Non-fatigued Participants Research Articles

Physical Activity and Sedentary Behavior Timing in Fatigued and Nonfatigued Adults With Multiple Sclerosis

ObjectiveTo examine device-measured physical activity levels and sedentary behavior participation during different times of the day (ie, morning, midday, and evening) in adults with multiple sclerosis (MS) who differed in fatigue status. DesignCross-sectional survey. SettingRemote survey study managed by a university-based research laboratory. ParticipantsA population-based sample of 1000 participants with MS were sent recruitment materials by the North American Research Committee on Multiple Sclerosis and 218 participants completed all relevant outcomes (N=218). InterventionsNot applicable. Main Outcome MeasuresParticipants (N=218) completed the Fatigue Severity Scale (FSS) as a measure of fatigue severity and were divided into subgroups of fatigued (FSS score ≥4) and nonfatigued (FSS score <4). Participants wore an ActiGraph GT3X+ on the nondominant hip for 7 days to measure physical activity (ie, light physical activity [LPA], moderate-to-vigorous physical activity [MVPA], steps) and sedentary behavior. ResultsFatigued participants engaged in less MVPA (F[1216]=18.5, P<.001), fewer steps (F[1216]=27.8, P<.001), and more sedentary time (F[1216]=8.2, P=.005) than nonfatigued participants. Regardless of group, the highest levels of LPA (F[1.7355.7]=72.9, P<.001) and MVPA (F[1.8395.3]=23.0,P<.001) occurred in the morning and middle of the day, with the lowest levels in the evening. Regardless of group, the highest levels of sedentary behavior occurred in the evening, with similar levels in the morning and evening (F[1.6354.5]=84.3,P<.001). Regardless of group, participants had more steps in the middle of the day, followed by morning and then evening (F[1.8383.9]=84.7,P<.001). ConclusionsOur results suggest that physical activity timing should be considered in future development and delivery of behavior interventions that focus on increasing physical activity and reducing sedentary behavior among adults with MS who have fatigue.

Post-stroke fatigue is associated with resting state posterior hypoactivity and prefrontal hyperactivity.

Fatigue is associated with poor functional outcomes and increased mortality following stroke. Survivors identify fatigue as one of their key unmet needs. Despite the growing body of research into post-stroke fatigue, the specific neural mechanisms remain largely unknown. This observational study aimed to identify resting state brain activity markers of post-stroke fatigue. Sixty-three stroke survivors (22 women; age 30-89 years; mean 67.5 ± 13.4 years) from the Cognition And Neocortical Volume After Stroke study, a cohort study examining cognition, mood, and brain volume in stroke survivors following ischemic stroke, underwent brain imaging three months post-stroke, including a 7-minute resting state functional magnetic resonance imaging. We calculated the fractional amplitude of low-frequency fluctuations, which is measured at the whole-brain level and can detect altered spontaneous neural activity of specific regions. Forty-five participants reported experiencing post-stroke fatigue as measured by an item on the Patient Health Questionnaire-9. Fatigued compared to non-fatigued participants demonstrated significantly lower resting-state activity in the calcarine cortex (p < 0.001, cluster-corrected pFDR = 0.009, k = 63) and lingual gyrus (p < 0.001, cluster-corrected pFDR = 0.025, k = 42) and significantly higher activity in the medial prefrontal cortex (p < 0.001, cluster-corrected pFDR = 0.03, k = 45). Post-stroke fatigue is associated with posterior hypoactivity and prefrontal hyperactivity reflecting dysfunction within large-scale brain systems such as fronto-striatal-thalamic and frontal-occipital networks. These systems in turn might reflect a relationship between post-stroke fatigue and abnormalities in executive and visual functioning. This whole-brain resting-state study provides new targets for further investigation of post-stroke fatigue beyond the lesion approach.

The Role of Gut Microbiome Perturbation in Fatigue Induced by Repeated Stress from Chemoradiotherapy: A Proof of Concept Study.

