Have you ever noticed how your alarm clock sometimes wakes you up in a much more jarring fashion than usual? That's because on those occasions, you happen to be in one of the deeper states of sleep when it goes off. Not only is it more difficult to wake from these states, but people who do so also end up feeling less rejuvenated by their time in the sack. Scientists in India, however, think they may be on their way to designing an alarm clock that only wakes you up when the time is right.

There are five levels of brain activity that people vary between while sleeping, ranging from the relatively close-to-awake Stages 1 and 2, to the deep-sleeping Stages 3 and 4, followed by REM. Researchers at Jerusalem College of Engineering in Tamil Nadu would like to see a consumer alarm clock that monitors the user's brain activity, and waits until they're in Stage 1 or 2 before waking them.

In lab tests, they had volunteers set a wake-up time on a modified alarm clock, which was receiving output from electrodes that were wired to those peoples' scalps. The volunteers then proceeded to go to sleep. Ninety seconds before the set time arrived, the system started to monitor their brain activity. If they were in one of the first two stages within that period, the alarm would go off. If they stayed in the deeper stages, however, the clock would automatically go into "snooze" mode, and try again later.

While it's doubtful that anyone would want to wire themselves up every night, the Jerusalem College team envision a simpler commercial version of the system, in which users would wear a headband that wirelessly transmitted their sleep data. People could also use the system to obtain a timetable of their typical sleep pattern, so they could set their alarm for a time when they tended to be in one of the lighter sleep stages. Although this could result in their being woken considerably earlier than they would be otherwise, the scientists state that they would nonetheless end up being more refreshed and relaxed.

Other "bio alarm clocks" do already exist, such as the aXbo and the SleepTracker, although these monitor the user's sleep stages through an attachment on their wrist. Would a headband work better?

A paper on the research was recently published in the International Journal of Biomedical Engineering and Technology.