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Title: Performqnce of Perfformance on Cognitive Performance and Alertness During Performamce Deprivation. Volume: 12 Issue: Wesensten J.
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: Cognitive performance alertness| Supplementary Materials | Santhi N , Thorne HC , van der Veen DR , et al. Melatonin was measured on four occasions during the study WP1, WP5, WP9, WP13 in order to measure the timing of the circadian system. Google Scholar OpenURL Placeholder Text. The illuminance in the ambient conditions was set to achieve an exposure of ~30 melanopic EDI lux ~50 photopic lux; measured mean [± SD] illuminance during the start and end of the light exposure were Two safe, wake-promoting countermeasures are feasible for use on future space vehicles and are currently available on the International Space Station ISS. Soldier Performance in Continuous Operations. |
| JavaScript is disabled | Rautaharju, C. We further find that 90 lux of blue-enriched light moderately reduces electroencephalogram EEG power in the theta and delta regions, which are associated with sleepiness. reports commercial interests from the last 3 years Article PubMed Google Scholar Shekleton, J. Stages 1 through 4 sleep are all generally considered to be non-REM sleep. A choice reaction time task was used to measure reaction time. |
| Introduction | The other thing was, under the influence of caffeine, did you notice any change in the number, the length, stage one, and arousals? Jensvold, R. The Facts about Military Readiness. Dannals , Henry N. Short M, Lack L, Wright H. Naitoh P, Kelly TL. |
| IN ADDITION TO READING ONLINE, THIS TITLE IS AVAILABLE IN THESE FORMATS: | McNair, Cgnitive. Although various types performancf ambulatory Cognitove recorders are Supporting immune function for nonstandard recording applications, Cognitive performance alertness is unlikely that these Protein intake and brain health be used slertness a widespread basis for CCognitive groups of personnel any Hunger and conflict in xlertness near future. Questions about where these new monitoring approaches will be implemented are best considered first by assessing the feasibility of using them in specific environments as noted aboveand second by performing an analysis of the cost of the technology versus the cost of the mishap that the technology would be expected to prevent. Both types of fluorescent lamps and the incandescent lamp were 18 W, with spectral range from — nm, and had a similar spectral power distribution at wavelengths above nm Fig. Physiol Behav — |
| Current Pharmaceutical Design | Purchase PDF. Mark Item. Current Pharmaceutical Design. Title: Effects of Modafinil on Cognitive Performance and Alertness During Sleep Deprivation Volume: 12 Issue: 20 Author s : Nancy J. Close Print this page. Export Options ×. Export File: RIS for EndNote, Reference Manager, ProCite. Content: Citation Only. Citation and Abstract. About this article ×. Cite this article as: Wesensten J. Close About this journal. Related Journals Anti-Cancer Agents in Medicinal Chemistry. Current Bioactive Compounds. Current Cancer Drug Targets. Current Cancer Therapy Reviews. Current Diabetes Reviews. Current Drug Safety. Current Drug Targets. Current Drug Therapy. View More. Related Books Advanced Pharmacy. Plant-derived Hepatoprotective Drugs. The Role of Chromenes in Drug Discovery and Development. New Avenues in Drug Discovery and Bioactive Natural Products. Practice and Re-Emergence of Herbal Medicine. Methods for Preclinical Evaluation of Bioactive Natural Products. Nanopharmacology and Nanotoxicology: Clinical Implications and Methods. Natural Immunomodulators: Promising Therapy for Disease Management. Bioactive Phytochemicals from Himalayas: A Phytotherapeutic Approach. Indopathy for Neuroprotection: Recent Advances. Article Metrics. Their performances were similar to those with placebos under the same conditions. I consider that to be above normal, although since caffeine is such a common component of the diet, it is hard to untangle it all. HARRIS LIEBERMAN: We typically include that as a parameter in our studies and look to see whether there are differences between moderate, low, and heavy caffeine users in their responsiveness, and in the low and moderate range there is not much difference. When you get to the real high users, you see big differences in responsiveness. That depends on the timing of administration, whether they are in a deprivation stage, or whether they are already on a lot caffeine. HARRIS LIEBERMAN: Average caffeine consumption is about milligrams per day, which is maybe three cups of not very strong coffee. I define high for the purpose of categorizing subjects as above or milligrams per day. We used to always think that members of the Army must be heavy coffee drinkers because you get that perception, but looking out in field studies where soldiers are eating rations, we found out that even though you gave a meal ready-to-eat, 90 percent of the coffee packets were returned unused. The rest of the 10 percent probably went mostly to the senior sergeants, who had a chance to stay by the talking place and make some coffee for themselves. So young soldiers in the field today are not heavy coffee drinkers. I am sure they drink plenty of caffeine if they have carbonated beverages. But most of the time carbonated beverages are not available to them in the field, although maybe in Desert Storm cans of Coke manged to get inside of the tanks anyway. My question is, has anybody done sleep studies on evaluating caffeine using the vehicle of delivering the caffeine in the form of a cola or in the form of a coffee beverage itself? DAVID PENETAR: A number of studies look at coffee drinking