Objectives The objectives of this proof of concept study were to (a) examine the temporal changes in fatigue and diversity of the gut microbiome over the course of chemoradiotherapy (CRT) in adults with rectal cancers; (b) investigate whether there are differences in diversity of the gut microbiome between fatigued and nonfatigued participants at the middle and at the end of CRT; and (c) investigate whether there are differences in the relative abundance of fecal microbiota at the phylum and genus levels between fatigued and nonfatigued participants at the middle and at the end of CRT. Methods Stool samples and symptom ratings were collected prior to the inception of CRT, at the middle (after 12–16 treatments) and at the end (after 24–28 treatments) of the CRT. Descriptive statistics and Mann–Whitney U test were computed for fatigue. Gut microbiome data were analyzed using the QIIME2 software. Results Participants (N = 29) ranged in age from 37 to 80 years. The median fatigue score significantly changed at the end of CRT (median = 23.0) compared with the median score before the initiation of CRT for the total sample (median = 17.0; p ≤ 0.05). At the middle of CRT, the alpha diversity (abundance of Operational Taxonomic Units) was lower for fatigued participants (149.30 ± 53.1) than for nonfatigued participants (189.15 ± 44.18, t(23) = 2.08, p ≤ 0.05). At the middle of CRT, the alpha diversity (abundance of Operational Taxonomic Units) was lower for fatigued participants (149.30 ± 53.1) than for nonfatigued participants (189.15 ± 44.18, Proteobacteria, Firmicutes, and Bacteroidetes were the dominant phyla for fatigued participants, and Escherichia, Bacteroides, Faecalibacterium, and Oscillospira were the most abundant genera for fatigued participants. Conclusion CRT-associated perturbation of the gut microbiome composition may contribute to fatigue.

Fatigue increases the perception of future effort during decision making

ObjectivesWhen making a decision, humans and other animals consider both the value of the alternatives and their associated effort. Accordingly, several studies have shown that the value-functions of rewards decrease proportionally to the effort required to secure them (effort-discounting). Nevertheless, it is unclear whether and how the momentary physiological condition of the body (e.g., fatigue) influences cost-benefit computations and the evaluation of future prospects. DesignParticipants were asked to make a series of effort-based choices between two different effort-demanding monetary outcomes, which varied both in reward magnitudes (money) and effort (time to be spent cycling on a bicycle ergometer at submaximal performance of ∼70% of Vo2max after the experimental session). The tests were performed in two conditions: when participants were fatigued versus not fatigued. MethodsVisual presentation of the choice alternatives and recordings of the subjects’ responses were performed using the Mouse Tracker software, which allowed the recording of the kinematics of the mouse movements associated with the choice of 20 human subjects. ResultsOur findings show that fatigued participants increased their preference for less-costly offers, which indicates effort-discount (i.e., decrease of participants' value functions). Kinematic analysis of participants' choices revealed the dynamical signature of this preference shift: while non-fatigued participants had a strong initial bias for the higher-value, higher-effort choice offer, this bias lacked in fatigued participants. ConclusionsOur results suggest that increased fatigue levels may “scale up” effort-costs, counteracting the (otherwise default) choice of higher-valued offers. These results are relevant for the ongoing debate on whether and why fatigue impairs athletes’ ability to select actions optimally.

Effect of fatigue on laparoscopic skills: a comparative historical cohort study

Fatigue has been shown to have a negative impact on surgical performance. However, there is a lack of research investigating its effect on laparoscopy, particularly in Australia. This study investigated whether fatigue associated with a surgeon's usual workday led to a measurable drop off in laparoscopic surgical skills as assessed on a laparoscopic simulator. A comparative study involving two cohorts was undertaken: a study group whose data were collected prospectively was compared to a historical control group. Participants were required to reach a predetermined level of proficiency in each laparoscopic task on either a FLS or LapSim simulator. The participants in the study cohort were re-tested approximately 1 month after completing 10 h of work. The participants in the historical non-fatigued group were re-tested approximately 1 month after reaching proficiency. Comparisons between cohorts were made using a 'decrease in score per day elapsed' value to account for the natural attrition in skills over time and the variability in testing times within and between the two cohorts. The decrease in overall score per day elapsed for fatigued participants was significantly greater than for historical non-fatigued participants, irrespective of the simulator type. Fatigue had a greater impact on certain laparoscopic skills, including peg transfer and knot tying. Participants who self-reported higher level of fatigue demonstrated significantly better skills than those who self-reported lower levels. Overall laparoscopic skill proficiency was reduced in the fatigued participants compared to the historical non-fatigued participants, with certain laparoscopic skills more affected than others.

