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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mental fatigue, with decreased concentration capacity, is common in neuroinflammatory and neurodegenerative diseases, often appearing prior to other major mental or physical neurological symptoms. Mental fatigue also makes rehabilitation more difficult after a stroke, brain trauma, meningitis or encephalitis. As increased levels of proinflammatory cytokines are reported in these disorders, we wanted to explore whether or not proinflammatory cytokines could induce mental fatigue, and if so, by what mechanisms.It is well known that proinflammatory cytokines are increased in major depression, "sickness behavior" and sleep deprivation, which are all disorders associated with mental fatigue. Furthermore, an influence by specific proinflammatory cytokines, such as interleukin (IL)-1, on learning and memory capacities has been observed in several experimental systems. As glutamate signaling is crucial for information intake and processing within the brain, and due to the pivotal role for glutamate in brain metabolism, dynamic alterations in glutamate transmission could be of pathophysiological importance in mental fatigue. Based on this literature and observations from our own laboratory and others on the role of astroglial cells in the fine-tuning of glutamate neurotransmission we present the hypothesis that the proinflammatory cytokines tumor necrosis factor-alpha, IL-1beta and IL-6 could be involved in the pathophysiology of mental fatigue through their ability to attenuate the astroglial clearance of extracellular glutamate, their disintegration of the blood brain barrier, and effects on astroglial metabolism and metabolic supply for the neurons, thereby attenuating glutamate transmission. To test whether our hypothesis is valid or not, brain imaging techniques should be applied with the ability to register, over time and with increasing cognitive loading, the extracellular concentrations of glutamate and potassium (K+) in humans suffering from mental fatigue. At present, this is not possible for technical reasons. Therefore, more knowledge of neuronal-glial signaling in in vitro systems and animal experiments is important.In summary, we provide a hypothetic explanation for a general neurobiological mechanism, at the cellular level, behind one of our most common symptoms during neuroinflammation and other long-term disorders of brain function. Understanding pathophysiological mechanisms of mental fatigue could result in better treatment.
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PMID:On the potential role of glutamate transport in mental fatigue. 1552 5

Technological trends and advances in automation have underscored the importance of task performance of certain jobs requiring mental functions such as information processing and decision analyses. Most experts agree that such work environments produce increased mental activities, with profound implications for mental fatigue and stress. Consequently, productivity measurement and improvement for white collar or 'knowledge worker' occupations remains a major challenge and concern. This investigation defines an experimental approach that examines the neurophysiological correlates of white collar worker mental fatigue using the EEG signal. A 6 h laboratory experiment was conducted to simulate work output. The methods of assessing fatigue employed were mental tests and physiological measurements. The experiment involved reading of standardized texts, finding solutions to arithmetic-logical problems and a combination of both task types. Two primary performance measures were obtained, work output and brain waves. Fast Fourier transform and correlation analyses are used to quantify the relationship between certain brain waves and mental fatigue. This research is a major step towards the development of a model that explores the relationship between mental fatigue and factors associated with output performance, optimal recuperation periods and related variables. Such a model would be useful in human reliability prediction based on task parameters and worker profiles.
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PMID:On the investigation of the neurophysiological correlates of knowledge worker mental fatigue using the EEG signal. 1567 87

The effects of a 20-min nap during 2 h of visual display terminal (VDT) work were examined. Ten young healthy adults took a 20-min nap or a 20-min rest I h after VDT work, followed by another 1 h of VDT work. A 20-min rest temporarily restored subjective sleepiness, but it deteriorated during the additional 1 h of work. In contrast, a 20-min nap maintained subjective alertness and performance level at a higher level and mental fatigue at a lower level for the additional 1 h of work. These results suggest that a short nap would be useful to both fatigue recovery and fatigue prevention during continuous VDT work. The present findings may provide a new work/rest strategy.
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PMID:Short nap versus short rest: recuperative effects during VDT work. 1569 69

