity or if you have any other information about Sean's death which might assist us with our enquiries, then please get in touch."

In a speech marking the end of the Islamic holy month of Ramadan, he said Iran still had sharp differences with the US, above all over the Middle East.
Iran would continue to back Syria, Iraq, the Palestinians and "oppressed people" in Yemen and Bahrain, he said.
The deal on Iran's nuclear programme came after years of negotiations.
The agreement limits Iran's nuclear activities for at least 10 years in exchange for the gradual lifting of sanctions which have hampered the country's economy.
"Whether the [nuclear] deal is approved or disapproved, we will never stop supporting our friends in the region and the people of Palestine, Yemen, Syria, Iraq, Bahrain and Lebanon," Ayatollah Khamenei said.
"Even after this deal our policy towards the arrogant US will not change."
The supreme leader also denied that Iran was intending to create a nuclear bomb.
"The Americans say they stopped Iran from acquiring a nuclear weapon," he said in his speech at the Mosala mosque in Tehran.
"They know it's not true. We had a fatwa [religious ruling] declaring nuclear weapons to be religiously forbidden under Islamic law. It had nothing to do with the nuclear talks.
"We have repeatedly said we don't negotiate with the US on regional or international affairs; not even on bilateral issues.
"There are some exceptions like the nuclear programme that we negotiated with Americans to serve our interests... US policies in the region are diametrically opposed with Iran's policies."
The supreme leader said it was now necessary for Iranian politicians to scrutinise the nuclear agreement and make sure that Iran's national interests were being preserved.
Correspondents say that Ayatollah Khamenei's views are in contrast to the acclaim that the accord has received from President Hassan Rouhani and Foreign Minister Mohammad Javad Zarif.
MK Dons have re-signed Brighton & Hove Albion midfielder Jake Forster-Caskey on loan for the rest of the season.
[NEXT_CONCEPT]
Police have renewed their appeal for information on the first anniversary of the death of a man in west Belfast.
[NEXT_CONCEPT]
Iran's stance towards the "arrogant" US will not change despite the nuclear deal reached earlier this week, supreme leader Ayatollah Ali Khamenei has said.