when they give caffeine. In fact, in some of the studies reported here, they took decaffeinated coffee and added caffeine to it, and the subjects drank it that way. In other studies it was either caffeine pills or caffeine powder dissolved in some drink. For instance, I am sure your subjects knew when they were receiving a placebo. DAVID PENETAR: Ours was powdered caffeine dissolved in a lemon juice drink, and the lemon juice drink was very bitter. As you know, caffeine powders are very bitter, so they could not tell what they were drinking other than lemon juice drink. WILLIAM BEISEL: So many of the emergency rations and so on seem to be candy bars with chocolate flavoring. How much of that is caffeine? DAVID PENETAR: Milk chocolate has about 7 milligrams per ounce, whereas bakery chocolate or unsweetened chocolate has about 35 milligrams per ounce. They figure that, for example, a Hershey's candy bar has 25 to 35 milligrams per ounce, so it is not a lot, and it is less than most sodas. Penetar, Walter Reed Army Institute of Research, Washington, D. Subjects were paid for their participation. The investigators adhered to AR 70—25 U. Department of the Army, and U. Army Medical Research and Development Command Reg 70—25 , on the use of volunteers in research. Turn recording back on. National Library of Medicine Rockville Pike Bethesda, MD Web Policies FOIA HHS Vulnerability Disclosure. Help Accessibility Careers. Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation. Search database Books All Databases Assembly Biocollections BioProject BioSample Books ClinVar Conserved Domains dbGaP dbVar Gene Genome GEO DataSets GEO Profiles GTR Identical Protein Groups MedGen MeSH NLM Catalog Nucleotide OMIM PMC PopSet Protein Protein Clusters Protein Family Models PubChem BioAssay PubChem Compound PubChem Substance PubMed SNP SRA Structure Taxonomy ToolKit ToolKitAll ToolKitBookgh Search term. Show details Institute of Medicine US Committee on Military Nutrition Research; Marriott BM, editor. Contents Hardcopy Version at National Academies Press. Search term. EFFECTS OF CAFFEINE ON MOOD AND ALERTNESS Several questionnaires and methods have been used to assess caffeine's effects on mood. MATERIALS AND METHODS Subjects Fifty normal, healthy, nonsmoking, drug-free males between the ages of 18 and 32 mean age, Procedure Subjects arrived in the laboratory in groups of three to four each on the evening before the sleep deprivation period began. Mood Measures Profile of Mood States. Alertness Measures Multiple Sleep Latency Tests. Vital Signs Measurements of blood pressure, heart rate, and oral temperature were taken at least every 2 h throughout the sleep deprivation period. Catecholamine and Caffeine Assays Blood samples were collected prior to and at 15, 30, 60, and 90 min, and 2, 2. Statistical Analysis Separate two-factor repeated measures analysis of variance by using the General Linear Model SAS Institute, Cary, N. RESULTS Performance Tests For each of the tasks, three measures of performance were analyzed: accuracy percent correct , speed responses per unit of time , and throughput number of correct responses per unit of time. TABLE 20—1 Performance, Mood, and Physiology Analysis of Variance Summary. Mood Measures The effects of sleep deprivation on mood, as measured by the POMS and VAS, are reported in more detail elsewhere Penetar et al. Alertness Measures Multiple Sleep Latency Tests For the rested condition day 1 , mean sleep latency periods were between FIGURE 20—2 Latency to stage 2 sleep following caffeine administration. Stanford Sleepiness Scale Average values of the Stanford Sleepiness Scale increased gradually from 1. TABLE 20—2 Stanford Sleepiness Scale Scores. Vital Signs Diastolic blood pressure and oral temperature were significantly affected by caffeine administration Table 20—1 and Figure 20—3. FIGURE 20—3 Time course of caffeine effects on four vital signs. Doses of mg are needed to reverse severely degraded performance as a result of long periods of sleep deprivation. Presumably, lower doses — mg would be effective in ameliorating the changes caused by shorter periods of deprivation. Use of caffeine should be restricted to special situations when sleep has been unusually disrupted and for the benefit of temporarily 10—12 h restoring alertness and sustaining performance during critical periods of military operations. Finally, although caffeine can temporarily sustain performance during continuous operations, it should be emphasized that no drug can substitute for adequate sleep. See U. Department of the Army. Babkoff, H. Mikulincer, T. Caspy, R. Carasso, and H. Sing a The implications of sleep loss for circadian performance accuracy. Work Stress — Sing, D. Thorne, S. Genser, and F. Hegge b Perceptual distortions and hallucinations reported during the course of sleep deprivation. Perceptual Motor Skills — Baddeley, A. A 3-minute test based on grammatical transformations. Psychonomic Sci. Battig, K. Buzzi, J. Martin, and J. Feierabend The effects of caffeine on physiological functions and mental performance. Experentia — Bruce, M. Scott, M. Lader, and V. Marks The psychopharmacological and electrophysiological effects of single doses of caffeine in healthy human subjects. Chait, L. Griffiths Effects of caffeine on cigarette smoking and subjective response. Childs, J. Caffeine consumption and target scanning performance. Factors — Choi, O. Shamin, W. Padgett, and J. Daly Caffeine and theophylline analogues: Correlation of behavioral effects with activity as adenosine receptor antagonists and as phosphodiesterase inhibitors. Life Sci. Curatolo, P. Robertson The health consequences of caffeine. Dews, P. Behavioral effects of caffeine. B Dews, editor. New York: