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

We monitored 15 healthy young adults during 18 hours of sleep deprivation. Subjects were repeatedly tested on measures of the P300 (P3) event-related potential, reaction time, body temperature, and a subjective rating of fatigue. Statistically significant decreases in P3 amplitude (P < or = .01) and increases in P3 latency (P < or = .0001) were found during sleep deprivation. These changes correlated with body temperature and fatigue and were not due to circadian variation. Reaction time did not show a significant change over time. We conclude that the P3 potential is a more sensitive cognitive measure of sleep deprivation than reaction time, a measure commonly used in previous studies. We provide a review of the literature on the P3 and recommend the use of the P3 as a marker to examine sleep deprivation in health professionals.
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PMID:The P300 event-related potential. The effects of sleep deprivation. 146 82

Hormones of the pituitary-adrenocortical axis (e.g., cortisol) are involved in the regulation of brain function. This study was aimed to clarify whether individual differences in baselines of cortisol are related to differences in heart rate (HR), slow brain potential shifts (SPS), performance data and personality. 17 males were instructed to solve 120 arithmetical tasks under time stress conditions. They could obtain monetary bonuses according to the accuracy of their task performance. This test condition was compared to a control condition. To determine the plasma level of cortisol by radioimmunoassays four blood samples were collected during the session. Baselines were estimated twice. A clustering procedure with respect to all cortisol levels resulted in a group of high responders (HC, n = 9) and a group of low responders (LC, n = 8). The HR was significantly higher in the HC group. The SPS of the LC group were characterized by a larger P300 elicited by the task followed by a steep negative slow wave (NSW) as compared to the HC group. LC subjects also showed a higher NSW before feedback presentation. The LC group solved the tasks faster and obtained more than twice the reward than the other group. They scored higher in achievement motivation and also reported increased 'Social Acceptance' and decreased 'Tiredness'. In sum, the results suggest a more efficient regulation of the arousal level of the LC group in contrast to the HC group as far as reflected in the parameters analysed.
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PMID:Differences in mental task performance and slow potential shifts in subjects differing in cortisol level. 152 27

Perception of hunger and satiety was examined by means of event-related potential (ERP) recordings. On the basis of Helson's frame-of-reference theory, it was hypothesized that hunger is perceived with reference to an actual adaptation level. ERPs were recorded to adjectives (hungry, thirsty, tired) combined with one of five adverbs (very, almost, somewhat, hardly, not). Subjects indicated whether a particular adverb-adjective combination accurately described their actual feeling of hunger, thirst, or fatigue. They were tested after they had fasted for 16 hr and another time when they were satiated. Area of P300 of the ERP was smallest for adverb-adjective combinations agreeing with the subject's actual state of hunger (i.e., adaptation level), which was almost hungry in fasting subjects and hardly hungry in satiated subjects. These P300 minima were flanked by significantly enhanced (p < 0.001) P300 areas for the immediately adjacent adverbs combined with hungry. P300 areas for adverbs combined with thirsty and tired did not depend on the subject's state of hunger. The data suggest that perception of internal states, such as hunger, refers to an adaptation level that is sensitively indicated by P300 area.
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PMID:Event-related brain potential correlates of self-reported hunger and satiety. 841 58

The P300 event-related brain potential (ERP) is thought to reflect neuroelectric activity related to cognitive processes such as attention allocation and activation of immediate memory. However, recent studies have provided evidence that the P300 also is influenced by biological processes such as fluctuations in the arousal state of subjects. The effects of natural (circadian, ultradian, seasonal, menstrual) and environmentally induced (exercise, fatigue, drugs) state variables on the P300 are reviewed. The findings suggest that these factors contribute to P300 measures and are discussed in terms of their theoretical and applied implications.
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PMID:Cognitive and biological determinants of P300: an integrative review. 853 88

The purpose of this study was to assess the relationship between mental fatigue and event-related potentials (ERPs). Six healthy men (mean age: 22 years old) performed a simple calculation for 6 h. Auditory ERPs were recorded before and after the calculating task. The scores of subjective fatigue symptoms were significantly increased, and P300 latency of auditory ERPs was significantly prolonged by the calculating task (P<0.05). We suggest that the recording of ERPs may be useful for the objective evaluation of mental fatigue.
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PMID:Objective evaluation of fatigue by event-related potentials. 966 85

The reduction of long-latency auditory ERPs amplitude, including P300, to repeated stimuli has been well documented in the literature on habituation. The effect of block repetition on auditory ERPs recorded for clinical purposes, where interblock intervals are commonly longer than those employed in habituation studies, was studied in a sample of 38 adults submitted to two blocks of a counting oddball paradigm. Four different experimental conditions were considered, differing in target probability, delivery or not of a previous passive oddball tone sequence, and the performance or not of other oddball tasks requiring more complex discriminative responses between the two blocks. Results showed that: (1) N1 amplitude to the frequent non-target stimuli decreased in the second block under all the conditions; (2) when the two blocks were consecutive (separated by 2-3 min), P300 amplitudes were unaffected by block repetition, this whatever the probability of the target (25% vs. 10%) and whether or not a passive oddball sequence preceded the two active blocks; (3) P300 amplitude was only affected by stimulus repetition in those subjects who performed more complex cognitive tasks between the first and second blocks and; (4) latency values were unaffected by repetition. It is hypothesised that the N1 amplitude decline may be caused by a decrease in alertness or arousal level produced by stimuli repetition. Reduction in P3 amplitude only appeared when more difficult tasks had to be done between the two oddball blocks and may reflect a decrease in the amount of attentional resources allocated to the second block, due either to fatigue or over training. The practice of using a grand average of several repetitions of the oddball paradigm, as recommended for the clinical use of long-latency ERPs, seems to be adequate provided that long interblock intervals are used and that the subject is not engaged in tasks requiring a high mental workload between the trial blocks.
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PMID:On the validity of interblock averaging of P300 in clinical settings. 1057 95

