CC130 pilot fatigue during re-supply missions to former Yugoslavia.

PURPOSE: Deployment of troops in foreign theaters requires a massive airlift capability. The fatigue encountered in such operations can be severe enough to pose a flight safety hazard. The current study documents sleep and the effect of fatigue on aircrew performance during re-supply missions in support of Canadian troops in Bosnia in 1996. METHODS: Ten routine re-supply missions from Trenton, Canada, to Zagreb, Croatia, were studied and involved 9 pilots and 9 co-pilots. To document their sleep hygiene, all pilots wore wrist actigraphs from approximately 5 d prior to the mission, until the mission was completed. Psychomotor performance was tested during the actual flights. Three psychomotor trials during the outbound transatlantic leg (Trenton to Lyneham, UK) were employed, one trial on the Lyneham-Zagreb-Lyneham leg, and three trials on the return transatlantic leg from Lyneham to Trenton. RESULTS: The amount of daily sleep during the 3-d period prior to the mission steadily decreased from an average of 8 h 40 min per day to 6 h 30 min (p < 0.001). During the missions, the worst night of sleep occurred during the second night overseas. During both transatlantic legs, there were significant decrements in the subjective ratings of alertness (p < 0.001), and increases in physical (p < 0.001) and mental fatigue (p < 0.001). Performance on the logical reasoning task as well as the multitask showed probable fatigue effects during the outbound leg of the missions. CONCLUSIONS: Our transport pilots showed a pattern of progressively decreasing sleep. Self-rated scores for alertness, mental and physical fatigue, indicate a deterioration of alertness, and an increase in fatigue throughout the long transatlantic flights.

Melatonin and zopiclone as pharmacologic aids to facilitate crew rest.

PURPOSE: In response to mission imperatives, transport aircrews must often sleep at inappropriate circadian times resulting in inadequate sleep. This study was undertaken to determine whether either melatonin or zopiclone could facilitate early circadian sleep, and to assess whether either of these medications would result in a psychomotor performance decrement which would preclude their use in aircrew. METHOD: Thirteen subjects from DCIEM completed a double-blind cross-over protocol. All subjects were assessed for psychomotor performance during 3 drug conditions (placebo, 10 mg melatonin, and 7.5 mg zopiclone), which were separated by one week. Each of these conditions involved 2 nights of sleep, back-to-back, with the first night being a normal circadian control sleep (23:00 h bedtime, arising at 06:45 h), and the second night being an early circadian drug sleep (drugs at 16:45 h, 17:00 h bedtime, arising at 23:45 h). All subjects were tested for psychomotor performance, on both nights of each of the 3 drug conditions, pre- and post-sleep. Further, during the early circadian drug night, all subjects were tested every hour after arising at 23:45 h (24:00 h until 07:00 h. At the beginning of each psychomotor test session, subjects were asked for their subjective levels of sleepiness and fatigue. RESULTS: Relative to placebo (339.5 min) the subjects slept more on melatonin (370.2 min, p < 0.01), and zopiclone (373.3 min, p < 0.01). Performance in serial reaction time (SRT) task (p < 0.001), logical reasoning task (LRT) (p < 0.001), serial subtraction task (SST) (p < 0.02), and Multitask (MT) (p < 0.03) were impaired for all 3 drug conditions immediately on awakening, compared with pre-sleep performance, as a result of a sleep-inertia effect. With respect to the subjective data, sleep inertia effects were evident for sleepiness (p < 0.001), mental fatigue (p < 0.002), and physical fatigue (p < 0.05). For SRT, LRT, and SST, performance recovered to pre-sleep levels within 1.25 h of awakening, and for MT recovery occurred 2.25 h after awakening. There were no differences in performance or subjective measures between placebo, melatonin and zopiclone. CONCLUSIONS: Both zopiclone and melatonin improved sleep relative to placebo. After sleep inertia, performance recovered to pre-sleep levels for all tasks and was sustained at that level throughout the balance of the testing period. There was no impact of melatonin or zopiclone on performance measures compared with placebo.

