19 research outputs found
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Investigating Stochastic Resonance as a Countermeasure for Human Performance Decrement Associated With Spaceflight
NASA’s investigative team for human health and behavioral performance has deemed that the risk of adverse cognitive outcomes for future long duration space missions is high and requires mitigation. Current methods at addressing cognitive and human performance decrement may induce other negative effects or be prohibitive in deep space applications. Thus, new technologies, such as neuromodulation through non-invasive brain stimulation (NIBS), are currently countermeasures being investigated. Some of these techniques may also induce adverse cognitive outcomes or they may not integrate well into space habitat infrastructure. Therefore, this thesis investigates the use of sensory noise as a neuromodulation technique, through a phenomenon known as stochastic resonance.
Stochastic resonance occurs when noise resonates with a nonlinear signal, increasing that signal’s throughput and detectability. In human experimentation, additive sensory noise has been shown to improve perception and specific elements of cognition, but it is unclear whether these effects translate to improved performance in complex, operational tasks, such as those that astronauts conduct. Thus, this thesis research explores the utility of using sensory noise, specifically white noise added to the auditory and vestibular systems, for operational contexts and how it compares to other neuromodulation techniques.
First, this research builds upon the literature that implies sensory noise can be used to improve elements of cognition. Using the Cognition Test Battery, overall cognitive performance was assessed in subjects for seven separate cognitive domains while they did and did not receive noise stimulation. Additionally, a questionnaire was administered inquiring about subjective preference for working in noisy and quiet environments. Overall cognition was not affected by sensory noise in the broad population, but there appears to be an interaction between noise treatment and subject. When performance was correlated with preference to working in noisy environments, it was found that subjective affinity for working in noisy environments could predict whether additive noise improved cognition in a subject.
Second, this research investigated whether additive noise could be used to improve operator performance in a complex, lunar landing task. This task loaded on operational sub-dimensions related to flight, decision making, and perception identification. Again, no effects of sensory noise were found on operational performance for the broad population; however, there was a significant interaction between subject and noise treatment. Preference to working in noisy environments was not a predictor of noise susceptibility in this task though.
Third, this research explored the additive long-term effects of repetitive noise administration for an operational task to identify whether noise can improve skill acquisition. Additionally, it investigated the immediate and longitudinal effects of noise on behavioral health dimensions, such as sleep and mood. To assess this, subjects completed a lunar rover navigation task over the course of five days. In this between-subjects design, some groups received noise stimulation while completing the task while others did not. Subjective questionnaires were administered daily, before and after completing the navigation task. Learning occurred across all subjects; however, there was no significant difference in learning rate between stimulation groups. Additionally, there was no difference between groups in the behavioral health outcomes studied.
Finally, this research conducted a trade study to explore which brain stimulation technology may be the most appropriate for spaceflight given the spaceflight community’s interest in using NIBS technology as a spaceflight countermeasure. This trade study was applied to five brain stimulation techniques to determine which technology was the most effective at influencing human performance and integrating with the spaceflight vehicle. Transcranial electric stimulation appears to be the most promising stimulation technique based on the trade study’s criteria. Future work should identify how this technology interacts with performance in the spaceflight environment and why only certain individuals respond to sensory noise.</p
Galvanic vestibular stimulation produces cross-modal improvements in visual thresholds
Background: Stochastic resonance (SR) refers to a faint signal being enhanced
with the addition of white noise. Previous studies have found that vestibular
perceptual thresholds are lowered with noisy galvanic vestibular stimulation
(i.e., "in-channel" SR). Auditory white noise has been shown to improve tactile
and visual thresholds, suggesting "cross-modal" SR. Objective: We aimed to
study the cross-modal impact of noisy galvanic vestibular stimulation (nGVS)
(n=9 subjects) on visual and auditory thresholds. Methods: We measured auditory
and visual perceptual thresholds of human subjects across a swath of different
nGVS levels in order to determine if a subject-specific best nGVS level
elicited a reduction in thresholds as compared the no noise condition (sham).
Results: We found an 18% improvement in visual thresholds (p = 0.026). Among
the 7 of 9 subjects with reduced thresholds, the average improvement was 26%.
