Subjective cognitive fatigue in multiple sclerosis depends on task length

Self-perceptual blindness to mental fatigue in mining workers

Mental fatigue is a psychophysiological state that adversely impacts performance in cognitive tasks, increasing risk of occupational hazards. Given its manifestation as a conscious sensation, it is often measured through subjective self-report. However, subjective measures are not always true measurements of objective fatigue. In this study, we investigated the relationship between objective and subjective fatigue measurements with the preventive AccessPoint fatigue assay in Chilean mine workers. Subjective fatigue was measured through the Samn-Perelli scale, objective fatigue through a neurocognitive reaction time task. We found that objective and subjective fatigue do not correlate (-0.03 correlation coefficient, p < 0.001). Moreover, severe fatigue cases often displayed absence of subjective fatigue coupled with worse cognitive performance, a phenomenon we denominated Perceptual Blindness to fatigue. These findings highlight the need for objective fatigue measurements, particularly in high-risk occupational settings such as mining. Our results open new avenues for researching mechanisms underlying fatigue perception and its implications for occupational health and safety.

Fatigue in multiple sclerosis: can we measure it and can we treat it?

Fatigue is a common and debilitating symptom in multiple sclerosis (MS). However, after over 100 years of inquiry its definition, measurement and understanding remains elusive. This paper describes the challenges clinicians and researchers face when assessing and treating MS patients, as well as our understanding of neural mechanisms involved in fatigue. Challenges for the future are discussed.

Prevalence and Associated Clinical Characteristics of Walking-Related Motor, Cognitive, and Fatigability in Progressive Multiple Sclerosis: Baseline Results From the CogEx Study

BACKGROUND

People with progressive multiple sclerosis (PMS) present motor (eg, walking) and cognitive impairments, and report fatigue. Fatigue encompasses fatigability which is objectively measured by the capacity to sustain a motor or cognitive task.

OBJECTIVE

To investigate the prevalence of walking and cognitive fatigability (CF) and the associated clinical characteristics in a large sample of PMS patients.

METHODS

PMS patients (25-65 years old) were included from 11 sites (Europe and North America), having cognitive impairment (1.28 standard deviation below normative data for the symbol digit modality test [SDMT]). Walking fatigability (WF) was assessed using the distance walk index (DWI) and CF using the SDMT (scores from the last 30 seconds compared to the first 30 seconds). Additional measures were: cognitive assessment-Brief International Cognitive Assessment for multiple sclerosis (MS), cardiorespiratory fitness, 6-minute walk, physical activity, depressive symptoms, perceived fatigue-Modified Fatigue Impact Scale (MFIS), MS impact-MSIS-29, and walking ability.

RESULTS

Of 298 participants, 153 (51%) presented WF (DWI = -28.9 ± 22.1%) and 196 (66%) presented CF (-29.7 ± 15%). Clinical characteristics (EDSS, disease duration, and use of assistive device) were worse in patients with versus without WF. They also presented worse scores on MSIS-29 physical, MFIS total and physical and reduced physical capacity. CF patients scored better in the MSIS-29 physical and MFIS psychosocial, compared to non-CF group. Magnitude of CF and WF were not related.

CONCLUSIONS

Half of the cognitively-impaired PMS population presented WF which was associated with higher disability, physical functions, and fatigue. There was a high prevalence of CF but without strong associations with clinical, cognitive, and physical functions.

TRIAL REGISTRATION NUMBER

The "CogEx-study," www.clinicaltrial.gov identifier number: NCT03679468.

Structural neural correlates of mental fatigue and reward-induced improvement in performance