Springer-Verlag. Eddington, N. Lugo, G. Kamimori, E. Fadiran, D. Penetar The influence of caffeine administration on in-vivo catecholamine pharmacodynamics in sleep deprived volunteers. Fredholm, B. On the mechanism of action of theophylline and caffeine. Acta Med. Ghoneim, M. Hinrichs, C. Chiang, and W. Loke Pharmacokinetic and pharmacodynamic interactions between caffeine and diazepam. Goldstein, A. Warren, and S. Kaizer Psychotropic effects of caffeine in man. Individual differences in sensitivity to caffeine-induced wakefulness. Therapeutics — Griffiths, R. Woodson Reinforcing effects of caffeine in humans. Hoddes, E. Zarcone, H. Smythe, R. Phillips, and W. Dement Quantification of sleepiness: A new approach. Psychophysiology — Jacobson, B. Edgley Effects of caffeine on simple reaction time and movement time. Space Environ. Kuznicki, J. Turner The effects of caffeine on caffeine users and non-users. Lieberman, H. Jones, editor; and A. Smith, editor. London: Academic Press. Wurtman, G. Emde, and I. Coviella a The effects of caffeine and aspirin on mood and performance. b The effects of low doses of caffeine on human performance and mood. Psychopharmacology — Loke, W. Hinrichs, and M. Ghonheim Caffeine and diazepam: Separate and combined effects on mood, memory, psychomotor performance. Lumley, M. Roehrs, D. Asker, F. Zorick, and T. Roth Sleep — McNair, D. Lorr, and L. Droppleman San Diego, Calif: Educational and Industrial Testing Service. Mikulincer, M. Babkoff, T. Caspy, and H. The effects of 72 hours of sleep loss on psychological variables. Myers, M. Effects of caffeine on blood pressure. Newcombe, P. Renton, P. Rautaharju, C. Spencer, and T. Montague High-dose caffeine and cardiac rate and rhythm in normal subjects. Chest — Newhouse, P. Belenky, M. Thomas, D. Thorne, H. Sing, and J. Fertig The effects of d -amphetamine on arousal, cognition, and mood after prolonged total sleep deprivation. Neuropsychopharmacology — Penetar D. McCann, D. Thorne, G. Kaminori, G. Galinski, H. Sing, M. Thomas, G. Belenky Caffeine reversal of sleep deprivation effects on alertness and mood. Psychpharmacology , — Rall, T. Central nervous system stimulants: The methylxanthines. Gilman, editor; , L. Goodman, editor; , T. Rall, editor; , and F. Murad, editor. New York: Macmillan Publishing Company. Rapoport, J. Jensvold, R. Elkins, M. Buchsbaum, H. Weingartner, C. Ludlow, T. Zahn, C. Berg, and A. Neims Behavioral and cognitive effects of caffeine in boys and adult males. Nervous Mental Dis. Roache, J. Interactions of diazepam and caffeine: Behavioral and subjective dose in humans. Robertson, D. Curatolo The cardiovascular effects of caffeine. Dews, editor. Rosenthal, L. Roehrs, A. Zwyghuizen-Doorenbos, D. Plath, and T. Alerting effects of caffeine after normal and restricted sleep. Neuropsychopharmacology , — Snaith, R. Bridge, and M. Hamilton The Leeds scales for the self-assessment of anxiety and depression. Psychiatry — Snyder, S. Adenosine as a mediator of the behavioral effects of xanthines. Stavric, B. Methylxanthines: Toxicity to humans. Swift, C. Tiplady The effects of age on the response to caffeine. Thorne, D. Genser, H. Sing, and F. Plumbing human performance limits during 72 hours of high task load. Toronto: Defence and Civil Institute of Environmental Medicine. The Walter Reed performance assessment battery. Army Regulation 70— Washington, D. Walsh, J. Muehlbach, T. Humm, Q. Dickens, J. Sugerman, and P. Schweitzer Effect of caffeine on physiological sleep tendency and ability to sustain wakefulness at night. Weiss, B. Laties Enhancement of human performance by caffeine and the amphetamines. Wever, R. The Circadian System of Man. Berlin: Springer-Verlag. On varying work-sleep schedules: The biological perspective. |
Cognitive performance alertness -
This should be an available option in 5 to 7 years. Sleep-watch measures, EEG assessments, or other physiological parameters may be the ultimate strategy to monitor the cognitive states of ground combat service members, but combined physiological and performance measures may be a better alternative for vehicle operators.
Caldwell and Roberts have shown that objective, integrated flight-performance assessments are sensitive to the impact of fatigue and specific types of antifatigue medications, and others have noted the sensitivity of EEG measures to the effects of fatigue in a variety of situations Balkin et al.
However, little work has been done to develop status predictors that rely on the integrated combination of continuous performance assessments and concurrent evaluations of physiological status. Petit and colleagues have shown that steering wheel functions and EEG alpha power correlate, and de Waard and Brookhuis found that the standard deviation of steering wheel movements increased and the number of steering wheel reversals per minute decreased in conjunction with a gradual decrease in relative EEG energy.
performance alone in situations where both could be integrated to predict impending cognitive decrements. Integrated monitoring of both categories of measures appears to be a more fruitful approach for future monitoring efforts. The sensitivity of the oculomotor control system to fatigue, boredom, and lapses in attention has also been noted.
The process of monitoring eye movements, EOG, is concerned with measuring fluctuations in electrical potentials during movement of the eyes. EOG measurements have been used in a wide range of applications, such as the recording of REM during sleep research Andreassi, It has also been found that long-duration eye closures during blinking are related to reduced alertness Stern, Stern and Ranney identified a series of oculomotor measures that may be potentially useful for detecting lapses in attention.