Association of C-reactive protein and interleukin-6 with new-onset fatigue in the Whitehall II prospective cohort study

Although basic research on neuroimmune interactions suggests that inflammatory processes may play a role in the development of fatigue, population-based evidence on this association is limited. This study examined whether plasma C-reactive protein (CRP) and interleukin-6 (IL-6), biomarkers of systemic inflammation, predict fatigue onset. The Whitehall II study is a large-scale cohort study conducted in 20 civil service departments in London. Plasma CRP and IL-6 were measured in 4847 non-fatigued participants at phase 3 (1991-1993, aged 39-63 years). Fatigue was assessed using the Vitality subscale of the 36-item Short Form Health Survey (SF-36) at phase 3 and phase 4 (1995-1996). During a mean follow-up of 3.1 years, 957 new fatigue cases (19.7%) were identified using the pre-established cut-off score of ≤ 50 on the Vitality subscale. CRP values were dichotomized as low (<1.0 mg/l ) or high (≥ 1.0 mg/l) using the Centers for Disease Control/American Heart Association recommendations. Similarly, IL-6 values were also dichotomized as low (<1.5 pg/ml) or high (≥ 1.5 pg/ml). After full adjustment for sociodemographic and biobehavioral covariates, the odds ratios for new-onset fatigue were 1.28 [95% confidence interval (CI) 1.09-1.49, p = 0.003] for high CRP and 1.24 (95% CI 1.06-1.45, p = 0.008) for high IL-6. Similar results were found when CRP and IL-6 were treated as continuous variables. Plasma CRP and IL-6 were prospectively associated with new-onset fatigue, supporting the hypothesis that low-grade inflammation has a role in the development of fatigue.

Maximal exercise performance in patients with postcancer fatigue

The aim of this study is to examine whether physical fitness of severely fatigued and non-fatigued cancer survivors, as measured by maximal exercise performance, is different between both groups and, if so, whether this difference can be explained by differences in physical activity, self-efficacy regarding the exercise test, and/or social support. Severely fatigued (n = 20) and sex- and age-matched non-fatigued (n = 20) disease-free cancer survivors, who completed treatment for a malignant, solid tumor at least 1 year earlier, participated in this case-control study. Maximal oxygen consumption was measured during an incremental cycling exercise test. Physical activity was assessed via actigraphy. Self-efficacy regarding the test and social support were assessed via questionnaires to study its relationship with physical fitness. Maximal oxygen consumption was significantly lower in fatigued compared to non-fatigued participants. Actual physical activity, self-efficacy regarding the test, and negative interactions of social support were significantly different between both groups. However, after inclusion of these three variables in linear regression analyses, the difference in physical fitness between fatigued and non-fatigued cancer survivors persisted. Maximal oxygen consumption, a measure for physical fitness, was reduced in severely fatigued compared to non-fatigued cancer survivors. The inferior maximal exercise performance cannot fully be explained by differences in physical activity, self-efficacy, or social support between both groups. Other currently still unknown factors, such as a disturbance in the cardiopulmonary circuit, may play a role.

Structural and functional MRI of the brain as biomarker for postcancer fatigue.

