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PROBLEM: Out at the fringes of sleep research, small studies have shown that applying a "gentle electric current" can ease the brain into deep sleep, improving sleep quality and increasing overnight memory retention. But the potential therapy has yet to gain popular appeal, probably because the whole sticking electrodes to your head thing just screams "don't try this at home." (There are, of course, companies that are trying to sell you on trying it at home, but you'll need to find upwards of $600 and a doctor willing to write you a note.)

METHODOLOGY: German researchers recruited 11 subjects to spend two nights in their sleep lab. During one night, as the participants approached deep sleep, the researchers played sounds ("pink noise") that were synchronized to their brain rhythms. As a control, no sounds were played the other night.

In addition, the participants were shown 120 pairs of words each night before going to bed. First thing in the morning, they were tested to see how many of the pairs they remembered.

RESULTS: While it didn't cause them to experience more deep sleep cycles, the pink noise appeared to prolong deep sleep and to increase the size of the subject's brain waves during that period, as evinced by their EEGs.