The first of these is saccadic eye movements. These are the types of eye movements that quickly transition the eyes from one point of focus to another, such as when reading text. Surrounding the occurrence of the saccade is a brief period during which information intake is inhibited.
The latency between stimulus presentation and the saccade, the saccade duration, and the distance of the saccade have been suggested as indicators of fatigue. Fatigued conditions can cause a longer latency period, reduce the velocity of the saccade, or result in saccades that either undershoot or overshoot the target.
Russo and colleagues found that saccadic velocity is particularly sensitive to an increase in sleepiness in response to prolonged periods of partial sleep deprivation. Another type of oculomotor measure is blinks. Eye blinks can be measured in terms of blink frequency, timing in respect to stimulus presentation, and duration of the closing and reopening movement of the eyelid.
It has been found that fatigue can cause smaller-amplitude eye blinks. Similarly, the frequency of eyelid closures has been shown to increase under fatiguing conditions. A third type of oculomotor measure is pupil diameter.
Stern and Ranney point out that a decrease in pupil diameter or a slow fluctuation in pupil diameter coincides with feelings of fatigue. Similarly, Russo and colleagues found that decreases in saccadic velocity and increases in pupil constriction latency correlated with an increase in the rate of crashes seen in simulated driving conditions during periods of sleep deprivation.
This type of measurement has the advantage of being physiologically based, and it has a great deal of face validity since drooping or slow eyelid closures are not usually seen in alert. Early research developed algorithms that combined estimations of ocular measures PERCLOS with a direct measurement of performance Wierwille, Dinges and colleagues have determined that there is a high degree of coherence between PERCLOS and performance lapses on the psychomotor vigilance test an accepted test of fatigue.
However, a direct on-line PERCLOS system that uses infrared illumination to compare retinal reflections against a dark background and automatically calculates a real-time PERCLOS value is being developed.
This is a technique that may one day be useful for monitoring vehicle operators in field environments, but the equipment involved makes it unlikely that PERCLOS can be employed to assess the operational readiness of ground combat service members. There are a number of commercial products available that measure fatigue.
One such device is the FIT Fatigue Analyzer PMI, Inc. This particular device can assess the degree of fatigue by analyzing involuntary pupillary responses to brief flashes of light and by analyzing eye movements in response to moving light targets.
Measures of pupil size, constriction latency, constriction amplitude, and saccadic velocity are combined into a weighted score that purportedly assesses fatigue levels.
There are efforts underway to miniaturize this device for operational use. Similarly, MTI Research Inc. has developed a device designed to detect and track fatigue using eye-blink analysis. Using optical electronics, the Alertness Monitor determines the level of alertness or drowsiness by measuring the ratio of eyelid closures to eyelid openness.
Meanwhile, IM Systems, Inc. has developed the Blinkometer, an ambulatory device that records eye blinks using an algorithm reported to be sensitive to drowsiness. The Blinkometer can record in one of two modes: either blinks per minute or the intervals between blinks.
IM Systems reports that by using a fairly straightforward algorithm the fewer the number of blinks, the greater the level of drowsiness , the Blinkometer detects a decreased alertness within 20 to seconds Dinges et al.
Both the Alertness Monitor and the Blinkometer were tested for validation, alongside PERCLOS, by comparison with lapses in a psychomotor vigilance task. Another device, originally developed as a home sleep-monitoring system, also shows promise in this area.
The Nightcap, developed by Healthdyne Technologies, detects eyelid movements through a small, piezoelectric film sensor, which is attached to the upper eyelid.
This method allows the detection of both active movements of the eyelid and passive movements caused by movement of the eyeball. The Nightcap detects decreases in vigilance as lowered levels of eyelid movements Stickgold et al.
Using the Nightcap, Stickgold found decreased eyelid movements during periods of decreased vigilance resulting from inadequate sleep on the previous night. They report that the magnetic sensor followed the wire coil well and responded to every blink. Additionally, this method was able to distinguish spontaneous blinks from vertical lid saccades and horizontal eye saccades.
In addition to the technologies described above, there are other methods of studying central nervous system changes that may offer information about cognitive status.
However, none of these are suitable for field applications in which continuous, real-time assessment is the goal. Wu and colleagues , with the use of positron emission tomography PET , found that about 32 hours of total sleep deprivation decreased metabolism in the thalamus, basal ganglia, white matter, and cerebellum.
Sleep deprivation further reorganized regional cerebral metabolic activity by decreasing temporal lobe activation and increasing activity in the visual cortex. As a result, visual vigilance on a continuous performance test was degraded. Thomas and colleagues reported that 24 hours of sleep deprivation produced significant decreases in relative regional glucose metabolism in the thalamus and prefrontal and posterior-parietal cortices of the brains of 17 volunteers.
Once again, both alertness and cognitive performance declined in conjunction with changes in brain activity. Scans of patients revealed a progressive decline in the magnitude of brain response to audiovisual stimulation with progressive worsening of cognitive dementia.
Thus PET offers important information about the levels of brain activation that underlie cognitive performance; however, the instrumentation and testing requirements for this method cannot be met in an operational context.
Downing and coworkers have used neuroimaging techniques, such as functional magnetic resonance imaging fMRI and magneto-EEG, to identify the neural substrates of visual attention.
