Ideye Aide Brown opened the scoring for Sochaux before Nolan Roux equalised for Brest in the 38th minute.
Brest have 22 points from 13 games, one point ahead of Lille and Montpellier, who beat Toulouse 1-0 courtesy of an Olivier Giroud strike. Montpellier climbed from eighth to third.
After Sow's first-half hat-trick for Lille, Gervinho and Franck Beria completed a miserable day for Caen with their injury time strikes.
Ligue 1's top scorer Youssef El Arabi and Kandia Traore found the net for Caen but to little avail.
"We did everyting the wrong way tonight... I think we are just not up to the standard," Caen captain Nicolas Seube said on Orange Sport after the match.
Elsewhere, champions Marseille slipped to sixth place after settling for a 1-1 draw with Lens.
Stephane Mbia headed the ball home for Marseille in the sixth minute after a corner by playmaker Lucho Gonzalez but Eduardo scored the equaliser after the interval.
One week after their 2-1 defeat by arch rivals Paris Saint-Germain, the champions again dropped points and remain three points shy of the leaders albeit with a game in hand.
Bordeaux managed to snatch a 2-1 victory against Nancy after Geraldo Wendel scored a controversial goal in the dying seconds after the referee failed to see that he had handled the ball.
"There is a linesman, a referee, but they did not see it. It is part of the game," Nancy keeper Damien Gregorini said.
The match between Valenciennes and St Etienne was postponed because of bad weather in the north of France.
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