Behavioral Biology

For all the technology applied to warfare today, the outcomes of armed conflicts continue to be largely determined by the mental acuity and alertness of warfighters, many of whom are confronted with limited opportunities for adequate sleep and rest.

Under the leadership of Thomas Balkin, Ph.D, a past chairman of the board of the National Sleep Foundation, the Behavioral Biology branch investigates and develops methods for optimizing warfighter alertness, performance, and resilience. Its primary research mission – using data gathered at the center’s specially designed sleep laboratories, in the field, and from sophisticated models and simulation tools – is to identify the role of sleep in facilitating resilience to, and recovery from, exposure to sleep loss and other combat-related stressors.

“WRAIR sleep researchers were the ones to show,” said Bliese, “that physiologically, the parts of the brain that were really shutting down after sleep loss were the parts in the prefrontal cortex that had to do with a lot of the higher-order decision making. This is common knowledge today, but practically speaking it was an important innovation, because we could show these images to senior leaders within the military and others, and say: ‘This isn’t an issue of motivation or effort. The vigilance and performance deficits that result from sleep loss have a physiological basis:  the part of the brain that performs higher-order mental tasks like decision-making literally “shuts down” with sleep loss.  So if you deprive soldiers of sleep, you’re going to have a lot of negative consequences.’”

The center has been renowned for its sleep research since the early 1960s, when WRAIR scientists were the first to demonstrate that microsleeps (0.5-2.0 second lapses in wakefulness) account for some, but not all, of the cognitive performance deficits that characterize sleep deprivation; that a wide variety of mental abilities are affected by sleep loss; and that mental processing “speed” is generally affected more than “accuracy” by sleep loss. In the 1970s, recognizing the need for a wear-and-forget objective measure of sleepiness that could be used to measure sleep in  the military operational environment, WRAIR sleep researchers invented the wrist actigraph – a wristwatch-like device that provides sleep/wake data based on wrist movement measurements.  (Wrist actigraphs are now commercially available from a number of manufacturers, and widely used by sleep researchers and clinicians across the world.) In the 1980s and early 1990s, emphasis was placed on determining the sleep and performance effects of a variety of pharmacological agents – both sleep inducers (benzodiazepine agonists) and vigilance enhancers (e.g., modafinil, caffeine) – studies with implications for fatigue management in military operational environments. One result of this work was development of a caffeinated chewing gum product, which is currently provided as part of the military’s “First Strike Rations.”  With the advent of advanced functional brain imaging technologies in the 1990s and 2000s, WRAIR sleep researchers (with collaborators from NIH and John Hopkins University) performed groundbreaking research that characterized the changes in regional brain activity during sleep loss and sleep, showing that  (a) sleep deprivation primarily affects prefrontal cortical regions (constituting the physiological basis of cognitive deficits manifested during sleep loss); (b) although REM (dreaming) sleep is generally characterized by brain activity levels comparable to those seen during wakefulness, activity in the prefrontal cortex is depressed during REM (thus explaining the bizarre nature of dreams); and (c) reestablishment of conscious awareness after sleep is primarily a function of subcortical activation – full reactivation of the prefrontal cortex takes 10 to 20 minutes of continuous wakefulness.

“WRAIR sleep researchers were the ones to show,” said Bliese, “that physiologically, the parts of the brain that were really shutting down after sleep loss were the parts in the prefrontal cortex that had to do with a lot of the higher-order decision making. This is common knowledge today, but practically speaking it was an important innovation, because we could show these images to senior leaders within the military and others, and say: ‘This isn’t an issue of motivation or effort. The vigilance and performance deficits that result from sleep loss have a physiological basis:  the part of the brain that performs higher-order mental tasks like decision-making literally “shuts down” with sleep loss.  So if you deprive soldiers of sleep, you’re going to have a lot of negative consequences.’”

Building on these findings, the center’s Behavioral Biology researchers have developed algorithmic models that predict a soldier’s ability to perform cognitive tasks, based on their recent sleep history and their internal, circadian rhythm. “Being able to quantify the relationship between sleep deprivation and cognitive performance is a significant step,” said Bliese. “They’ve developed a series of models. If individuals go into the laboratory and are restricted to three to five hours of sleep a night, and they do this repeatedly, building cumulative sleep restriction, our researchers can accurately model the decline in performance.”

