After Wednesday's wild ride on Wall Street that ended on a down note, U.S. stocks rebounded a bit as investors braced for next week's Federal Reserve meeting on interest rates.

Most investors are still in wait-and-see mode ahead of the Fed's two-day meeting on Sept. 16-17 that could result in the first interest rate hike in almost a decade. Low rates, of course, have been cited as a key driver of the big stock market rally over the past 6 years.

The Dow Jones industrial average ended up 77 points, or 0.5%, after initially bouncing in and out of positive territory. Volatility continues to dominate the markets as the blue-chip index swung from a 172-point gain to a 239-point loss at the close Wednesday.

The Standard & Poor's 500 stock index gained up 0.5%, and the Nasdaq composite — which remains the only one of the three benchmarks in positive territory for 2015 — climbed 0.8%.

Investors remain uncertain as to what their next move should be, as there remains a lot of uncertainty as to whether the Fed opts to hike rates or hold off until later in the year. The Fed is dealing with crosscurrents, as the U.S. economy and labor market is gaining strength, which points to a coming hike. But on the flip side, market turbulence and financial instability due in part to China's slowing economy and weak stock market could give them pause.