Developing an objective indicator of fatigue: An alternative mobile version of the Psychomotor Vigilance Task (m-PVT)

Approximately 20% of the working population report symptoms of feeling fatigued at work. The aim of the study was to investigate whether an alternative mobile version of the ‘gold standard’ Psychomotor Vigilance Task (PVT) could be used to provide an objective indicator of fatigue in staff working in applied safety critical settings such as train driving, hospital staffs, emergency services, law enforcements, etc., using different mobile devices. 26 participants mean age 20 years completed a 25-min reaction time study using an alternative mobile version of the Psychomotor Vigilance Task (m-PVT) that was implemented on either an Apple iPhone 6s Plus or a Samsung Galaxy Tab 4. Participants attended two sessions: a morning and an afternoon session held on two consecutive days counterbalanced. It was found that the iPhone 6s Plus generated both mean speed responses (1/RTs) and mean reaction times (RTs) that were comparable to those observed in the literature while the Galaxy Tab 4 generated significantly lower 1/RTs and slower RTs than those found with the iPhone 6s Plus. Furthermore, it was also found that the iPhone 6s Plus was sensitive enough to detect lower mean speed of responses (1/RTs) and significantly slower mean reaction times (RTs) after 10-min on the m-PVT. In contrast, it was also found that the Galaxy Tab 4 generated mean number of lapses that were significant after 5-min on the m-PVT. These findings seem to indicate that the m-PVT could be used to provide an objective indicator of fatigue in staff working in applied safety critical settings such as train driving, hospital staffs, emergency services, law enforcements, etc

Wrist-Worn Psychomotor Vigilance Task Device Validation Study

Prepared for: Naval Advanced Medical Development Program; Naval Medical Research Center; 503 Robert Grant Avenue, Silver Spring, MD 20910Collecting reliable human performance data in military operational environments is an ongoing challenge. A major issue of concern is identifying systems that can capture human performance metrics in a reliable and valid manner in the field. One task that has been used extensively in the laboratory - and more recently in field settings - is the Psychomotor Vigilance Test (PVT). Since 2008 the PVT has been included as a feature on a wrist-worn actigraph (AMI, Inc.), thereby enabling researchers to easily administer the PVT in the field. The current project has three aims, a) to validate the 3-minute PVT which is currently embedded in the AMI actigraph, b) to explore the utility of other devices for field use, and c) to provide recommendations for the collection of PVT data in the military operational environments. In our studies, we found that when the screen backlight is illuminated, the results of the 3-minute PVT on the AMI actigraph are comparable to those from the laptop PVT. These findings demonstrate that the 3-minute PVT on the AMI actigraph is a valid alternative to the 3-minute laptop-based PVT for field assessment. Given the widespread use of hand-held devices with a touch screen interface, we also tested a PVT application on a representative touch screen device. Our findings were disappointing, showing that the hand-held touch screen PVT system was not comparable to the validated PVT. In particular, the touch screen PVT introduced a large constant bias as well as a proportional bias that decreased the range of response speed. These findings raised the question of what the appropriate user interface should be for a field-grade PVT system. Herein, we present a method we have developed and refined over multiple years to prepare PVT data collected in field setting for analysis. This method reduces bias due to missing data and artifacts from external disturbances by assessing the quality of the PVT data on three levels: the raw response level, the aggregated (trial) level, and the participant level. In brief, our experience of collecting PVT data, combined with findings from this current 3 year effort, suggests that when administering the PVT in field settings, it is best if the PVT is embedded in a wearable device such as the AMI device. While other types of devices (e.g., smartphones, iPods, tablets, etc.) can be used for PVT administration, they have important constraints which should be taken into consideration.Naval Medical Research Center Advanced Medical Development ProgramNaval Advanced Medical Development Program; Naval Medical Research CenterApproved for public release; distribution is unlimited

Reduced Neurobehavioral Impairment from Sleep Deprivation in Older Adults: Contribution of Adenosinergic Mechanisms