This algorithm has now been approved by the FAA and adopted by commercial airlines and others for use as a decision aid for developing optimal work/rest schedules (e.g., of aircrew, shiftworkers, and others).  Commercial entities have also licensed the government patents generated by Behavioral Biology scientists to incorporate the algorithm directly into wrist actigraphs, to optimize the utility of these devices for fatigue management at the level of the individual service member. “I could see something like this having a huge cultural impact in the Army, or in other work organizations,” said Bliese, “because if you’re in a highly demanding organization and you go to your boss and say: ‘Hey, I’m tired,’ your boss may say: ‘Just suck it up.’ But if you say to your boss: ‘Listen, I’m tired – and look, here’s my estimated cognitive performance,’ and you press the button and show him it’s at 58 percent, that’s going to have a much bigger impact.”

“I could see something like this having a huge cultural impact in the Army, or in other work organizations,” said Bliese, “because if you’re in a highly demanding organization and you go to your boss and say: ‘Hey, I’m tired,’ your boss may say: ‘Just suck it up.’ But if you say to your boss: ‘Listen, I’m tired – and look, here’s my estimated cognitive performance,’ and you press the button and show him it’s at 58 percent, that’s going to have a much bigger impact.”

Of course, service members are among several occupational groups for whom some periods of sleep deprivation are unavoidable, and another goal of the Behavioral Biology directorate is to help them through these periods without impairment. The center’s three-pronged fatigue management system (FMS) includes, in addition to monitoring sleep and alertness and modeling performance, the use of effective interventions – both pharmacological and non-pharmacological – to facilitate sleep and alertness as needed.

These interventions can be as simple as the targeted use of stimulants such as caffeine, which, if ingested, typically takes effect in 20 minutes, allowing time for a restorative nap before waking alert. The center has also tested a caffeinated chewing gum known as Stay Alert (now Military Energy Gum) that served as a quick and safe method of improving alertness and performance on mental and physical tasks, such as marksmanship.

A recent and ongoing area of research conducted by the directorate’s researchers is in the area of “sleep banking” – i.e., the finding that individuals can reduce sleep-related performance impairments during sleep loss by previously extending their time in bed. “In our group’s study,” said Bliese, “one group of subjects came to our lab for a week and extended their nightly time in bed to 10 hours.  They weren’t sleeping that whole time, of course, but it did extend their sleep time – and another group stayed on their typical sleep schedule [i.e., about 7-7.5 hours time in bed].” Both groups then went through a weeklong period of sleep restriction, sleeping only three hours per night, followed by a series of tasks of varying complexity.

“The results were like night and day,” Bliese said, “Those who’d ‘banked’ some sleep prior to sleep restriction were better able to maintain cognitive performance – and perhaps just as importantly, they also recovered from the sleep restriction much faster when subsequently allowed to resume their normal sleeping schedule.”

“The results were like night and day,” Bliese said, “Those who’d ‘banked’ some sleep prior to sleep restriction were better able to maintain cognitive performance – and perhaps just as importantly, they also recovered from the sleep restriction much faster when subsequently allowed to resume their normal sleeping schedule.”

“Until recently, the scientific sleep community dismissed the notion that there was any benefit whatsoever to extending nightly sleep duration beyond eight hours. Such ‘extra’ sleep was considered a waste – sort of like consuming more calories than are needed to satisfy daily energy requirements,” said Balkin. “But it turns out that this ‘extra’ sleep is stored and ‘released’ when it is needed during subsequent sleep restriction  – just like the energy from extra calories is stored as fat and released during subsequent food restriction.”  The study – which earned its lead investigator, Dr. Tracy Rupp, the National Sleep Foundation Young Investigator Award – suggests that if people can fill up their sleep coffers, they will be better equipped to deal with the challenges of sleep loss when they need to.

Currently, this group is focused on determining how sleep banking works, the potential benefits of non-pharmacological “slow wave sleep enhancement” – interventions that might increase the recuperative efficiency of sleep; and sleep-related strategies to enhance resilience to, and recovery from, mTBI events and psychological stress.