Exposure to Magnetic Fields (MF) may affect the health of workers in an occupational environment. However, there is no clear evidence that the emission of MF from the visual display terminals (VDT) affects workers'mental status or induces stress in office environments. The purpose of our study was to investigate whether exposure to the MF during VDT work affects mental fatigue or induces stress related to psycho-physiological changes in workers. Thirty-seven students were voluntarily recruited to participate in this study. We created experimental conditions that a pair of the liquid crystal display (LCD) terminals separated by screens was closely placed in front of the visual suface of the cathode ray tube (CRT) units. All participants were not able to recognize whether the power of the CRT Units was ON or OFF while they worked with the LCD terminals. When the CRT unit was ON, participants who worked with the LCD terminal were called CRT-ON group. On the other hand, when the CRT unit was OFF, participants who worked with the CLD terminal were called CRT-OFF group. Incredibly short profiles of mood states (ISP)and subjective symptom questionnaires were used as indices of the mental fatigue as well as psychological stress before and after VDT work. Furthermore, salivary chromogranin A and urinary 8-hydroxydeoxyguanosine (8-OH-dG) were collected to measure physiological changes before and after VDT work. The results of the questionnaires and salivary and urinary stress markers showed that the exposure to the MF during VDT work did not significantly induce mental fatigue or psychological stress in comparison with the CRT-OFF group. Contrary to the results from the exposure, mood states of vigor decreased greatly (P < 0.05) whereas the states of fatigue and confusion increased significantly (P < 0.001) after VDT work. In the questionnaires for subjective symptoms, participants complained remarkably regarding 14 out of 25 conditions after VDT work. Moreover, urinary 8-OH-dG excretion increased significantly after VDT work. Taken together, the results of this study did not detect any bad health effects of MF exposure on the VDT participants but suggested that VDT work itself affects their mental fatigue and psycho-physiological status.
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PMID:A very low level of magnetic field exposure does not affect a participant's mental fatigue and stress as much as VDT work. 1579 90

The effects of mental fatigue on attention were assessed. Subjects performed a visual attention task for 3 h without rest. Subjective levels of fatigue, performance measures and EEG were recorded. Subjective fatigue ratings, as well as theta and lower-alpha EEG band power increased, suggesting that the 3 h of task performance resulted in an increase in fatigue. Reaction times, misses and false alarms increased with time on task, indicating decreased performance efficiency in fatigued subjects. Subjects were unable to inhibit automatic shifting of attention to irrelevant stimuli, reflected by a larger negativity in the N1 latency range for irrelevant, compared to relevant stimuli. This difference in negativity was unaffected by time on task. However, N1 and N2b amplitude did change with time on task: N1 amplitude decreased, and the difference in N2b amplitude between relevant and irrelevant stimuli (larger N2b amplitude evoked by relevant stimuli) decreased with time on task. The results indicate a dissociation in the effects of mental fatigue on goal-directed (top-down) and stimulus-driven (bottom-up) attention: mental fatigue results in a reduction in goal-directed attention, leaving subjects performing in a more stimulus-driven fashion.
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PMID:Effects of mental fatigue on attention: an ERP study. 1591 65

Focusing of attention is influenced by external features such as the presence of global or local target stimuli, but also by motivation and mood states. In the current study, we examined whether working on cognitively demanding tasks for 2 h, which induces mental fatigue, subsequently had a differential effect on global and local processing. The results showed that, compared to non-fatigued participants, fatigued participants particularly displayed compromised local processing. This indicates that mental fatigue may also manifest itself as effects on attentional focusing. The findings of this study are in line with recent ideas about the nature of fatigue-related cognitive deficits, implying disturbances in the control over attention and behaviour.
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PMID:Mental fatigue disturbs local processing more than global processing. 1596 53

