NEW YORK, Sept 24 (Reuters) - U.S. stock futures were slightly higher in volatile trading at the start of the overnight session following comments by Federal Reserve Chair Janet Yellen and news that she was receiving medical attention after the speech in which she struggled to finish her last lines.
A spokesman for the University of Massachusetts at Amherst, where the speech was held, said later that Yellen was expected to resume her schedule Thursday and attend a planned dinner.
Among other comments, Yellen said she expects the Fed to raise interest rates later this year.
S&P 500 e-mini futures were down 0.2 percent at the start of the overnight session but later turned slightly higher and were last up 0.4 percent.
Investors had been cautious on Thursday ahead of the speech, awaiting clues on the timing for the first rate hike in almost a decade. (Reporting by Caroline Valetkevitch; Editing by David Gregorio)