9050 Background: Fatigue after curative cancer treatment is a frequently occurring problem, impairing quality of life. Little is known about physiological factors determining postcancer fatigue. We aim to assess if structural and/or functional magnetic resonance imaging (MRI) of the brain can be used as a biomarker for postcancer fatigue. Methods: Severely fatigued (n=25) and matched non-fatigued (n=16) disease-free cancer survivors, who completed treatment of a malignant tumor ≥1 year earlier, participated in this case-control study. Patients with a brain tumor were excluded. Structural MRI was performed on a 3T MR system and segmentation of the brain into gray matter (GM) and white matter (WM) was carried out using a voxel-based morphometry method. Volumes of hippocampus and thalamus were obtained using FMRIB Software Library (FSL FIRST). Functional MRI by magnetic resonance spectroscopic imaging (MRSI) at 3T was used to measure N-acetylaspartate (NAA) levels in the hippocampus and the ratio of choline to creatine (Cho:Cr) in the occipital cortex. LCModel was used to analyze the 1H-spectra. One-way ANOVA was performed and differences were considered statistically significant at p<0.05. Results: Volumetry results (Table) showed a significantly smaller volume of the thalamus (p=0.015) in fatigued compared to non-fatigued cancer-survivors. Other MR(S)I parameters were not significantly different between severely fatigued and non-fatigued participants (Table). Conclusions: Thalamus volume was significantly smaller in fatigued compared to non-fatigued cancer-survivors. As non-motor functions of the basal ganglia play a key role in central fatigue, the thalamus, which interacts with the basal ganglia, may also contribute to fatigue. Thus, thalamus volume may serve as a possible biological marker for postcancer fatigue. MR(S)I results. Structure Severely fatigued Non-fatigued GM 689.133 ± 75.857 ml 663.414 ± 61.457 ml WM 526.633 ± 89.716 ml 496.485 ± 64.695 ml Hippocampus 0.445 ± 0.042 % of TBV 0.464 ± 0.048 % of TBV Thalamus 0.885 ± 0.050 % of TBV 0.929 ± 0.056 % of TBV Hippocampus [NAA] 8.60 ± 0.76 mmol l-1 8.97 ± 0.99 mmol l-1 Occipital cortex (Cho/Cr) 1.09 ± 0.30 peak intensity 1.03 ± 0.21 peak intensity Abbreviation: TBV, total brain volume.

Clinical, laboratory, and neuroimaging characteristics of fatigue in HIV-infected individuals

Fatigue is among the most common symptoms reported by HIV-infected individuals. Previous reports suggest that the prevalence of fatigue varies by disease status with rates close to 80% in patients with AIDS. However, most studies have not been conducted in the setting of a controlled trial and have not assessed the association of fatigue with cellular markers of brain activity. Data for this study were derived from baseline and longitudinal evaluations in ACTG A5090, a randomized, double-blind, placebo-controlled trial of the Selegiline Transdermal System for the treatment of HIV-associated cognitive impairment. Fatigue was assessed using the Fatigue Severity Scale with scores of >4 considered "fatigued". Participants in a substudy underwent brain magnetic resonance spectroscopy (MRS) imaging, an in vivo method for assessing brain metabolites associated with neuronal and glia activity. Differences between fatigued and non-fatigued participants were evaluated with respect to demographics and clinical characteristics, plasma and CSF HIV-1 RNA concentration, CD4 counts, and brain metabolites. One hundred and twenty-eight participants were enrolled (88% male, median age = 45 years) and 82 participants (64%, 95% confidence interval 55%, 72%) were fatigued at baseline. MRS was conducted in 62 of the 128 participants. Fatigued participants were significantly younger (p = 0.011), had lower Karnofsky scores (p = 0.032), and had higher levels of depressive symptoms on the Center for Epidemiologic Studies Depression (CES-D) scale (p < 0.001) than non-fatigued participants. Statistically significant differences between fatigued and non-fatigued groups were not detected for plasma and CSF HIV-1RNA concentration, CD4 counts, or on neuropsychological tests. MRS revealed significantly lower levels of the cellular energy marker total creatine (p = 0.002) in the basal ganglia of fatigued participants. Statistically significant differences in other brain metabolites were not detected. Longitudinal data showed that fatigue persisted and worse fatigue at baseline was predictor of future fatigue. Among the cognitive tests, baseline Stroop score was associated with future fatigue. Fatigue was present in 64% of A5090 study participants and persisted during the 24 weeks of follow-up. Fatigue was associated with worse functional performance and depressive mood. Lower cellular energy levels in the basal ganglia, as measured by MRS total creatine concentration, suggest energy dysmetabolism in this brain region. This observation, taken together with the association between fatigue and neuropsychological tests of frontal lobe performance is consistent with the hypothesis of a striatal-cortical circuitry involvement in the symptoms of fatigue.