Diurnal variation in the P300 component of the human cognitive event-related potential (ERP) was examined. The P300 component is considered to be a measure of neuroelectric activity related to cognitive functions such as attention allocation and information processing. Nine diurnally active healthy male subjects whose sleep-wake rhythms were synchronized prior to the experiment were studied. The P300 components oral temperature, heart rate, left- and right-hand grip strength, reaction time, subjectively rated sleepiness, attention level, and fatigue were measured at 08:00, 11:00, 14:00, 17:00, and 20:00. Significant diurnal variations in P300 latency, P300 amplitude, oral temperature, heart rate, left- and right-hand grip strength, subjectively rated sleepiness, and attention level were observed. The P300 latency at 08:00 was significantly longer than at 11:00, 17:00, and 20:00, while the P300 amplitude at 08:00 was significantly greater than at 17:00 and 20:00. The P300 latency was correlated positively with subjectively rated sleepiness and negatively correlated with subjectively rated attention level. These results suggest the existence of diurnal variation in human cognitive functions.
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PMID:Diurnal variation in the P300 component of human cognitive event-related potential. 1102 14

The effects of the human immunodeficiency virus (HIV) infection on the central nervous system function were studied with electroencephalographic (EEG) and auditory event-related brain potentials (EPRs) in patients infected with HIV and unaffected young adult control subjects (n=10/group). All subjects were assessed once every 15 min for four trial blocks at the same time of day to assess EEG/ERP changes with time on task-induced fatigue. Spectral analysis was applied to the pre- and post-stimulus EEG segments. ERP values were evaluated with respect to group differences for component amplitude and latency measures. Spectral analysis demonstrated that HIV patients evinced greater pre-stimulus delta power over frontal areas compared to control subjects, and less post-stimulus spectral power for the delta, theta, and alpha bands over the central/parietal areas. P300 amplitude was smaller, and latency was marginally longer for the HIV patients compared to control subjects. P300 latency correlated positively with increases in the patient HIV viral load. Time-on-task generally did not affect EEG or ERP measures for either group other than contributing to an overall decrease in neuroelectric responsivity. Group spectral power effects were consistent with differences in arousal/fatigue level. P300 group differences were consistent with declines in cognitive capability, and P300 latency increased with increased viral load. HIV infection negatively affected central nervous system function as measured by EEG and cognitive ERPs in a manner that suggests decreased arousal and increased fatigue in HIV patients.
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PMID:Neuroelectric assessment of HIV: EEG, ERP, and viral load. 1102 97

The relationships among stimulus relevance and the position of target stimuli in a sequence with the P300 component of event related brain potentials and reaction time were investigated. An auditory oddball series was presented to 42 healthy, young, right-handed female participants. In the series, participants were to ignore the standard stimuli and count the deviants from 1 to 6. When reaching the count of 6, they had to restart their count from 1 again. While counting, half of the sample had to press a key after the deviants, numbers 1, 2 and 3, but not after the numbers 4, 5 and 6. The other half of the sample had to press the key when numbers 4, 5 and 6 rather than when numbers 1, 2, 3 appeared. The P300 amplitude of the more relevant (count and press) stimuli was higher than that of the P300 amplitude of the less relevant (count only) stimuli. This is associated with a greater allocation of cognitive resources to the more relevant stimuli. An interaction was also found between the position of the target stimuli in a sequence and the stimulus relevance, which is attributed to the cognitive preparation. Furthermore, the reaction time tended to increase along the sequence of the more relevant stimuli, due perhaps to an increase in physical fatigue.
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PMID:Effect of the relevance and position of the target stimuli on P300 and reaction time. 1123 96

For clinical use of event-related potentials (ERPs), issues to be solved included individual variations in their latencies and amplitudes, inconsistencies in the abnormalities of these parameters in dementia patients among research institutes, etc. In normal groups, variations in the latency and amplitude of P300 (P3), a representative ERP component, can be resolved by the standardization of several of its biological determinants. The determinants included 1) natural factors, e.g. circadian rhythm, the season, 2) induced factors, e.g. exercise, fatigue, drugs, and 3) constitutional factors, e.g. age, sex. The inconsistency of data among dementia patients is mostly due to differences in the severity or stage of dementia. However, clinically the most important issue is to develop an ERP test to identify mild cognitive dysfunction at an early stage of dementia, which differs from that at an advanced stage. For example, in familial Alzheimer's disease, a test for verbal memory is reported to be the most sensitive. On the other hand, mismatch negativity, one of the early ERP components, is a pre-attentive automatic response to changes in auditory stimuli. Since this component can be evoked without any attention or task, one of its advantages is that it can be recorded in infants or small children, or in demented or comatose patients. Other clinically useful ERP components are also introduced.
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PMID:[Clinically useful event-related potentials]. 1223 29


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