A night without sleep is followed by enhanced sleepiness, increased low-frequency activity in the waking EEG, and reduced vigilant attention. The magnitude of these changes is highly variable among healthy individuals. Findings in young men of low and high subjective caffeine sensitivity suggest that adenosinergic mechanisms contribute to inter-individual differences in sleep deprivation-induced changes in EEG theta activity, as well as optimal performance on the psychomotor vigilance task (PVT). In comparison to young subjects, healthy adults of older age typically feel less sleepy after sleep deprivation, and show fewer response lapses, and faster reaction times on the PVT, especially in the morning after the night without sleep. We hypothesized that age-related changes in adenosine signal transmission underlie reduced vulnerability to sleep deprivation in older individuals. To test this hypothesis, the combined effects of prolonged wakefulness and the adenosine receptor antagonist, caffeine, on an antero-posterior power gradient in EEG theta activity and PVT performance were analyzed in healthy older and caffeine-insensitive and -sensitive young men. The results show that age-related differences in sleep loss-induced changes in brain rhythmic activity and neurobehavioral functions are mirrored in young individuals of low and high sensitivity to the stimulant effects of caffeine. Moreover, the effects of sleep deprivation and caffeine on regional theta power and vigilant attention are inversely correlated across older and young age groups. Genetic variants of the adenosine A2A receptor gene contribute to individual differences in neurobehavioral performance in rested and sleep deprived state, and modulate the actions of caffeine in wakefulness and sleep. Based upon this evidence, we propose that age-related differences in A2A receptor-mediated signal transduction could be involved in age-related changes in the vulnerability to acute sleep deprivation

Changes in performance and bio-mathematical model performance predictions during 45 days of sleep restriction in a simulated space mission

Lunar habitation and exploration of space beyond low-Earth orbit will require small crews to live in isolation and confinement while maintaining a high level of performance with limited support from mission control. Astronauts only achieve approximately 6 h of sleep per night, but few studies have linked sleep deficiency in space to performance impairment. We studied crewmembers over 45 days during a simulated space mission that included 5 h of sleep opportunity on weekdays and 8 h of sleep on weekends to characterize changes in performance on the psychomotor vigilance task (PVT) and subjective fatigue ratings. We further evaluated how well bio-mathematical models designed to predict performance changes due to sleep loss compared to objective performance. We studied 20 individuals during five missions and found that objective performance, but not subjective fatigue, declined from the beginning to the end of the mission. We found that bio-mathematical models were able to predict average changes across the mission but were less sensitive at predicting individual-level performance. Our findings suggest that sleep should be prioritized in lunar crews to minimize the potential for performance errors. Bio-mathematical models may be useful for aiding crews in schedule design but not for individual-level fitness-for-duty decisions

The circadian rhythm as a temporal frame to detect phase differences in physiological and psychological functions