Neuroimaging studies investigating the association between mental fatigue (henceforth fatigue) and brain physiology have identified many brain regions that may underly the cognitive changes induced by fatigue. These studies focused on the functional changes and functional connectivity of the brain relating to fatigue. The structural correlates of fatigue, however, have received little attention. To fill this gap, this study explored the associations of fatigue with cortical thickness of frontal and parietal regions. In addition, we aimed to explore the associations between reward-induced improvement in performance and neuroanatomical markers in fatigued individuals. Thirty-nine healthy volunteers performed the psychomotor vigilance task for 15 min (i.e., 3 time-on-task blocks of 5 min) out of scanner; followed by an additional rewarded block of the task lasting 5 min. Baseline high-resolution T1-weigthed MR images were obtained. Reaction time increased with time-on-task but got faster again in the rewarded block. Participants' subjective fatigue increased during task performance. In addition, we found that higher increase in subjective mental fatigue was associated with the cortical thickness of the following areas: bilateral precuneus, right precentral gyrus; right pars triangularis and left superior frontal gyrus. Our results suggest that individual differences in subjective mental fatigue may be explained by differences in the degree of cortical thickness of areas that are associated with motor processes, executive functions, intrinsic alertness and are parts of the default mode network.

Evaluating the effects of brain injury, disease and tasks on cognitive fatigue

Because cognitive fatigue (CF) is common and debilitating following brain injury or disease we investigated the relationships among CF, behavioral performance, and cerebral activation within and across populations by combining the data from two cross-sectional studies. Individuals with multiple sclerosis (MS) were included to model CF resulting from neurological disease; individuals who had sustained a traumatic brain injury (TBI) were included to model CF resulting from neurological insult; both groups were compared with a control group (Controls). CF was induced while neuroimaging data was acquired using two different tasks. CF significantly differed between the groups, with the clinical groups reporting more CF than Controls-a difference that was statistically significant for the TBI group and trended towards significance for the MS group. The accrual of CF did not differ across the three groups; and CF ratings were consistent across tasks. Increasing CF was associated with longer response time for all groups. The brain activation in the caudate nucleus and the thalamus was consistently correlated with CF in all three groups, while more dorsally in the caudate, activation differed across the groups. These results suggest the caudate and thalamus to be central to CF while more dorsal aspects of the caudate may be sensitive to damage associated with particular types of insult.

Development of Care Pathway for Assessment and Treatment of Fatigue in Palliative Care

Objectives

Fatigue is a frequent and burdensome symptom in patients with advanced disease in palliative care. However, it is under-assessed and undertreated in clinical practice, even though many treatment options have been identified in systematic reviews. Care pathways with defined and standardised steps have been recommended for effective management in the clinical setting. This paper describes a care pathway for managing fatigue in palliative care patients. This study aims to develop a care pathway with detailed guidance for screening, assessment, diagnosis, and treatment of fatigue in palliative care patients.

Material and methods

A collaborative effort of multidisciplinary clinicians participated in constructing the care pathway. The care pathway was developed using the following steps: (a) Developing an intervention; (b) piloting and feasibility; (c) evaluating the intervention; (d) reporting; and (e) implementation. This paper covers the first step, which includes the evidence base identification, theory identification/development, and process/outcomes modeling. A literature search was conducted to understand the extent of the fatigue problem in the palliative care setting and identify existing guidelines and strategies for managing fatigue. Consistent recommendations emanating from the included papers were then contributed to a care pathway. Patient representatives and palliative care professionals provided feedback on the draft.

Results

The care pathway address the following care processes: (1) Screening for the presence of fatigue; (2) assessment to evaluate the severity of fatigue; (3) diagnostic procedure, including history, physical examination, and laboratory finding; (4) therapeutic management pathway for clinical decision-making; and (5) valuation of treatment effect, using questionnaires, diaries and physical activity monitoring with body-worn sensors.

Conclusion

The development of a care pathway will help to implement regular and structured assessment, diagnosis, and treatment of fatigue for healthcare professionals treating palliative care patients. Reviewing the pathway with a multidisciplinary expert group and field testing the pathway will be the next steps toward implementation.

Reduced clinical connectome fingerprinting in multiple sclerosis predicts fatigue severity

BACKGROUND

Brain connectome fingerprinting is progressively gaining ground in the field of brain network analysis. It represents a valid approach in assessing the subject-specific connectivity and, according to recent studies, in predicting clinical impairment in some neurodegenerative diseases. Nevertheless, its performance, and clinical utility, in the Multiple Sclerosis (MS) field has not yet been investigated.