On the utility of experiential cross-training for team decision-making under time stress.

This study investigated the effectiveness of experiential cross-training in a team context for team decision-making under time stress in a simulated naval surveillance task. It was hypothesized that teams whose members explicitly experience all team positions will perform better under time pressure due to a better shared Team Interaction Model (Cannon-Bowers et al. 1993). In addition, it was posited that experiential cross-training would reduce the negative effect of member reconfiguration that can occur in certain military situations. Three groups of teams participated in this study (cross-trained, reconfigured and control). The experiment involved three team training sessions, followed by three time-stressed exercise sessions. During training, one group of teams was cross-trained (CT) by asking each member to perform an entire session at each of the three team positions. Member reconfiguration (where each member was shifted to another's position) was unexpectedly introduced at the first of the exercise sessions for the CT group and for another group (reconfigured) that had not been cross-trained. A third (control) group was neither cross-trained nor reconfigured. During training, the performance of non-CT teams improved more quickly than that of CT teams. During the exercise, the CT group did not achieve the level of performance of the control teams. The immediate effect of team member reconfiguration was to degrade performance significantly for the non-CT teams, but not for CT teams. The findings are discussed in terms of the multiple mental models' view of team performance (Cannon-Bowers et al. 1993) and the authors discuss the relative utility of cross-training when overall training time is fixed.

Self-monitoring cognitive performance during sleep deprivation: effects of modafinil, d-amphetamine and placebo.

Self-monitoring refers to the ability to assess accurately one's own performance in a specific environment. The present study investigated the effects of the stimulating drugs modafinil (300 mg) and d-amphetamine (20 mg) on the ability to self-monitor cognitive performance during 64 h of sleep deprivation (SD) and sustained mental work. Two cognitive tasks were investigated: a visual (perceptual) judgement task and a complex mental addition task. Subjects in the placebo condition displayed marked circadian and SD effects on cognitive task performance but their self-monitoring was substantively undisturbed by SD. Subjects performing under the influence of d-amphetamine likewise displayed highly proficient self-monitoring throughout the SD period. In contrast, modafinil had a disruptive effect on self-monitoring, inducing a reliable 'overconfidence' effect (i.e. an overestimation of actual cognitive performance), which was particularly marked 2-4 h post-dose. Although modafinil has proven to be a safe and effective countermeasure to the effects of extensive SD on cognitive task performance, we encourage a more comprehensive understanding of the relation between its subjective and performance enhancing effects before the drug is recommended as a viable fatigue countermeasure.

The effect of autogenic training and biofeedback on motion sickness tolerance.

BACKGROUND: Motion sickness is characterized by symptoms of vomiting, drowsiness, fatigue and idiosyncratic changes in autonomic nervous system (ANS) responses such as heart rate (HR) and skin temperature (ST). Previous studies found that symptoms of motion sickness are controllable through self-regulation of ANS responses and the best method to teach such control is autogenic-feedback (biofeedback) training. Recent experiments indicated that biofeedback training is ineffective in reducing symptoms of motion sickness or in increasing tolerance to motion. HYPOTHESIS: If biofeedback facilitates learning of ANS self-regulation then autogenic training with true feedback (TFB) should lead to better control over ANS responses and better motion tolerance than autogenic training with false feedback (FFB). If there is a relationship between ANS self-regulation and coping with motion stress, a significant correlation should be found between amounts of control over ANS responses and measures of motion tolerance and/or symptoms of motion sickness. METHOD: There were 3 groups of 6 subjects exposed for 6 weeks to weekly sessions of Coriolis stimulation to induce motion sickness. Between the first and second Coriolis sessions, subjects in the experimental groups received five episodes of autogenic training with either true (group TFB) or false (group FFB) feedback on their HR and ST. The control group (CTL) received no treatment. RESULTS: Subjects learned to control their HR and ST independent of whether they received true or false feedback. Learned control of ST and HR was not related to severity of motion sickness or subject's ability to withstand Coriolis stimulation following treatment. CONCLUSIONS: A lack of significant correlation between these variables suggested that subjects were not able to apply their skills of ANS self-regulation in the motion environment, and/ or such skills had little value in reducing symptoms of motion sickness or enhancing their ability to withstand rotations.