Human physiological and psychological functions are under control of the circadian clock. The purpose of this study was to analyze the potential effects of circadian modulation on cognitive performances, and to quantify the phase relationships between physiological and psychological functions. For the experiment, 18 Chinese female participants were recruited who were studying in Munich. In an isolated room with constant light conditions the subjects participated in the experiment from 7:00 to 23:00. They gave their subjective evaluations on sleepiness, satiety, and mood; their body temperature, grip strength, hear rate, blood pressure, and salivary cortisol were measured. A cognitive battery was used for objective testing, including a two-flash fusion task, psychomotor vigilance task, a Go/No-go task, a finger tapping task, and a temporal reproduction task. Within the concept of temporal perception, the tested domains were classified into a tens-millisecond to a thousands-millisecond time window. This study showed the significant influence of circadian rhythm on temporal perceptions for all tasks. Clustering different functions suggested that temporal perception is different in the morning and in the afternoon. The diurnal rhythms of biomarkers and subjective and objective functions indicated the regulatory role of the endogenous circadian clock. The different phase relationships of functions provide hints for underlying neural processes.Die physiologischen und psychologischen Funktionen des Menschen stehen unter der Kontrolle der zirkadianen Uhr. Ziel dieser Studie war es, die potenziellen Auswirkungen der zirkadianen Modulation auf kognitive Leistungen zu analysieren, und die Phasenbeziehungen zwischen physiologischen und psychologischen Funktionen zu quantifizieren. Für das Experiment wurden 18 chinesische Teilnehmerinnen mittleren Alters rekrutiert, die in München studieren, um in einem isolierten Raum mit konstanter Beleuchtung den tageszeitlichen Verlauf von Funktionen wischen 7:00 und 23:00 Uhr zu messen. Die Teilnehmerinnen gaben unter anderem subjektive Bewertungen zu Schläfrigkeit, Sättigung und Stimmung ab. Außerdem wurden Körpertemperatur, Griffstärke, Herzfrequenz, Blutdruck und das Speichelcortisol gemessen. Des Weiteren wurde eine kognitive Batterie eingesetzt mit Aufgaben zur Prüfung der zeitlichen Fusion, der psychomotorischen Vigilanz, der zentralen Hemmung mit einer Go/No-Go-Aufgabe, des persönlichen Tempos und der zeitlichen Reproduktion. Im Hinblick auf die zeitliche Wahrnehmung wurden Zeitfenster von zehn bis tausend Millisekunden eingeteilt; dieser Bereich der Studie zeigte den signifikanten Einfluss des zirkadianen Rhythmus auf die zeitliche Wahrnehmung in allen diesen Zeitbereichen. Diese unterschiedlichen Muster deuten darauf hin, dass die zeitliche Wahrnehmung am Morgen und am Nachmittag unterschiedlich ist. Die Tagesrhythmen der Biomarker sowie der subjektiven und objektiven Funktionen zeigen die regulierende Rolle der endogenen circadianen Uhr. Die verschiedenen Phasenbeziehungen der Funktionen erlauben Hinweise auf zu Grunde liegende neuronale Prozesse

Neurophysiological vigilance characterisation and assessment: Laboratory and realistic validations involving professional air traffic controllers

Vigilance degradation usually causes significant performance decrement. It is also considered the major factor causing the out-of-the-loop phenomenon (OOTL) occurrence. OOTL is strongly related to a high level of automation in operative contexts such as the Air Traffic Management (ATM), and it could lead to a negative impact on the Air Traffic Controllers’ (ATCOs) engagement. As a consequence, being able to monitor the ATCOs’ vigilance would be very important to prevent risky situations. In this context, the present study aimed to characterise and assess the vigilance level by using electroencephalographic (EEG) measures. The first study, involving 13 participants in laboratory settings allowed to find out the neurophysiological features mostly related to vigilance decrements. Those results were also confirmed under realistic ATM settings recruiting 10 professional ATCOs. The results demonstrated that (i) there was a significant performance decrement related to vigilance reduction; (ii) there were no substantial differences between the identified neurophysiological features in controlled and ecological settings, and the EEG-channel configuration defined in laboratory was able to discriminate and classify vigilance changes in ATCOs’ vigilance with high accuracy (up to 84%); (iii) the derived two EEG-channel configuration was able to assess vigilance variations reporting only slight accuracy reduction

Sleep quality influences subsequent motor skill acquisition

While the influence of sleep on motor memory consolidation has been extensively investigated, its relation to initial skill acquisition is less well understood. The purpose of the present study was to investigate the influence of sleep quality and quantity on subsequent motor skill acquisition in young adults without sleep disorders. Fifty-five healthy adults (mean age = 23.8 years; 34 women) wore actigraph wristbands for 4 nights, which provided data on sleep patterns before the experiment, and then returned to the laboratory to engage in a motor sequence learning task (explicit 5-item finger sequence tapping task). Indicators of sleep quality and quantity were then regressed on a measure of motor skill acquisition (Gains Within Training, GWT). Wake After Sleep Onset (WASO; i.e., the total amount of time the participants spent awake after falling asleep) was significantly and negatively related to GWT. This effect was not because of general arousal level, which was measured immediately before the motor task. Conversely, there was no relationship between GWT and sleep duration or self-reported sleep quality. These results indicate that sleep quality, as assessed by WASO and objectively measured with actigraphy before the motor task, significantly impacts motor skill acquisition in young healthy adults without sleep disorders. (PsycINFO Database Record. (c) 2016 APA, all rights reserved).Accepted manuscrip