METHODS

We conducted the Clinical Connectome Fingerprint (CCF) analysis on source-reconstructed magnetoencephalography signals in a cohort of 50 subjects: twenty-five MS patients and twenty-five healthy controls.

RESULTS

All the parameters of identifiability, in the alpha band, were reduced in patients as compared to controls. These results implied a lower similarity between functional connectomes (FCs) of the same patient and a reduced homogeneity among FCs in the MS group. We also demonstrated that in MS patients, reduced identifiability was able to predict, fatigue level (assessed by the Fatigue Severity Scale).

CONCLUSION

These results confirm the clinical usefulness of the CCF in both identifying MS patients and predicting clinical impairment. We hope that the present study provides future prospects for treatment personalization on the basis of individual brain connectome.

Subjective valuation of performance feedback is robust to trait cognitive fatigue in multiple sclerosis

BACKGROUND

Performance feedback is vital to rehabilitation interventions that treat cognitive impairments from multiple sclerosis (MS). Optimal treatment relies on participants' motivation to learn from feedback throughout these interventions. Cognitive fatigue, a prevalent symptom of MS, is associated with aberrant reward processing, which necessitates research into how fatigue affects perceived reward value of feedback in these individuals. The current study investigated how trait fatigue influences subjective valuation of feedback and subsequent feedback-seeking behavior in people with MS.

METHODS

33 MS and 32 neurotypical (NT) participants completed a willingness-to-pay associative memory paradigm that assessed feedback valuation via trial-by-trial decisions to either purchase or forego feedback in service of maximizing a performance-contingent monetary reward. Participant ratings of trait fatigue were also collected. Generalized logistic mixed modeling was used to analyze factors that influenced trial-wise feedback purchase decisions and task performance.

RESULTS

Despite reporting greater trait fatigue, MS participants purchased comparable amounts of feedback as NT participants. Like NT participants, MS participants were more likely to purchase feedback when they were less confident about response accuracy. MS participants also performed comparably to NT participants, who both particularly benefited from purchase decisions that yielded negative feedback (i.e., indicating a response error).

CONCLUSIONS

Trait cognitive fatigue may not impact performance feedback valuation in people with MS. Nonetheless, confidence in performance may drive their feedback-seeking behavior and may serve as a target for improving learning throughout cognitive rehabilitation and maximizing treatment success.

Fatigue and Human Performance: An Updated Framework

Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.

Altered functional connectivity during performance feedback processing in multiple sclerosis

Effective learning from performance feedback is vital for adaptive behavior regulation necessary for successful cognitive performance. Yet, how this learning operates in clinical groups that experience cognitive dysfunction is not well understood. Multiple sclerosis (MS) is an autoimmune, degenerative disease of the central nervous system characterized by physical and cognitive dysfunction. A highly prevalent impairment in MS is cognitive fatigue (CF). CF is associated with altered functioning within cortico-striatal regions that also facilitate feedback-based learning in neurotypical (NT) individuals. Despite this cortico-striatal overlap, research about feedback-based learning in MS, its associated neural underpinnings, and its sensitivity to CF, are all lacking. The present study investigated feedback-based learning ability in MS, as well as associated cortico-striatal function and connectivity. MS and NT participants completed a functional magnetic resonance imaging (fMRI) paired-word association task during which they received trial-by-trial monetary, non-monetary, and uninformative performance feedback. Despite reporting greater CF throughout the task, MS participants displayed comparable task performance to NTs, suggesting preserved feedback-based learning ability in the MS group. Both groups recruited the ventral striatum (VS), caudate nucleus, and ventromedial prefrontal cortex in response to the receipt of performance feedback, suggesting that people with MS also recruit cortico-striatal regions during feedback-based learning. However, compared to NT participants, MS participants also displayed stronger functional connectivity between the VS and task-relevant regions, including the left angular gyrus and right superior temporal gyrus, in response to feedback receipt. Results indicate that CF may not interfere with feedback-based learning in MS. Nonetheless, people with MS may recruit alternative connections with the striatum to assist with this form of learning. These findings have implications for cognitive rehabilitation treatments that incorporate performance feedback to remediate cognitive dysfunction in clinical populations.

