WRAIR Researchers Investigate How to Improve Alertness in Sleep-Deprived Warfighters

FORT DETRICK, Md. – A good night’s sleep is something that most people take for granted, but for Warfighters, chronic and acute sleep deprivation is an all-too-familiar part of their routine. Lack of sleep negatively impacts performance, which can lead to errors, injury and potentially even loss of life. To help overcome this problem, researchers at the U.S. Army Medical Research and Development Command’s Walter Reed Army Institute of Research are investigating ways to help Service Members get the most out of their sleep.

“Two thirds of Service Members do not sleep enough every night, a rate that’s twice as high as the civilian population,” explains Dr. Tracy Jill Doty, the chief of WRAIR’s Sleep Research Center. “Service Members are often in situations where they just can’t sleep for extended periods. There’s a need to have a tool that they could use in the field to help make short sleep opportunities more restorative. If they can only sleep for two hours, is there a way that we could make their sleep better?”

Doty and WRAIR senior sleep researcher Dr. John D. Hughes are investigating the use of gentle electrical pulses to stimulate the production of restorative brainwaves that occur during sleep. Preliminary evidence suggests that this approach helps boost the alertness and cognitive performance of Warfighters when they’re awake.

During deep sleep, the brain’s outer layer – called the cerebral cortex – buzzes with electrical activity that oscillates between 0.5 and 4.5 Hz, a much lower frequency than the waves that occur the brain when a person is awake. For years, researchers believed that the so-called “slow waves” associated with sleep were simply an indication of the brain returning to a default state in the absence of conscious thought. However, twenty years ago, a pair of researchers at the University of Wisconsin proposed a hypothesis that slow waves actually allow the brain’s neurons to restore their plasticity, which enables a person to respond more quickly and precisely to what’s happening around them when they’re awake.

Subsequent research has borne out the hypothesis that slow waves improve the brain’s performance. A 2006 study, for example, found that just 25 minutes of stimulation by slow waves in the first half-hour of a full night’s sleep improved the ability of test subjects to recall word pairs that they learned prior to going to sleep. These discoveries have opened up an entirely new field of neurological research – and suggested to Hughes that if restorative slow waves can be induced, rather than waiting for the brain to generate them itself, then people might be able to still experience the same benefits of a full night’s sleep even if they are only able to sleep for a few hours.

To test his hypothesis, Hughes designed a preliminary study in which undetectably weak positive electrical currents would be transmitted via sensors placed on the scalp – a technique called transcranial electrical stimulation, or TES – to induce the brain to start generating slow waves. The study participants were subjected to 46 hours of continuous sleep deprivation, during which researchers periodically assessed their performance with attention tests. The researchers found that the participants who had received TES during the two-hour sleep window performed significantly better during the subsequent sleep deprivation period than those who had not, suggesting that TES had enhanced the recuperative value of the short sleep period. Furthermore, the subjects who received TES recovered much more rapidly from their sleep deprivation once they were allowed to have a full night’s sleep again.

“We are not the first to use TES in sleep research, but I believe we are the first to have demonstrated that it has a positive effect on sleep restorative properties,” says Hughes.

Using the results of the preliminary study, the Sleep Research Center is now in the process of designing follow-up studies that will help them narrow down variables such as the optimal time during sleep to begin inducing slow wave production, the length of time that TES should be used to obtain the best results and the relative effectiveness of slow waves during longer and shorter periods of sleep. The team also plans to investigate whether a similar technique can be used during wakefulness to help reduce the biological urge to sleep, called sleep pressure.

Once those variables are better understood, Doty and Hughes believe, it will be possible to begin designing devices and techniques that Service Members can use in the field and in other environments where it is difficult to sleep, such as inside a noisy aircraft.

“We’re standing at the precipice of a neurotechnology revolution,” says Doty. “I think over the next five years we’re going to see commercial products using TES for all kinds of interesting applications. It’s an exciting time to be involved in this field.”