Deployment-related severe fatigue with depressive symptoms is associated with increased glucocorticoid binding to peripheral blood mononuclear cells

Severe fatigue and co-morbid depressive symptoms are frequently reported by recently deployed military personnel. Stress can induce lasting changes in the negative feedback regulation of the hypothalamic–pituitary–adrenal axis (HPA-axis) and the regulation of the immune system by cortisol. Since these actions of cortisol are modulated via glucocorticoid receptors (GR), we investigated the effect of deployment and of deployment-related fatigue on glucocorticoid binding to peripheral blood mononuclear cells (PBMCs) in a prospective design. Psychological assessments and blood sample collection took place before and one and six months after deployment. Participants were selected from a larger group and assigned to three groups based on their level of fatigue and depressive symptoms six months after deployment. We compared fatigued participants without depressive symptoms ( n = 21), fatigued participants with depressive symptoms ( n = 14) and non-fatigued participants without depressive symptoms ( n = 21). Fatigued participants with depressive symptoms at six months after deployment had higher glucocorticoid binding to PMBCs than the other two groups at all three time points. Notably, this difference was already present before deployment. There was no effect of deployment on glucocorticoid binding to PBMCs. The observed differences in glucocorticoid binding were not related to pre-existing group differences in psychological symptoms. No group differences were observed in the composition of the PBMC population and plasma cortisol levels. These results indicate that high glucocorticoid binding to PBMCs might represent a vulnerability factor for the development of severe fatigue with depressive symptoms after a sustained period of stress, such as deployment.

Predictors of Persistent and New-onset Fatigue in Adolescent Girls

The purpose of this study was to investigate the stability of fatigue in adolescents and to explore whether psychological, somatic, and lifestyle factors are involved in the onset and persistence of fatigue during adolescence. In this longitudinal study, a total of 653 adolescent girls (aged 14.40 +/- 1.45 years) who previously participated in an epidemiological study filled out questionnaires 6 (T2) and 12 (T3) months after the initial assessment (T1). Fatigue severity, depression, anxiety, and chronic fatigue syndrome-related symptoms were assessed. We determined the prevalence of severely fatigued cases at T2 and T3 and evaluated whether persistently fatigued participants initially differed from nonfatigued participants and participants with transient fatigue. We examined which factors predicted the development of new-onset fatigue and investigated whether changes in fatigue covaried with changes in other complaints and changes in lifestyle. Of all participants who were severely fatigued at T1, 25.7% were persistently fatigued throughout the study. Persistently fatigued participants had higher levels of depression and anxiety at the beginning of the study, were less physically active, and slept shorter. New-onset fatigue was predicted by depression, less physical activity, and more nightlife activities. Interestingly, new onset was not predicted by initial levels of fatigue. Persistently fatigued participants did not differ in initial fatigue severity from short-term fatigued patients. A decrease in fatigue severity was associated with a decrease in depression, anxiety, and chronic fatigue syndrome-related symptoms and, to a lesser extent, with an increase in physical activity and sleep duration. The stability of severe fatigue among adolescents is substantial. The involvement in the onset and persistence of fatigue suggests that both preventive and therapeutic strategies with respect to fatigue treatment in adolescents should concentrate on emotional well-being. Moreover, adolescents at risk should be stimulated to spend more time on physical activities and to sleep longer.