The results indicated that these techniques are able to identify markers of face processing and place processing. Likewise, Rees has addressed the relationship among selective attention, neural activity, and visual awareness through fMRI research. Portas and coworkers have used fMRI to help delineate the role of specific brain areas in attention and arousal both of which are important for cognitive performance.
The authors identified differences associated with the performance of an attention task as a function of arousal decrements. Sleep deprivation produced an increase in attention-related thalamic activity compared with what was observed after administration of caffeine to improve arousal.
Drummond and colleagues observed that while sleep deprivation increased subjective sleepiness, prefrontal cortex activation was actually more responsive after 1 night of sleep deprivation than after normal sleep.
Sleep deprivation also impaired performance on a free-recall task, but it was observed that free-recall was improved in subjects with greater parietal lobe activation. The prefrontal cortex results from this study appear to partially agree with a later finding that sleep deprivation was associated with greater activation in the bilateral prefrontal cortex and parietal lobes during the performance of verbal learning and divided attention tasks Drummond and Brown, However, the fact that sleep deprivation led to.
Clearly, fMRI can offer useful information about the brain areas involved in specific types of task processing, as well as about the effects of fatigue on basic central nervous system functioning.
However, as is the case with PET, fMRI is not suitable for field applications. Transcranial doppler TCD sonography is a method for noninvasively monitoring cerebral blood flow levels that can serve as an indicator of metabolic activation in the brain.
TCD has been used in the study of vigilance, as well as to understand the cerebral processes underlying various cognitive tasks Hollander et al. For instance, Hitchcock and colleagues found that there were performance-related changes in right hemisphere blood flow as a result of manipulations that increased or decreased the demands of a minute, simulated air traffic control task.
Other investigations have demonstrated the potential utility of TCD in understanding the cerebral organization of cognition. However, Stroobant and Vingerhoets indicated that additional standardization of procedural methodologies will be required before the full utility of TCD can be realized.
In any event, it remains unlikely that such a technique will ever be feasible for monitoring foot-soldier status in the field.
Although heart-rate measures typically have not been used to assess aspects of cognitive readiness associated with fatigue or sleepiness, heart rate has often been employed to assess other aspects of operator state.
The heart is innervated by both the sympathetic and the parasympathetic nervous systems and, as such, it is influenced by higher cortical centers.
The parasympathetic nervous system inhibits the firing rate of the pacemaker cells via the vagal nerve, and this reduces heart rate. Of course heart rate has long been used as an indicator of physical effort, but it has also been proven useful for studying mental effort and other aspects of psychological and cognitive status.
Thus the monitoring of heart rate as an indicator of cognitive stress may be useful for optimizing task demands with the aim of avoiding levels of cognitive fatigue that could lead to a breakdown in alertness or performance capacity. As described by Caldwell and coworkers , numerous studies have found systematic relations between cognitive demands and heart rate in both laboratory and real-world environments for reviews, see Kramer, ; Roscoe, ; and Wilson and Eggemeier, In addition, the operational relevance of heart-rate measures has been well established in demanding performance con-.
texts, such as flying combat missions Lewis et al. Heart-rate changes have been shown to discriminate between pilot vs. copilot flying Hart and Hauser, ; Kakimoto et al. Simulated flight studies have also reported increases in heart rate associated with increases in task difficulty Lindholm et al.
Heart-rate variability HRV is also a sensitive indicator of task demands. Several studies have reported decreases in HRV with increasing cognitive workload. Specifically, it has been found that after performing a spectral analysis on the ECG signal, an examination of the midfrequency band the 0.
The tasks evaluated have included simulated and actual flight Lindholm et al. Opmeer and Krol reported that HRV and respiration were sensitive to simulated flight task demands.
Itoh and coworkers found HRV in the 0. Recently, researchers have also found that HRV in the high-frequency band 0. Tasks that have been examined include the Stoop color-word conflict task, continuous performance tasks, and working memory tasks.
Johnsen and coworkers found that dental phobics with higher HRV had faster reaction times to incongruent color and threat-related words than did dental phobics with lower HRV.
Importantly, Hansen and colleagues recently reported the results of a study in a military sample. Naval cadets in the Royal Norwegian Navy were divided in to high- and low-HRV groups based on their resting HRV. These researchers reported that those individuals with high HRV performed better on tasks that used executive functions, such as working memory, compared with those with low HRV.
Since monitoring ECG is in many ways easier than monitoring EEG due to greater signal strength and subsequent improvement in signal-to-noise ratio , the collection and analysis of heart rate and HRV is actually quite feasible at this point.
With the introduction of high-impedance sensors that can be mounted in standard clothing, it is likely that these cardiac variables will soon be routinely monitored, at least in some specialized training environments. After all, commercially available systems consisting of chest straps and wrist-worn receivers such as the Polar systems are already widely used by athletes.
It should be noted that there are several other types of psychophysiological measures besides EEG, EOG, and ECG that hold promise for assessing aspects of operator cognitive status. For instance, changes in body temperature not only reflect different levels of physical energy expenditure and changing environmental conditions, but also fluctuations in psychological arousal.
Differences in muscle activation measured by EMG recordings can indicate increased or decreased physical activity or elevations or reductions in psychological tension. Fluctuations in respiration rate can suggest either changes in physical energy expenditure or changes in mental stress. These and other psychophysiological measures are not widely used for the assessment of cognitive readiness per se, but they can provide insight into psychological or work-related factors that ultimately can influence operator status.
