Lisa Marshall, from University of Lubeck (Germany), and colleagues have discovered that by administering  interleukin-6 (IL-6), a molecule from the body's immune system, through the nose, the brain retains memories better during  the deep-sleep (REM) cycle.  The researchers recruited 17 healthy young men, each of whom spent two nights in sleep laboratory. On each night after reading either an emotional or neutral short story, they sprayed a fluid into their nostrils which contained either interleukin-6 or a placebo fluid. The subsequent sleep and brain electric activity was monitored throughout the night. The next morning subjects wrote down as many words as they could remember from each of the two stories. Those who received the dose of IL-6 could remember more words. The team comments that: "Here, we provide the first evidence that the immunoregulatory signal interleukin-6 plays a beneficial role in sleep-dependent formation of long-term memory in humans."