Modafinil, d-amphetamine and placebo during 64 hours of sustained mental work. I. Effects on mood, fatigue, cognitive performance and body temperature.

Modafinil is an alerting substance that is considered safer than amphetamine with fewer side effects. Although modafinil has been used successfully to treat narcolepsy, relatively little is known about its ability to ameliorate fatigue and declines in mental performance due to sleep deprivation (SD) in a normal population. Forty-one military subjects received either 300 mg of modafinil, 20 mg of d-amphetamine, or placebo on 3 separate occasions during 64 hours of continuous cognitive work and sleep loss. Three drug treatments were given: at 23.30 hours and 05.30 hours during the first and second SD nights, respectively, and once at 15.30 hours during the third day of continuous work. Subjective estimates of mood, fatigue and sleepiness, as well as objective measures of reaction time, logical reasoning and short-term memory clearly showed better performance with both modafinil and amphetamine relative to placebo. Both modafinil and amphetamine maintained or increased body temperature compared to the natural circadian cycle observed in the placebo group. Also, from subject debriefs at the end of the study, modafinil elicited fewer side-effects than amphetamine, although more than the placebo group. Modafinil appears to be a good alternative to amphetamine for counteracting the debilitating mood and cognitive effects of sleep loss during sustained operations.

Modafinil, d-amphetamine and placebo during 64 hours of sustained mental work. II. Effects on two nights of recovery sleep.

Polysomnograms were obtained from 37 volunteers, before (baseline) and after (two consecutive recovery nights) a 64-h sleep deprivation, with (d-amphetamine or modafinil) or without (placebo) alerting substances. The drugs were administered at 23.00 hours during the first sleep deprivation night (after 17.5 h of wakefulness), to determine whether decrements in cognitive performance would be prevented; at 05.30 hours during the second night of sleep deprivation (after 47.5 h of wakefulness), to see whether performance would be restored; and at 15.30 hours during the third day of continuous work, to study effects on recovery sleep. The second recovery night served to verify whether drug-induced sleep disturbances on the first recovery night would carry over to a second night of sleep. Recovery sleep for the placebo group was as expected: the debt in slow-wave sleep (SWS) and REM sleep was paid back during the first recovery night, the rebound in SWS occurring mainly during the first half of the night, and that of REM sleep being distributed evenly across REM sleep episodes. Recovery sleep for the amphetamine group was also consistent with previously published work: increased sleep latency and intrasleep wakefulness, decreased total sleep time and sleep efficiency, alterations in stage shifts, Stage 1, Stage 2 and SWS, and decreased REM sleep with a longer REM sleep latency. For this group, REM sleep rebound was observed only during the second recovery night. Results for the modafinil group exhibited decreased time in bed and sleep period time, suggesting a reduced requirement for recovery sleep than for the other two groups. This group showed fewer disturbances during the first recovery night than the amphetamine group. In particular, there was no REM sleep deficit, with longer REM sleep episodes and a shorter REM latency, and the REM sleep rebound was limited to the first REM sleep episode. The difference with the amphetamine group was also marked by less NREM sleep and Stage 2 and more SWS episodes. No REM sleep rebound occurred during the second recovery night, which barely differed from placebo. Hence, modafinil allowed for sleep to occur, displayed sleep patterns close to that of the placebo group, and decreased the need for a long recovery sleep usually taken to compensate for the lost sleep due to total sleep deprivation.

Electrophysiological recording and analysis during protracted continuous work experiments.

A system is described that allows electrophysiological data to be collected and analysed from sleep loss studies involving continuous cognitive work. This system needed to satisfy two major requirements. First, the electrophysiological hardware had to be able to record extended periods of physiology (often lasting 80 h) from multiple electrode sites and yet be portable enough to allow subject mobility. Second, a comprehensive yet flexible procedure had to be developed to temporally map the physiology to critical experimental events (e.g., all the behavioural tasks, sleeping and napping periods). The resulting system uses the Oxford Medilog 9000 for data acquisition and playback as well as a custom software environment to digitize and analyse these data.

