Tokyo's key Nikkei index closed lower in cautious trade Thursday ahead of the Jackson Hole conference of global financial authorities and Friday's press conference by Japan's prime minister. The benchmark Nikkei 225 index fell 0.35 percent, or 82.00 points, to end at 23,208.86, while the broader Topix index lost 0.53 percent, or 8.59 points, to 1,615.89. nf/sah/fox