This study was devised to evaluate the influence of muscle fatigue on athletes' ability to perform motor imagery. Performance impairment is a consequence of fatigue, but alterations on perception and mental activity may also occur. To test whether peripheral fatigue affects mental processes, ten sports students imagined three consecutive countermovement jumps before and after a fatiguing protocol, through repetition of upright movements, at 70% of maximal voluntary contraction, until exhaustion. Autonomic nervous system responses and imagined movement durations were considered the dependent variables. Actual duration was systematically overestimated during both visual and kinesthetic imagery, but motor imagery duration and autonomic responses were similar without and under fatigue. Results suggest that muscle fatigue, unlike fatigue induced by prolonged exercise, does not elicit mental fatigue and therefore does not alter motor imagery accuracy.
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PMID:Effect of a fatiguing protocol on motor imagery accuracy. 1600 36

Fatigue can be defined as a subjective state of an imbalance in the availability of inner resources needed to perform physical or mental activities. The level of fatigue is determined not only by the availability of inner resources but also by the demands of the activities performed. Most conventional fatigue scales require subjects to rate their level of fatigue without specifying the situation. In the present study, we constructed a subjective rating scale, the Situational Fatigue Scale (SFS), with which subjects estimated their level of fatigue in specific activities of daily life. We administered the SFS, along with the Fatigue Assessment Instrument (FAI) to 96 outpatients in a family-medicine clinic and to 62 college students to assess the psychometric properties of the SFS. Principle component analysis revealed two underlying factors: physical fatigue and mental fatigue. SFS scores were significantly correlated with several FAI scores and differentiated patients complaining of fatigue from those who did not. The SFS also showed good internal consistency and test-retest reliability. These results suggest that the SFS could be a useful tool to measure a different dimension of the broad concept of fatigue.
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PMID:The situational fatigue scale: a different approach to measuring fatigue. 1604 10

Long hours of continuous, mental task reportedly increase the average auditory P3 latency of the normal subjects significantly, a change that is thought to be related to mental fatigue. We have tried out several protocols of varying task difficulty and duration in an effort to study the onset of the assumed fatigue-related changes. The present study shows that changes in visual event-related potential occur in less than two minutes if the task is sufficiently rigorous. The changes occur both in latency and in amplitude. Moreover, the changes are reversible with a brief (30 second) period of hyperventilation. The changes were most marked at Fz. Following the difficult task, the P3 amplitude at Fz decreased from 8.588 micro/V +/- 0.966 to 5.800 microV +/- 0.795 and the P3 latency increased from 368 +/- 4 ms to 380 +/- 3. Following hyperventilation, the P3 amplitude at Fz reverted to 8.457 +/- 5 and the P3 latency reverted to 371 +/- 5 ms. These observations call for further investigations on the cause of the post-task changes and their quick reversibility.
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PMID:Post-task changes in visual P300 and their reversibility through brief hyperventilation. 1617 Sep 92

In this study we examined whether the effects of mental fatigue on behaviour are due to reduced action monitoring as indexed by the error related negativity (Ne/ERN), N2 and contingent negative variation (CNV) event-related potential (ERP) components. Therefore, we had subjects perform a task, which required a high degree of action monitoring, continuously for 2h. In addition we tried to relate the observed behavioural and electrophysiological changes to motivational processes and individual differences. Changes in task performance due to fatigue were accompanied by a decrease in Ne/ERN and N2 amplitude, reflecting impaired action monitoring, as well as a decrease in CNV amplitude which reflects reduced response preparation with increasing fatigue. Increasing the motivational level of our subjects resulted in changes in behaviour and brain activity that were different for individual subjects. Subjects that increased their performance accuracy displayed an increase in Ne/ERN amplitude, while subjects that increased their response speed displayed an increase in CNV amplitude. We will discuss the effects prolonged task performance on the behavioural and physiological indices of action monitoring, as well as the relationship between fatigue, motivation and individual differences.
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PMID:Mental fatigue, motivation and action monitoring. 1628 51


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