Glucocorticoid sensitivity of immune cells in severely fatigued adolescent girls: A longitudinal study

Fatigue during adolescence is associated with somatic and psychological complaints that resemble the pattern of symptoms described for chronic fatigue syndrome (CFS). Studies in CFS and other stress-related syndromes suggested a dysfunction of the interactions between the hypothalamic-pituitary-adrenal axis (HPA-axis) and the immune system, i.e. a changed glucocorticoid (GC) receptor sensitivity of immune cells, to exist. Here we investigated whether severely fatigued girls from a healthy population have altered cortisol production and immune cell sensitivity for the synthetic GC, dexamethasone (DEX). In a longitudinal design, we examined ex vivo DEX sensitivity of monocytes and of T-cell mitogen-induced responses of severely fatigued (N=65) and non-fatigued girls (N=60). Fatigued girls reported more severe comorbid complaints than non-fatigued participants across three measurements during 1 year (T1: spring, T2: autumn, T3: spring) and had higher plasma cortisol levels throughout the study. DEX sensitivity of T-cell mitogen-induced responses showed seasonal variation with increased sensitivity in autumn compared to spring. No systematic variation of monocyte glucocorticoid receptor (GR) sensitivity was observed. Significant rank correlations of DEX sensitivity of T-cell mitogen-induced responses between the three assessments during the year suggest a stable trait of immune function. Groups did not differ in DEX sensitivity on any of the read outs. However, in a persistently fatigued subgroup, sensitivity to DEX was significantly reduced on the level of interferon (IFN)-gamma production. These results show that although fatigued participants had severe (comorbid) complaints, only in the case when symptoms persisted, altered GC sensitivity of immune cells was observed.

Longitudinal analysis of pro- and anti-inflammatory cytokine production in severely fatigued adolescents

In the adolescent population, fatigue is associated with somatic complaints, unrefreshing sleep, cognitive disturbances and symptoms of depression and anxiety. This pattern of symptoms resembles the one described in chronic fatigue syndrome (CFS). Since immunological alterations have been reported in CFS patients, we wondered whether also severely fatigued girls from a healthy population would show comparable alterations in psychological and immunological parameters. We tested this hypothesis in a longitudinal design, allowing a reliable assessment of the participants’ characteristic immune status. Groups of severely fatigued ( N = 67) and non-fatigued ( N = 61) participants were selected. Severely fatigued girls reported more depressive symptoms, anxiety, reduced sleep quality, and somatic and CFS-related symptoms than non-fatigued participants across three measurements during one year (T1: spring, T2: autumn, T3: spring). In contrast, no group differences in mitogen-induced cytokine production or T-cell proliferation in vitro or in leukocyte subset counts were observed. Although absolute cytokine production and cell counts were affected by seasonal variation, the within-subject values, relatively to the rest of the participants, were fairly stable. Data from a small group of CFS patients ( N = 11) showed similarities in self-reported complaints between CFS patients and fatigued participants. Interestingly, CFS patients showed a distinct immune profile when compared to the severely fatigued or non-fatigued participants, i.e. increased levels of anti-inflammatory cytokines (IL-10, decreased IFN-γ/IL-10 ratio) and reduced levels of pro-inflammatory cytokines (IL-6, TNF-α) over all three time points analyzed. These results show that, although overlap in symptomatology between the general population and patients with CFS was observed, only CFS patients show a skewing of the cytokine balance towards an anti-inflammatory profile.