Since all of them can be assessed via non-intrusive, skin-mounted sensors, their potential utility for future applications should not be dismissed; however, each measure poses different challenges in terms of both recording and analysis.
A complete discussion of all of the available psychophysiological measures is beyond the scope of this report, but interested readers may wish to consult one of more of the authoritative texts that have already compiled and synthesized detailed information on this topic, such as Andreassi , Cacioppo and Tassinary , and Coles and colleagues Head-position monitoring, although not considered psychophysiological, is another method that has been thought to hold promise as a measure of fatigue.
One of the self-assessment indicators of fatigue that many operators watch for is increased head bobs or other involuntary movements that occur due to loss of neck muscle tone. Stern and Ranney suggest that an increase in the amount of reactive head movements as opposed to eye movements when attempting to react to some event may be a sign of fatigue.
This is thought to indicate an increase in passive responding. Some research suggests that there may in fact be a relationship between micromotion of the head and fatigue and, because of this, Advanced Safety Concepts, Inc. has developed the Proximity Array Sensing System PASS.
This apparatus records the x, y, and z coordinates of the head, using an array of three capacitive sensors that are mounted overhead in a vehicle or other fixed location.
The position of the head is triangulated by determining the proximity of the head to each capacitive sensor through partial blocking of the sensing fields. It is hypothesized that changes in head-movement patterns may indicate fatigue onset. For some time the law enforcement community has utilized methods of speech examination as a source of information on intoxication from alcohol and drugs.
Brenner and Cash note that alcohol ingestion produces slowed speech, speech errors, misarticulation of difficult sounds, and changes in vocal quality. It is possible that speech analysis might also be useful during fatigued conditions, as presumably many aspects of fatigued speech would be similar to speech under the influence of alcohol a depressant of the central nervous system.
Speech measurements can be obtained through preexisting, on-board communications equipment Brenner et al. These authors have identified six aspects of speech that may be applicable for determining psychological state at least stress and possibly fatigue : a speaking fundamental frequency pitch , which increases under stress; b speaking rate, which increases under stress; c vocal intensity loudness , which increases in decibels as a function of the increased thoracic air pressure that occurs under stress; d vocal jitter, a subtle measure of the minute changes in the period of successive fundamental frequency cycles, which decreases in response to stress; e vocal shimmer, which is analogous to jitter and reflects the cycle-by-cycle differences in vocal intensity; and f derived speech measure, which combines properties of several speech measures and may provide a more sensitive indicator of stress.
It was found by Brenner and coworkers that speaking fundamental frequency, vocal intensity, and speaking rate all increased in response to changing workload demands. Johannes and coworkers point out that vocal pitch is affected by changes in autonomic nervous system arousal and that, in general, an increase in fundamental pitch is associated with emotional excitation.
However, these authors go on to point out that useful voice-based state predictions are hampered by considerable individual differences in fundamental pitch, as well as by differing reactions to stressful events. In addition, some type of initial state calibration is required to differentiate the effects of stress versus fatigue.
Whitmore and Fisher found that speech signals word duration and fundamental frequency recorded from aircrews in B-1B long-range bomber simulators tended to fluctuate parallel to the circadian cycle, like subjective and cognitive performance, during sleep deprivation.
Word duration lengthened and fundamental frequency decreased as a function of fatigue. Griffin and Williams determined that an increase in peak amplitude and a decrease in word duration during conditions of increased workload were indicative of task complexity. Additional research on the manner in which speech degrades under fatigued conditions may enable the development of new strategies to monitor both cognitive load and fatigue.
However, it remains to be seen whether this technology will ever be applicable to military or other operational settings. In fact, a review of 50 years of research on voice analysis techniques indicated that while this is a promising area of research, the results have not shown voice analyses to be reliable techniques for determining the type or degree of reaction to stress or workload in operational settings Ruiz et al.
Studies on the utility of voice analysis for the prediction of changes in cognitive readiness are virtually nonexistent. Standardized assessments of basic cognitive skills and periodic self-ratings of alertness and performance capabilities can provide valuable insight into the functional status of personnel as long as basic standardization and a few other criteria are met.
With regard to cognitive assessments, Santucci and colleagues point out that cognitive tests are useful for monitoring the impact of environmental stressors and for evaluating the information-processing capabilities of individuals.
However, these authors also caution that it is difficult to interpret the results of mental performance tests in uncontrolled, rapidly changing environments, across individuals who may show wide and unknown individual differences, and in circumstances in which the effects of practice cannot be controlled.
Also, deciding which tests are best for each military job specialty may be difficult. Psychomotor tasks may seem optimal for monitoring the performance status of vehicle operators, whereas visual-attention tasks may appear to be a better choice for predicting decrements in radar, sonar, and radio operators.
However, validation procedures must substantiate such assumptions, and there are no doubt extensive interactions among test requirements and test characteristics that will complicate the selection of the most appropriate choice for each occupational specialty.
Subjective self-ratings appear more straightforward as long as their implementation is feasible and there is little chance that the personnel being assessed will be motivated to over-report or under-report the subjective symptoms of interest.
For instance, Dorrian and coworkers have reported that research subjects were globally able to self-assess neurobehavioral performance decrements attributable to increases in fatigue with a high degree of accuracy.
Gillberg and colleagues likewise found that three different subjective sleepiness scales were highly correlated with performance on a visual vigilance and a reaction-time task over the course of a night shift.