The neural correlates of mental fatigue and reward processing: A task-based fMRI study

Increasing time spent on the task (i.e., the time-on-task (ToT) effect) often results in mental fatigue. Typical effects of ToT are decreasing levels of task-related motivation and the deterioration of cognitive performance. However, a massive body of research indicates that the detrimental effects can be reversed by extrinsic motivators, for example, providing rewards to fatigued participants. Although several attempts have been made to identify brain areas involved in mental fatigue and related reward processing, the neural correlates are still less understood. In this study, we used the psychomotor vigilance task to induce mental fatigue and blood oxygen-level-dependent functional magnetic resonance imaging to investigate the neural correlates of the ToT effect and the reward effect (i.e., providing extra monetary reward after fatigue induction) in a healthy young sample. Our results were interpreted in a recently proposed neurocognitive framework. The activation of the right middle frontal gyrus, right insula and right anterior cingulate gyrus decreased as fatigue emerged and the cognitive performance dropped. However, after providing an extra reward, the cognitive performance, as well as activation of these areas, increased. Moreover, the activation levels of all of the mentioned areas were negatively associated with reaction times. Our results confirm that the middle frontal gyrus, insula and anterior cingulate cortex play crucial roles in cost-benefit evaluations, a potential background mechanism underlying fatigue, as suggested by the neurocognitive framework.

Investigating the influence of an effort-reward interaction on cognitive fatigue in individuals with multiple sclerosis

This study examined whether an alteration in the effort-reward relationship, a theoretical framework based on cognitive neuroscience, could explain cognitive fatigue. Forty persons with MS and 40 healthy age- and education-matched cognitively healthy controls (HC) participated in a computerized switching task with orthogonal high- and low-demand (effort) and reward manipulations. We used the Visual Analog Scale of Fatigue (VAS-F) to assess subjective state fatigue before and after each condition during the task. We used mixed-effects models to estimate the association and interaction between effort and reward and their relationship to subjective fatigue and task performance. We found the high-demand condition was associated with increased VAS-F scores (p < .001), longer response times (RT) (p < .001) and lower accuracy (p < .001). The high-reward condition was associated with faster RT (p = .006) and higher accuracy (p = .03). There was no interaction effect between effort and reward on VAS-F scores or performance. Participants with MS reported higher VAS-F scores (p = .02). Across all conditions, participants with MS were slower (p < .001) and slower as a function of condition demand compared with HC (p < .001). This behavioural study did not find evidence that an effort-reward interaction is associated with cognitive fatigue. However, our findings support the role of effort in subjective cognitive fatigue and both effort and reward on task performance. In future studies, more salient reward manipulations could be necessary to identify effort-reward interactions on subjective cognitive fatigue.

The effectiveness of amantadine and dalfampridine in improving fatigue in patients with multiple sclerosis: A randomized, double-blind, clinical trial

Background: Fatigue is a common complication associated with multiple sclerosis (MS). The aim of this study was to evaluate the impact of dalfampridine and amantadine on fatigue in patients with MS. Methods: This was a randomized, double-blind, clinical trial on patients with MS. The recruited patients were adults (≥ 18 years old) diagnosed with MS; their Expanded Disability Status Scale (EDSS) was between 0.0 and 5.5, and their fatigue was confirmed by the Modified Fatigue Impact Scale (MFIS). They were randomly assigned to the amantadine (100 mg twice daily) and dalfampridine (10 mg twice daily) for eight weeks. The primary outcome was the improvement of fatigue score, and the secondary outcome was assessment of quality of life by the Short-Form Health Survey (SF-36) and any reported side effects. Results: A total of 69 patients were recruited, and 54 of them were analyzed. The mean MFIS significantly improved in both groups after one and two months compared to baseline: amantadine: first month: 40.63 ± 14.35 (P = 0.040), second month: 36.56 ± 17.12 (P = 0.010); dalfampridine: first month: 38.29 ± 15.23 (P = 0.001), second month: 34.26 ± 18.30 (P = 0.001). However, the amount of changes from baseline was not significantly different (amantadine, P = 0.090; dalfampridine, P = 0.130). The amount of changes in quality of life showed no significant improvement (P = 0.210). Conclusion: The results showed that dalfampridine was not different with amantadine in improving fatigue in patients with MS; besides, it showed an acceptable safety profile. Therefore, it can be considered as a possible beneficial therapeutic agent in MS fatigue.

