SAN FRANCISCO— George Patterson, co-founder of Menta Capital LLC, said on Tuesday that he has left the San Francisco-based quantitative hedge fund firm.

Patterson started Menta in late 2006 with Asriel Levin and Laurent Dubois. The three were formerly portfolio managers at Barclays Global Investors, a unit of British bank Barclays PLC (UK:BARC: news, chart, profile) , which is one of the largest "quant" investment firms in the world. See related story.

Patterson said he left for personal reasons and remains an investor in Menta. He’s now looking for new opportunities in the investment-management business, but said he may consider positions outside of the $2 trillion hedge fund industry. Menta has roughly $750 million in assets, he said.

Stock markets have been extremely volatile in recent weeks, which can hurt quant hedge funds. These types of funds use computer models to generate trading ideas. Some use a market-neutral approach, which aims to balance long positions with short trades. Others are so-called statistical arbitrage funds, which analyze historical relationships between related securities and trade when those relationships get out of whack.

Many of these funds were hit hard in the summer as forced selling by some managers disrupted such historical relationships. See full story.

Some quant hedge funds may be experiencing similar difficulties again, experts said Friday. See full story.

"January was not a pretty month," Patterson said in an interview. "I don’t know the exact numbers because I’m not involved directly with Menta anymore. It was a tough month, but that was not just for Menta, it was across the board."

Dubois, a managing member of Menta, didn’t immediately return a phone call seeking comment on Tuesday.