Complementary and alternative medical therapy utilization by people with chronic fatiguing illnesses in the United States

BackgroundChronic fatiguing illnesses, including chronic fatigue syndrome (CFS), pose a diagnostic and therapeutic challenge. Previous clinical reports addressed the utilization of health care provided to patients with CFS by a variety of practitioners with other than allopathic training, but did not examine the spectrum of complementary and alternative medicine (CAM) therapies used. This study was designed to measure CAM therapy use by persons with fatiguing illnesses in the United States population.MethodsDuring a random-digit dialing survey to estimate the prevalence of CFS-like illness in urban and rural populations from different geographic regions of the United States, we queried the utilization of CAM including manipulation or body-based therapies, alternative medical systems, mind-body, biologically-based, and energy modalities.ResultsFour hundred forty fatigued and 444 non-fatigued persons from 2,728 households completed screening. Fatigued subjects included 53 persons with prolonged fatigue, 338 with chronic fatigue, and 49 with CFS-like illness. Mind-body therapy (primarily personal prayer and prayer by others) was the most frequently used CAM across all groups. Among women, there was a significant trend of increasing overall CAM use across all subgroups (p-trend = 0.003). All categories of CAM use were associated with significantly poorer physical health scores, and all but one (alternative medicine systems) were associated with significantly poorer mental health scores. People with CFS-like illness were significantly more likely to use body-based therapy (chiropractic and massage) than non-fatigued participants (OR = 2.52, CI = 1.32, 4.82). Use of body-based therapies increased significantly in a linear trend across subgroups of non-fatigued, prolonged fatigued, chronic fatigued, and CFS-like subjects (p-trend = 0.002). People with chronic fatigue were also significantly more likely to use body-based therapy (OR = 1.52, CI = 1.07, 2.16) and mind-body (excluding prayer) therapy than non-fatigued participants (OR = 1.73, CI = 1.20 – 2.48).ConclusionUtilization of CAM was common in fatiguing illnesses, and was largely accounted for by the presence of underlying conditions and poor physical and mental health. Compared to non-fatigued persons, those with CFS-like illness or chronic fatigue were most likely to use body-based and mind-body therapies. These observations have important implications for provider education programs and development of intervention strategies for CFS.

Disrupted sensorimotor gating due to mental fatigue: Preliminary evidence

Mental fatigue is a common phenomenon that either results from sustained mental effort or that is comorbid to a range of psychological and somatic disorders. Important symptoms of mental fatigue comprise cognitive and attentional difficulties, which have adverse effects on task performance and on everyday activities. Yet, little is known about the neurocognitive mechanisms that underlie these effects. In the current study, we explore whether sensorimotor gating is one of the cognitive mechanisms that is disturbed under fatigue. To test this, we compare prepulse inhibition (PPI) between fatigued ( n = 11) and non-fatigued participants ( n = 9). Fatigue was induced by 90 min of cognitively demanding work. Results showed that, compared to the non-fatigue group, fatigued participants displayed significantly reduced levels of PPI after the manipulation. These findings are linked to theories about compromised cognitive control under fatigue and to recent ideas about the role of dopamine in fatigue as well as in the regulation of PPI.

Mental fatigue disturbs local processing more than global processing

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.

Mentale vermoeidheid en doelgericht handelen: effecten van taakcontext op de sturing van gedrag

Mental fatigue and goal-oriented behaviour: effects of task context on behaviour guidance Mental fatigue and goal-oriented behaviour: effects of task context on behaviour guidance Dimitri van der Linden, Gedrag &amp; Organisatie, Volume 17, August 2004, nr. 4, pp. 252-271. As mental fatigue is related to performance and safety, it has received considerable interest from researchers in work psychology. Nevertheless, much is unknown about the specific way fatigue affects task behaviour and performance. In the current article we argue that fatigue affects behaviour through a decreased impact of conscious goals and behavioural rules on choice of actions. This would manifest itself as a diminished cognitive flexibility and as difficulties in executing or initiating planning. We present two experiments in which we investigate whether fatigue-induced participants show less flexibility and planning than non-fatigued participants. In experiment 1 (n = 65), participants had to explore a computer application unfamiliar to them. In experiment 2 (n = 58) participants worked on standard neuropsychological tests that assessed flexibility and planning. The results of both experiments showed that, compared to the non-fatigued participants, fatigue participants were less flexible and displayed less effective or less efficient planning. These results support the idea of decreased influence of conscious goals and rules under fatigue. This conclusion has practical implications for as it may support the prediction and prevention of fatigue-related errors and accidents.