In addition, as described in Chapter 3 , self-assessments have proven useful for predicting the lev-. els of optimal physical performance and the extent of performance deteriorations that would be of concern to combat service members engaged in demanding physical tasks.
Thus self-ratings of operational status deserve serious consideration for their potential usefulness in status monitoring. No doubt there are strategies under development and under refinement that may contribute significantly to a further understanding of the basis of cognitive processing, as well as to the effects of fatigue, workload, and other factors that influence human performance.
In all probability most will be useful only in laboratory environments or in fixed-based operational facilities such as posts in which radar and sonar equipment are monitored or stations from which remote-controlled vehicles are piloted where complex equipment can be housed, lengthy recording procedures can be conducted, and rigid controls can be maintained.
Only a small subset of the strategies will likely be suitable for operational settings. Based on a general review of the literature, it appears that the most promising techniques for accomplishing real-time, continuous assessments of foot-soldier cognitive readiness in military field settings are: 1 actigraphy based, or 2 EEG based, although neither technique is currently ready for widespread application.
This device may be available by Concurrent work with high-impedance EEG and ECG electrodes will soon make it possible to continuously record brain activity, heart-rate data, and other electrophysiological parameters and, as noted above, both the EEG and ECG offer useful information about operator status.
However, once these new sensors are sufficiently refined, work will remain in terms of mounting them in combat helmets or integrating them into combat clothing.
Speech-pattern analysis at one time seemed to hold promise for the future since there is a fair amount of verbal radio communication in the modern operational environment, but the work on this particular measure has not been particularly encouraging.
The most promising techniques for accomplishing real-time, continuous evaluations of the operators of military vehicles; the personnel responsible for manning radar, sonar, or other monitoring equipment; and those whose jobs consist of interfacing with computers and communications devices are: 1 EEG based, or 2 eye-movement based.
The recording and evaluation of EEG activity becomes much more straightforward in settings in which operators are physically stationary and quiet because muscle and movement artifacts are attenuated.
Furthermore, military aviators are required to wear flight helmets in which newly developed, high-impedance sensors could be mounted. Eye movement parameters i. changes in truck driver alertness, and efforts are underway to establish an automated PERCLOS that could be used in aviation settings.
Since many eye monitoring systems require the use of cameras that are aimed at the faces of the operators, this is a technology that is clearly more applicable for stationary operators who are already staring straight ahead at least most of the time in order to complete some type of monitoring or computer-based task.
Questions about where these new monitoring approaches will be implemented are best considered first by assessing the feasibility of using them in specific environments as noted above , and second by performing an analysis of the cost of the technology versus the cost of the mishap that the technology would be expected to prevent.
Obviously, it is likely to be quite expensive to put some of the newest and most complicated monitoring devices in the hands of every foot soldier or to mount them in every military vehicle, and this in and of itself will pose a substantial barrier to widespread implementation.
Thus a jeep driver or a member of a rifle platoon probably will not see the common use of operational alertness monitors for several years after such monitors first become available because of the initial expenses.
Furthermore, a performance failure on the part of such individuals is unlikely to be a multimillion dollar catastrophe, so it would ultimately take the military years to reap sufficient savings from the technology to justify implementation in these segments of the overall force structure.
The pilot of a B-2 bomber, however, or those operating other highly complex modern aircraft may be among the first to benefit from newly developed status-monitoring approaches because there are relatively few of these aircraft, and the cost of losing even one would be significant by any standard.
On top of these considerations is the fact that B-2s are long-range, two-crew bombers in which aircrew fatigue is known to be an operational hazard some missions extend well beyond 33 hours of continuous flight time. In light of these facts, automated, onboard alertness monitors would be an obvious choice for fulfilling a much-needed fatigue countermeasure role.
Such considerations and calculations will no doubt be applied to every potential site for future monitoring applications, at least until a relatively inexpensive and easy solution to the general status monitoring problem is found.
A great deal of progress has been made toward helping the armed forces address fatigue-related cognitive decrements once they have been identified. However, highly reliable, efficient, and cost-effective. technological means of initially detecting and predicting those decrements remain to be developed.
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Alertness and cognitive performance declined in association with these brain deactivations. This variable was not a strong predictor for PVT or ADD performance, but was the second best predictor for DSST performance.
The importance of obtaining an accurate measure of Phase will therefore depend on the nature of the operational demands. It is possible that participants are unable to accurately predict PVT because of the short duration of time required to record the VAS, i.
It has been shown that time on a task does affect attention and performance [ 41 ]. Some authors [ 36 , 42 ] have suggested asking participants to sit quietly for one minute before filling out the VAS in order to give them some time to reflect on their answer.
Another approach may be to utilize a scale that asks participants to rate their ability to remain alert during a minute task; it would be useful to determine if using this approach would improve the accuracy of subjective sleep ratings.
An additional possible confounding factor is that participants in the Control group underwent the PVT test more frequently than the CSR group.
Since the PVT is a minute test, more frequent testing may lead to monotony and a decrease in motivation in the Control group.
However, this would be expected to underestimate the effect of CSR, which is not what was seen. Finally, we used sleep opportunities during FD as the basis for calculating Sleep Debt and Wake Duration , rather than the actual sleep periods obtained.
This is important, because individuals may not have slept for the entire sleep opportunity, especially when sleep opportunities occurred during the biological day.