Interpreting the clinical importance of the relationship between subjective fatigue and cognitive impairment in multiple sclerosis (MS): How BICAMS performance is affected by MS-related fatigue

BACKGROUND

There is evidence that subjective fatigue can influence cognitive functioning in multiple sclerosis (MS). DeLuca et al.'s (2004) Relative Consequence Model proposes that impairments to other high-level cognitive functions, such as memory, result from the disease's effect on information processing speed.

OBJECTIVE

The primary aims of the study were to investigate both 1) the relationship between subjective fatigue and cognitive functioning, as measured by the widely used Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) in MS; and 2) the consequential effect of fatigue on information processing speed as predicted by the Relative Consequence Model.

METHODS

192 participants with MS attending tertiary referral MS centre completed the Modified Fatigue Impact Scale and BICAMS.

RESULTS

Multiple correlation analyses determined that there were statistically significant relationships between all domains assessed by the BICAMS and levels of fatigue, such that higher levels of self-reported fatigue were associated with lower performance on information-processing, and visual and verbal learning. After controlling for information processing speed, the strength of correlation between fatigue and learning performance weakened. Linear regression analysis showed that fatigue predicted the most variance in verbal learning and 11.7% of the overall variance in BICAMS performance.

CONCLUSION

Subjective fatigue and objective cognitive performance in MS are related. Caution is advised in the interpretation of BICAMS scores in cases where high levels of fatigue are present, and more detailed neuropsychological assessments may be required in order to accurately identify objective cognitive impairment independent of subjective fatigue.

Listening to 15 Hz Binaural Beats Enhances the Connectivity of Functional Brain Networks in the Mental Fatigue State—An EEG Study

Introduction: It is clear that mental fatigue can have many negative impacts on individuals, such as impairing cognitive function or affecting performance. The aim of this study was to investigate the role of sound interventions in combating mental fatigue. Method: The subjects were assessed on various scales, a psychomotor vigilance task (PVT) task, and a 3 min resting-state electroencephalogram (EEG), followed by a 20 min mental fatigue–inducing task (Time Load Dual Back, TloadDback), during which subjects in different condition groups listened to either 15 Hz binaural beats, 40 Hz binaural beats, relaxing music, or a 240 Hz pure tone. After the mental fatigue–inducing task, subjects were again assessed on various scales, a PVT task, and a 3 min resting-state EEG. Results: After the fatigue-inducing task, there was no significant difference between the four groups on the scales or the PVT task performance. In TloadDback, the accuracy rate of the 40 Hz binaural beats group and the relaxing music group decreased in the middle stage of the task, while the 15 Hz binaural beats group and the 240 Hz pure tone group remained unchanged in all stages of the task. The EEG results showed that after fatigue inducement, the average path length of the 15 Hz binaural beats group decreased, and local efficiency showed an increasing tendency, indicating enhanced brain network connectivity. Meanwhile, the 240 Hz pure tone group showed enhanced functional connectivity, suggesting a state of mental fatigue in the group. Conclusions: The results of this study show that listening to 15 Hz binaural beats is a proven intervention for mental fatigue that can contribute to maintaining working memory function, enhancing brain topological structure, and alleviating the decline in brain function that occurs in a mentally fatigued state. As such, these results are of great scientific and practical value.

Associations of White Matter and Basal Ganglia Microstructure to Cognitive Fatigue Rate in Multiple Sclerosis