Subjects with higher (worse) visual thresholds with no stimulation (sham)
improved more than those with lower thresholds (p = 0.005). Auditory thresholds
were unchanged by vestibular stimulation. Conclusions: These results are the
first demonstration of cross-modal improvement with nGVS, indicating galvanic
vestibular white noise can produce cross-modal improvements in some sensory
channels, but not all.Comment: 15 pages, 7 figure
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A Standardized, Incremental Protocol to Increase Human Tolerance to the Cross-Coupled Illusion
Humans can adapt to the "Coriolis" cross-coupled illusion with repeated exposure, improving the tolerability of faster spin rates and enabling short-radius, intermittent centrifugation for artificial gravity implementation. This investigation assesses the criticality of personalization in acclimation to the cross-coupled illusion. We used the median stimulus sequence of our previous effective and tolerable personalized, threshold-based protocol to develop a standardized (non-personalized) approach. During each of 10, 25-minute sessions, the spin rate was incremented independent of whether each subject reported experiencing the cross-coupled illusion. In comparison to the previous personalized protocol, the standardized protocol resulted in significantly reduced acclimation to the cross-coupled illusion (17.7 RPM threshold for the personalized protocol versus 11.8 RPM threshold for the standardized) and generally increased motion sickness reports (average reporting of 1.08/20 (personalized) versus 1.98/20 (standardized)), on average. However, the lack of individualization also leads to significantly less variance in subjects' acclimation. These findings are critical for future missions that may require several astronauts to be acclimated concurrently, due to resource and time constraints. Assessing feasibility of fast spin rate, short-radius centrifugation is crucial for the future of artificial gravity implementation during spaceflight.</p
Training augmentation using additive sensory noise in a lunar rover navigation task
BackgroundThe uncertain environments of future space missions means that astronauts will need to acquire new skills rapidly; thus, a non-invasive method to enhance learning of complex tasks is desirable. Stochastic resonance (SR) is a phenomenon where adding noise improves the throughput of a weak signal. SR has been shown to improve perception and cognitive performance in certain individuals. However, the learning of operational tasks and behavioral health effects of repeated noise exposure aimed to elicit SR are unknown.ObjectiveWe evaluated the long-term impacts and acceptability of repeated auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS) on operational learning and behavioral health.MethodsSubjects (n = 24) participated in a time longitudinal experiment to access learning and behavioral health. Subjects were assigned to one of our four treatments: sham, AWN (55 dB SPL), nGVS (0.5 mA), and their combination to create a multi-modal SR (MMSR) condition. To assess the effects of additive noise on learning, these treatments were administered continuously during a lunar rover simulation in virtual reality. To assess behavioral health, subjects completed daily, subjective questionnaires related to their mood, sleep, stress, and their perceived acceptance of noise stimulation.ResultsWe found that subjects learned the lunar rover task over time, as shown by significantly lower power required for the rover to complete traverses (p < 0.005) and increased object identification accuracy in the environment (p = 0.05), but this was not influenced by additive SR noise (p = 0.58). We found no influence of noise on mood or stress following stimulation (p > 0.09). We found marginally significant longitudinal effects of noise on behavioral health (p = 0.06) as measured by strain and sleep. We found slight differences in stimulation acceptability between treatment groups, and notably nGVS was found to be more distracting than sham (p = 0.006).ConclusionOur results suggest that repeatedly administering sensory noise does not improve long-term operational learning performance or affect behavioral health. We also find that repetitive noise administration is acceptable in this context. While additive noise does not improve performance in this paradigm, if it were used for other contexts, it appears acceptable without negative longitudinal effects
Training augmentation using additive sensory noise in a lunar rover navigation task
Background The uncertain environments of future space missions means that astronauts will need to acquire new skills rapidly; thus, a non-invasive method to enhance learning of complex tasks is desirable. Stochastic resonance (SR) is a phenomenon where adding noise improves the throughput of a weak signal. SR has been shown to improve perception and cognitive performance in certain individuals. However, the learning of operational tasks and behavioral health effects of repeated noise exposure aimed to elicit SR are unknown. Objective We evaluated the long-term impacts and acceptability of repeated auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS) on operational learning and behavioral health.MethodsSubjects (n = 24) participated in a time longitudinal experiment to access learning and behavioral health. Subjects were assigned to one of our four treatments: sham, AWN (55 dB SPL), nGVS (0.5 mA), and their combination to create a multi-modal SR (MMSR) condition. To assess the effects of additive noise on learning, these treatments were administered continuously during a lunar rover simulation in virtual reality. To assess behavioral health, subjects completed daily, subjective questionnaires related to their mood, sleep, stress, and their perceived acceptance of noise stimulation. Results We found that subjects learned the lunar rover task over time, as shown by significantly lower power required for the rover to complete traverses (p 0.09). We found marginally significant longitudinal effects of noise on behavioral health (p = 0.06) as measured by strain and sleep. We found slight differences in stimulation acceptability between treatment groups, and notably nGVS was found to be more distracting than sham (p = 0.006). Conclusion Our results suggest that repeatedly administering sensory noise does not improve long-term operational learning performance or affect behavioral health. We also find that repetitive noise administration is acceptable in this context. While additive noise does not improve performance in this paradigm, if it were used for other contexts, it appears acceptable without negative longitudinal effects
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Tolerable Acclimation to the Cross-Coupled Illusion through a 10-day, Incremental, Personalized Protocol
Artificial gravity (AG) has the potential to provide a comprehensive countermeasure mitigating deleterious effects of microgravity. However, the cross-coupled "Coriolis" illusion has prevented using a more feasible and less costly short-radius centrifuge, as compared to large, slowly spinning systems.OBJECTIVEWe assessed tolerability of a personalized, incremental protocol to acclimate humans to the cross-coupled illusion, enabling faster spin rates.METHODSTen subjects were exposed to the illusion by performing roll head tilts while seated upright and spun about an Earth-vertical axis. The spin rate was incremented when head tilts did not subjectively elicit the illusion. Subjects completed one 25-minute session on each of 10 days.RESULTSThe spin rate at which subjects felt no cross-coupled illusion increased in all subjects from an average of 1.8 rotations per minute (RPM) (SD: ±0.9) at the beginning of the protocol to 17.7 RPM (SD: ±9.1) at the end. For off-axis centrifugation producing 1G at the rider's feet, this corresponds to a reduction in the required centrifuge diameter from 552.2 to 5.7 meters. Subjects reported no more than slight motion sickness.CONCLUSIONSAcclimation to the cross-coupled illusion, such as that accomplished here, is critical for feasibility of short-radius centrifugation for AG implementation.</p