Nikkei opened 0.58 percent lower Thursday as the yen firmed versus the dollar, triggering by Federal Reserve Chairman Ben Bernanke\'s comment that its accommodative monetary policy would be needed for the foreseeable future. At 9:15 a.m., the 225-issue Nikkei Stock Average was down 84.03 points, or 0.58 percent, from Wednesday at 14,332.57. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was down 8.47 points, or 0.71 percent, at 1, 186.73.