Fatigue, including cognitive fatigue, is one of the most debilitating symptoms reported by persons with multiple sclerosis (pwMS). Cognitive fatigue has been associated with disruptions in striato-thalamo-cortical and frontal networks, but what remains unknown is how the rate at which pwMS become fatigued over time relates to microstructural properties within the brain. The current study aims to fill this gap in knowledge by investigating how cognitive fatigue rate relates to white matter and basal ganglia microstructure in a sample of 62 persons with relapsing-remitting MS. Participants rated their level of cognitive fatigue at baseline and after each block (x7) of a within-scanner cognitive fatigue inducing task. The slope of the regression line of all eight fatigue ratings was designated as “cognitive fatigue rate.” Diffusional kurtosis imaging maps were processed using tract-based spatial statistics and regional analyses (i.e., basal ganglia) and associated with cognitive fatigue rate. Results showed cognitive fatigue rate to be related to several white matter tracts, with many having been associated with basal ganglia connectivity or the previously proposed “fatigue network.” In addition, cognitive fatigue rate was associated with the microstructure within the putamen, though this did not survive multiple comparisons correction. Our approach of using cognitive fatigue rate, rather than trait fatigue, brings us closer to understanding how brain pathology may be impacting the experience of fatigue in the moment, which is crucial for developing interventions. These results hold promise for continuing to unpack the complex construct that is cognitive fatigue.

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Fatigue is one of the most common debilitating symptoms reported by persons with multiple sclerosis (MS). It reflects feelings of tiredness, lack of energy, low motivation, and difficulty in concentrating. It can be measured at a specific instant in time as a perception that arises from interoceptive networks involved in the regulation of homeostasis. Such ratings indicate the state level of fatigue and likely reflect an inability to correct deviations from a balanced homeostatic state. In contrast, the trait level of fatigue is quantified in terms of work capacity (fatigability), which can be either estimated (perceived fatigability) or measured (objective fatigability). Clinically, fatigue is most often quantified with questionnaires that require respondents to estimate their past capacity to perform several cognitive, physical, and psychosocial tasks. These retrospective estimates provide a measure of perceived fatigability. In contrast, the change in an outcome variable during the actual performance of a task provides an objective measure of fatigability. Perceived and objective fatigability do not assess the same underlying construct. Persons with MS who report elevated trait levels of fatigue exhibit deficits in interoceptive networks (insula and dorsal anterior cingulate cortex), including increased functional connectivity during challenging tasks. The state and trait levels of fatigue reported by an individual can be modulated by reward and pain pathways. Understanding the distinction between fatigue and fatigability is critical for the development of effective strategies to reduce the burden of the symptom for individuals with MS.

Increasing the Clinical Utility of the Paced Auditory Serial Addition Test: Normative Data for Standard, Dyad, and Cognitive Fatigability Scoring

BACKGROUND

No normative data currently exist that would allow clinicians to decide whether the degree of cognitive fatigability (CF) experienced in individuals with neurologic disease is greater than expected when compared with a healthy population.

OBJECTIVE

To establish discrete and regression-based normative data for CF as defined by an objective decrement in performance over the course of a cognitive task; namely, the Paced Auditory Serial Addition Test (PASAT). In addition, to develop discrete and regression-based normative data for PASAT performance scores-dyad and percent dyad-for which data do not currently exist.

METHOD

One hundred and seventy-eight healthy individuals completed the PASAT as part of a larger neuropsychological battery. PASAT performance scores including total correct responses, total dyads, and percent dyad were calculated. CF scores were calculated by comparing the individuals' performance on the first half (or third) of the test to their performance on the last half (or third) in order to capture any within-task performance decrements over time.

RESULTS

Both age- and education-based discrete normative data and demographically adjusted (sex, age, and education) regression-based formulas were established for the PASAT performance scores and the CF scores.

CONCLUSION

The development of these normative data will allow for greater interpretation of an individual's performance on the PASAT, beyond just the total correct score, through the use of dyad and percent dyad scores. With respect to CF, these data will allow clinicians to objectively quantify decrements in cognitive performance over time better in individuals with neurologic diseases.

Bored Into Depletion? Toward a Tentative Integration of Perceived Self-Control Exertion and Boredom as Guiding Signals for Goal-Directed Behavior

During the past two decades, self-control research has been dominated by the strength model of self-control, which is built on the premise that the capacity for self-control is a limited global resource that can become temporarily depleted, resulting in a state called ego depletion. The foundations of ego depletion have recently been questioned. Thus, although self-control is among the most researched psychological concepts with high societal relevance, an inconsistent body of literature limits our understanding of how self-control operates. Here, we propose that the inconsistencies are partly due to a confound that has unknowingly and systematically been introduced into the ego-depletion research: boredom. We propose that boredom might affect results of self-control research by placing an unwanted demand on self-control and signaling that one should explore behavioral alternatives. To account for boredom in self-controlled behavior, we provide a working model that integrates evidence from reward-based models of self-control and recent theorizing on boredom to explain the effects of both self-control exertion and boredom on subsequent self-control performance. We propose that task-induced boredom should be systematically monitored in self-control research to assess the validity of the ego-depletion effect.