Steady-state visual evoked responses in high and low alpha subjects.

Reactivity to photic stimulation was studied in 16 subjects who were divided into 2 groups based on the relative amounts of spontaneous EEG alpha produced during a 4 min eyes-closed baseline condition. During the experimental session the subjects were presented with thirteen 1 min periods of sinusoidally modulated light stimulation at frequencies ranging from 2 Hz below their spontaneous peak alpha frequency (SPAF) to 2 Hz above in 0.33 Hz intervals. Using FFTs, steady-state visual evoked responses (VERs) were extracted from each subject's EEG for each condition. VER magnitude for high alpha subjects varied with the proximity of the stimulus frequency to the SPAF, the VER for low alpha subjects did not. Conversely, low alpha subjects showed a similar effect in side-band alpha activity (once the VER had been extracted) whereas high alpha subjects did not. The results are explained in terms of a possible difference in the coupling strength between thalamic and cortical alpha sources.

Dream self-reflectiveness as a learned cognitive skill.

This research was directed toward the contradiction sustained by cognitive dream psychology, which on the one hand regards dreaming as higher symbolic activity and, on the other, sees its organizational and functional characteristics as derivative and/or inferior to those of waking consciousness. Study 1 evaluates the degree of self-reflective meta-cognition in dreams from different sleep stages. Subjects were 24 college students selected such that half were self-reported high-frequency dream recallers and half were low-frequency recallers. Both groups were composed equally of men and women. Greater self-reflectiveness (SR) was found in REM dreams as compared with those from stages 2 and 4, which did not differ. High-frequency recallers showed more dream SR than did low-frequency recallers. Study 2 assessed the extent to which self-reflective and lucid dreaming can be learned as a cognitive skill by varying levels of intention and attention paid to dreaming. After 3 weeks of home dream collection, results showed that four experimental groups had greater dream SR than did a baseline group. The most effective treatment was the mnemonic, wherein attention patterning schemas learned in waking resulted in more self-reflective and lucid dreaming than did either baseline or attention-control conditions. These results provide evidence that dreaming is not single-minded but variable along a self-reflective process continuum, and suggest functional and organizational levels that are consistent with the conception of dreaming as higher order cognitive activity.

Quantitative description of sleep stage electrophysiology using digital period analytic techniques.

The purpose of the current study was to assess the overlap in variance of two procedures for the quantification of sleep electrophysiology: conventional stage scoring and computer quantification of tonic activity. Data were collected on 24 nights from eight subjects and were scored according to a modified set of Rechtschaffen and Kales criteria and submitted to a period-analytic computer analysis. Following this, discriminant function analyses were performed on the data for each night to predict the visual stage scores from the computer-generated data. The results indicate a very high degree of predictive accuracy (91.05%) supporting the contention that the computer-quantified data set includes the variance normally captured by stage scoring. The implications of computer quantification of sleep electrophysiology are discussed.

A multivariate comparison between two EEG analysis techniques: period analysis and fast Fourier transform.

The present study investigated the statistical correspondence between two frequently used methods of analysing tonic EEG activity: (1) period analysis and (2) Fast Fourier Transforms (FFTs). For replication purposes, independent statistical analyses were carried out on the EEG of sleeping subjects and of awake subjects performing a cognitive task. From the results of two canonical correlations, the first two canonical variates were sufficient to account for 97% (awake group) and 99% (sleeping group) of the variance between the separate linear composites of all FFT and period analysis variables. Linear regressions of the 3 dependent measures generated by period analysis onto each respective FFT measure gave high and significant multiple correlations for all frequencies. Zero-order correlations were also gathered and discussed. It is concluded that period analytic and FFT analysed EEG share similar types of information and that period analysis can be used more often in EEG research.