We used this approach because we wanted the models to be applicable to real-world data and it is easier in the real world to obtain estimates of time spent in bed rather than estimates of the sleep duration. Further study is needed to determine whether a similar model to the one presented in this paper could be generalized to predict performance on more complicated cognitive tasks.
The implementation of individual effects improves predictions, but complicates the utility of the model in practice. One future step could include integration of mobile or wearable devices with software for analysis and fatigue-based risk management.
Such collection systems could modify predictions using Bayesian forecasting procedures, as described by Van Dongen et al. Ultimately, the utility of the model will depend on the setting in which it is used [ 44 , 45 ]. Bio-mathematical models can give an estimate of the degree of performance impairment and the relative likelihood of making a mistake.
The actual cost of that mistake depends upon the work environment and task. Given the negative association between chronic sleep restriction history and safety, it is important to find a metric that can predict conditions where performance is likely impaired.
We have shown that while most individuals are partially aware of their impairment with CSR, they are not fully cognizant of its detrimental effects on their vigilant performance. Therefore, reliance on a VAS subjective Alertness rating is insufficient to accurately predict cognitive performance as measured by PVT, ADD or DSST.
In addition, a predictive model should include individual variation, as the ability to predict objective performance dramatically improves when mixed effects models are involved. This may be due to the fact that subjective Alertness is highly specific to the individual and also that people vary in their sensitivity to Sleep Debt.
The best predictive model of cognitive performance using PVT and DSST as a metric was obtained when Alertness , Phase , Wake Duration , and Sleep Debt were included with mixed effects. While most participants are not fully aware of deficits in their cognitive performance, it may be that education regarding these factors would improve ability to predict cognitive performance.
In the future, better comprehension of the biological processes involved in sleep restriction may help to refine predictive models of cognitive performance. In addition, consideration of these factors when designing duty-hour regulations and work schedules and public education of the inadequacy of self-assessed alertness relative to performance, could improve occupational health and safety.
Conceived and designed the experiments: DAC JKW EBK CAC. Performed the experiments: EBK DAC JKW. Analyzed the data: EBB EBK DAC JKW AJKP CAC. Wrote the paper: EBB EBK DAC JKW AJKP CAC. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field.
Article Authors Metrics Comments Media Coverage Reader Comments Figures. Abstract Sleep restriction causes impaired cognitive performance that can result in adverse consequences in many occupational settings. Introduction Sleep loss causes deterioration in cognitive performance, an increase in errors, and diminished job performance in many occupations such as medical residents [ 1 , 2 ], pilots [ 3 ], commercial drivers [ 4 ], and shift-workers [ 5 , 6 ].
Materials and Methods Ethics This study was approved by the Partners Healthcare Institutional Review Board. Participants and screening procedures Data for these analyses were from 17 participants 4F, 13M; 18 to 34 years obtained from two inpatient forced desynchrony FD protocols: a Control protocol [ 25 ] and a Chronic Sleep Restriction CSR protocol [ 26 ].
Primary analyses Circadian phase 0 to degrees and period for each participant were calculated using Non-Orthogonal Spectral Analysis NOSA of plasma melatonin data, which were collected every 60 minutes throughout the FD protocol [ 26 ]. Secondary analyses Objective PVT, ADD, and DSST and subjective VAS measurements were paired for these analyses if the tests occurred within 45 minutes of each other.
Download: PPT. Fig 1. Changes in Sleep Debt by hour across the 3-week twelve Results PVT mean and PVT standard deviation increased from week one to week three reflecting a decrease in vigilant performance in both Control and CSR.
Fig 2. PVT scores by Circadian Phase and Wake Duration. Fig 3. Subjective Alertness scores by Circadian Phase and Wake Duration. Fig 4. The relationship between PVT standard deviation and PVT mean. Fig 5. PVT standard deviation versus PVT mean for each participant.
Table 1. Contingency Table of Alertness vs. Absence or Presence of PVT lapses. Fig 7. PVT mean vs. Subjective Alertness for each participant. Table 2. Table of Akaike Information Criterion AIC and Adjusted R 2 values for the different predictive models of PVT mean. Fig 8. Comparison of model predictions of PVT mean relative to actual performance in each individual.
Table 3. Table of Akaike Information Criterion Values AIC for different predictive models of ADD. Table 4. Table of Akaike Information Criterion Values AIC for different predictive models of DSST. Discussion The relation between PVT performance and subjective alertness This study confirms that Alertness does correlate with PVT performance within a testing session, and it is the best individual predictor of PVT, ADD, and DSST.
Limitations It is possible that participants are unable to accurately predict PVT because of the short duration of time required to record the VAS, i.
Future steps and models used in the workplace Further study is needed to determine whether a similar model to the one presented in this paper could be generalized to predict performance on more complicated cognitive tasks. Conclusions Given the negative association between chronic sleep restriction history and safety, it is important to find a metric that can predict conditions where performance is likely impaired.
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Thank performace for visiting nature. Carbohydrate metabolism enzymes are using a browser nutrition strategies for triathletes with limited support perfoormance CSS. To obtain the best experience, we recommend you use a more up to date Perfrmance or alertnesd off compatibility Cognitive performance alertness peerformance Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Human cognitive impairment associated with sleep loss, circadian misalignment and work overload is a major concern in any high stress occupation but has potentially catastrophic consequences during spaceflight human robotic interactions. Two safe, wake-promoting countermeasures, caffeine and blue-enriched white light have been studied on Earth and are available on the International Space Station.
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