Rapid, precise, and reliable measurement of delay discounting using a Bayesian learning algorithm

Machine learning has the potential to facilitate the development of computational methods that improve the measurement of cognitive and mental functioning. In three populations (college students, patients with a substance use disorder, and Amazon Mechanical Turk workers), we evaluated one such method, Bayesian adaptive design optimization (ADO), in the area of delay discounting by comparing its test-retest reliability, precision, and efficiency with that of a conventional staircase method. In all three populations tested, the results showed that ADO led to 0.95 or higher test-retest reliability of the discounting rate within 10-20 trials (under 1-2 min of testing), captured approximately 10% more variance in test-retest reliability, was 3-5 times more precise, and was 3-8 times more efficient than the staircase method. The ADO methodology provides efficient and precise protocols for measuring individual differences in delay discounting.

Cognitive Fatigability is Independent of Subjective Cognitive Fatigue and Mood in Multiple Sclerosis

BACKGROUND

Sustained cognitive testing is used to detect cognitive fatigability and is often considered a substitute for subjective cognitive fatigue (CF). However, the relationship between cognitive fatigability and subjective CF in people with multiple sclerosis (PwMS) remains undetermined.

OBJECTIVE

To explore potential associations between fatigability induced by sustained cognitive testing and subjective CF in PwMS.

METHODS

We gave 120 PwMS and 60 demographically matched, healthy individuals the Beck Depression Inventory-FastScreen (BDI-FS) to measure mood and the Modified Fatigue Impact Scale to measure CF. In addition, we used the Quotient ADHD Test, a sustained attention test, to measure cognitive fatigability. We also explored potential correlations between the individuals' performance on the sustained attention test and thalamic volume using recent MRI scans.

RESULTS

Forty-one (34.2%) of the PwMS exhibited cognitive fatigability. These 41 were found to be significantly older (P=0.006), had been diagnosed with the disease for longer (P=0.03), had higher scores (P<0.001) on the Expanded Disability Status Scale, and had reduced thalamic volume (P=0.04) compared with the 79 (65.8%) PwMS not exhibiting cognitive fatigability. The PwMS exhibiting cognitive fatigability scored similarly on the BDI-FS (P=0.21) and self-reported similar rates of CF (P=0.62) as the PwMS not exhibiting cognitive fatigability.

CONCLUSION

Cognitive fatigability induced by sustained cognitive testing is not an accurate clinical alternative to subjective CF. This study provides evidence to support cognitive fatigability and CF in PwMS as two distinct concepts.

Neural mechanisms underlying state mental fatigue in multiple sclerosis: a pilot study

Neuroimaging underpinnings of state (in the moment, transient) mental fatigue in multiple sclerosis (MS) are not well understood. The current pilot study examined the effect of state mental fatigue on brain activation (measured using functional magnetic resonance imaging [fMRI]) during conditions of varying cognitive loads of rapid information processing in persons with MS relative to healthy controls. Nineteen persons with MS and 17 healthy controls underwent fMRI scanning while performing a modified version of the Symbol Digit Modalities Test, which consisted of high and low cognitive load conditions with comparable visual stimulation. State mental fatigue was assessed using the Visual Analog Scale of Fatigue before and after each run of the behavioral task. Results indicated that the healthy control group recruited significantly more anterior brain regions (superior and middle frontal gyri, insula, and superior temporal gyrus) to meet increased task demands during the high cognitive load condition as fatigue level increased (p < 0.05), which was accompanied by shorter response time. In contrast, the MS group did not recruit anterior areas to the same extent as the healthy control group as task demands and fatigue increased. Indeed, the MS group continued to activate more posterior brain regions (precuneus, lingual gyrus, and middle occipital gyrus) for the high cognitive load condition (p < 0.05) with no improvement in speed. In conclusion, persons with MS may allocate neural resources less efficiently than healthy controls when faced with increased task demands, which may result in increased mental fatigue. Results of the current pilot investigation warrant replication with a larger sample size.

