U.S. stocks rose on Wednesday, helped by a rebound in Apple shares, while expectations for a stronger economy and thus higher interest rates from the Federal Reserve boosted the dollar to a six-year high against the yen.

Yields on U.S. Treasuries continued their advance higher, with investors increasingly seeing momentum in the world's strongest economy prompting central bank action soon.

Worries over a vote for Scottish independence, scheduled for Sept. 18, spooked investors in Europe, where shares closed flat.

"There are so many factors that are supporting the dollar at the moment, mainly its better performance in the U.S., which will likely bring a more hawkish tone from the Fed," said Sireen Harajli, a foreign exchange strategist at Mizuho Corporate Bank in New York.

In addition, a study released on Monday from the San Francisco Fed showed investors underestimated the pace of eventual rate hikes, helping prompt gains in the dollar this week.

The greenback rose to a six-year high of 106.88 yen and was last up 0.65 percent, at 106.8700 yen.

The euro was last down 0.19 percent, at $1.2910, up from 14-month lows reached in the previous session.

The benchmark U.S. 10-year note yielded 2.543 percent, its highest in more than a month.

The Dow Jones industrial average .DJI rose 54.42 points, or 0.32 percent, to 17,068.29, theS&P 500 .SPX gained 7.31 points, or 0.37 percent, to 1,995.75 and the Nasdaq Composite.IXIC added 34.24 points, or 0.75 percent, to 4,586.52.

Apple (AAPL.O) shares jumped 3.1 percent to $101, and were the most actively traded on the Nasdaq, after several brokerages raised their price targets on the iPhone maker.

The FTSEurofirst 300 .FTEU3 index of top European shares ended 0.02 percent higher at 1,385.77 points. The benchmark index has erased all the gains spurred by the European Central Bank's moves last week to support the region's economy.

The MSCI world equity index .MIWD00000PUS, which tracks shares in 45 nations, rose 0.07 points or 0.02 percent, to 428.21.

Spot gold prices fell $6.55 or 0.52 percent, to $1,249.39 an ounce, pulled down by expectations of higher rates from the Fed. Gold futures GCcv1 were last up 0.14 percent, at $1,250.2 an ounce.

U.S. crude futures fell to a 16-month low and Brent to a 17-month low on rising supply and tepid demand as OPEC lowered projected demand for its crude and data showed U.S. refined product stocks jumped.

Brent crude LCOc1 was last down $0.96, or down 0.97 percent, at $98.2 a barrel. U.S. crude CLc1 was last down $1.02, or down 1.1 percent, at $91.73 per barrel.