This study aims to assess whether slow wave sleep enhancement using SmartSleep technology benefits daytime cognitive performance during periods of chronic sleep restriction.
Adequate healthy sleep is essential in spaceflight to ensure that astronauts maintain a high level of cognitive performance capability and do so without undue stress. There is a need for a technology that can improve sleep quality in space and biologically maximize the performance benefits of limited sleep duration, without unduly affecting the ability of astronauts to awaken abruptly and respond to an in-flight emergency. Sleep slow waves support system and synaptic consolidation by promoting specific patterns of neuromodulatory and electric activities, and subjective sleep quality is related to the size and number of slow waves that occur nightly. This study will use SmartSleep (Philips) technology to determine what effect the device has on daytime cognitive performance after emergent awakenings from sleep in a chronic sleep restriction paradigm. The SmartSleep technology uses two small sensors in the headband to continuously detect the brain's slow wave sleep (delta/theta frequency) in real time, and a closed-loop algorithm customizes the timing and volume of tones to optimize the sleep pattern. Thus, the device uses "quiet audio tones" (sub-awareness) to increase slow waves, which can enhance sleep quality/depth, thereby enhancing subsequent waking cognitive performance without the unwanted sedating effects of medications on cognitive functions during emergency awakenings. Subjects will be in the laboratory for 7 days/6 nights. Night 1 will be an adaptation night with 8-hours time in bed. Nights 2-5 will consist of 5 hours time in bed, followed by night 6 of a recovery 10 hours time in bed. During nights 2-5, subjects will receive one of four stimulation modalities using the SmartSleep wearable device. Subjects will receive all four modalities in a randomized order: 1. Continuous Fixed Interval 2. Block 3. In-Phase Adjustable 4. Sham: No auditory stimulation while wearing the SmartSleep headband Cognitive performance testing and self-report surveys will be completed on a daily basis. A total of 12 healthy astronaut-like adults will be studied. Subjects will complete the 7-day study in groups of 4.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
TRIPLE
Enrollment
9
During the 4 nights of sleep restriction (5 hours time in bed), subjects will have one of the following SmartSleep stimulation modalities each night in a randomized order. All subjects will receive all 4 stimulation modalities: 1. Continuous Fixed Interval 2. Block 3. In-Phase Adjustable 4. Sham: No auditory stimulation while wearing the SmartSleep headband
During the 4 nights of sleep restriction (5 hours time in bed), subjects will have one of the following SmartSleep stimulation modalities each night in a randomized order. All subjects will receive all 4 stimulation modalities: 1. Continuous Fixed Interval 2. Block 3. In-Phase Adjustable 4. Sham: No auditory stimulation while wearing the SmartSleep headband
University of Pennsylvania
Philadelphia, Pennsylvania, United States
Psychomotor Vigilance Test-Brief (PVT-B)
The PVT is a simple reaction time test that requires participants to react, as quickly as possible, by pressing a response key as soon as a rolling number counter presented in a box in the center of the computer screen appears. The PVT is a validated and widely-used measure of vigilant attention that is sensitive to the effects of sleep loss. The primary outcome was the number of PVT lapses. The minimum number of PVT lapses is "0" and there is no maximum number of lapses, which are defined as response times \>355 ms. More PVT lapses indicates worse performance.
Time frame: Days 3-6
Slow-wave Activity
Total delta power measured during sleep
Time frame: Days 3-6
Digit Symbol Substitution Test (DSST)
The Digit Symbol Substitution Test (DSST) is a widely used measure of cognitive throughput and cognitive instability that is sensitive to the effects of sleep loss. The DSST was adapted from the Wechsler Adult Intelligence Scale. Participants are shown an array of symbols and with corresponding numbers on a keyboard. They are then presented the symbols one at a time in random order and must respond with the correct corresponding number as quickly as possible. The primary outcome was number correct and given the established practice effects on the DSST, this measure was corrected for practice effects. The DSST has a minimum of "0" correct responses and does not have a maximum; a higher number on the DSST represents better performance.
Time frame: Days 3-6
Descending Subtraction Task (DST)
The Descending Subtraction Test (DST) is a measure of working memory that is sensitive to the effects of sleep loss. The DST requires participants to mentally subtract numbers in a sequential fashion as quickly as possible. For example, if the starting number is 987, the participant subtracts nine from 987, with the difference being 978, the participant then subtracts eight from 978, and so on subtracting by seven, six, five, four, three, two, and one, from each difference at which point, and the participant then recycles the subtraction sequence beginning at nine again. The DST has a minimum of "0" correct responses and does not have a maximum; a higher number on the DST represents better performance. The primary outcome on the DST was Number correct.
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During the 4 nights of sleep restriction (5 hours time in bed), subjects will have one of the following SmartSleep stimulation modalities each night in a randomized order. All subjects will receive all 4 stimulation modalities: 1. Continuous Fixed Interval 2. Block 3. In-Phase Adjustable 4. Sham: No auditory stimulation while wearing the SmartSleep headband
Time frame: Days 3-6
Robotic On-Board Trainer (ROBoT) Task
The Robotic On-Board Trainer (ROBoT) task is NASA's platform for training astronauts to perform docking and grappling maneuvers using the Canada Arm. The system is based on highly realistic 3D simulations of the arm and associated physics. The ROBoT system involves a left-hand translational controller (x/y/z directions) and a right-hand rotational controller (pitch/roll/yaw), plus two laptop computer screens. Key performance metrics include: (i) docking position accuracy, (ii) docking orientation accuracy, (iii) total task time, and (iv) smoothness of approach trajectory, which are aggregated to generate the primary outcome, which is the mean weighted score . The weighted score ranges from 0 to 10 and a lower score indicates better performance.
Time frame: Days 3-6