Cognitive fatigability is a quantifiable distinct phenomenon in multiple sclerosis

Cognitive fatigability in multiple sclerosis represents the decrease in cognitive performance over time. It is a frequent symptom that negatively affects quality of life and ability to work. There are no objective measures of cognitive fatigability. This study aimed at quantifying cognitive fatigability despite the learning effect and to clarify whether cognitive fatigability represents a free-standing phenomenon rather than an aspect of cognitive impairment. We measured information processing speed with the Symbol Digit Modalities Test, and the number of right answers was recorded every 30 s for 180 s. We approximated the number of right answers as function of time with two logarithmic models, one including a first-order term alone and the other adding also a second-order term. The coefficient of the latter (B) may quantify performance deflection and may represent cognitive fatigability. We tested 173 patients with multiple sclerosis, including 119 cognitively impaired and 54 cognitively preserved patients, and 35 healthy subjects. The performance of cognitively preserved patients showed a deflection at the end of task that was detected neither in controls nor in cognitively impaired patients and needed a second-order term to be approximated (p < .03, F = 14.02). B was explained neither by depression nor fatigue. We proposed for the first time a method to quantify cognitive fatigue via a second-order least square fit model, easily usable in the clinical practice. By using this novel approach, cognitive fatigability results to be a free-standing phenomenon that is more evident in cognitively preserved than in cognitive impaired patients.

Task duration and task order do not matter: no effect on self-control performance

The strength model of self-control proposes that all acts of self-control are energized by one global limited resource that becomes temporarily depleted by a primary self-control task, leading to impaired self-control performance in secondary self-control tasks. However, failed replications have cast doubt on the existence of this so-called ego depletion effect. Here, we investigated between-task (i.e., variation in self-control tasks) and within-task variation (i.e., task duration) as possible explanations for the conflicting literature on ego depletion effects. In a high-powered experiment (N = 709 participants), we used two established self-control tasks (Stroop task, transcription task) to test how variations in the duration of primary and secondary self-control tasks (2, 4, 8, or 16 min per task) affect the occurrence of an ego depletion effect (i.e., impaired performance in the secondary task). In line with the ego depletion hypothesis, subjects perceived longer lasting secondary tasks as more self-control demanding. Contrary to the ego depletion hypothesis, however, performance did neither suffer from prior self-control exertion, nor as a function of task duration. If anything, performance tended to improve when the primary self-control task lasted longer. These effects did not differ between the two self-control tasks, suggesting that the observed null findings were independent of task type.

Mental Fatigue Increases Gait Variability During Dual-task Walking in Old Adults

Background

Mental fatigue is a psychobiological state induced by sustained periods of demanding cognitive activity and is characterized by feelings of tiredness which are common in everyday life. Recently, it has been hypothesized that mental fatigue might have an impact on gait performance in old adults. Therefore, the effect of mental fatigue on gait performance under single- and dual-task conditions was investigated in young and old participants.

Methods

Spatio-temporal gait parameters of 16 young and 16 old healthy participants were measured using a photoelectric system during single- and dual-task walking before and after a randomly assigned mental fatigue (performing a stop-signal task for 90 minutes) and control intervention (watching a video for 90 minutes), respectively. Changes in subjective fatigue, wakefulness, mood, arousal, and psychophysiological workload (heart rate variability indices) were assessed.

Results

Psychometric measures indicated increased subjective fatigue and arousal as well as decreased mood and wakefulness after the mental fatigue task. Heart rate variability indices revealed a higher psychophysiological workload during the mental fatigue intervention in old compared to young participants. Gait measures (coefficient of variation of speed, stride length, and stance time) revealed impaired dual-task walking performance following the mental fatigue intervention only in old participants.

Conclusion

Data indicate that mental fatigue, induced by sustained cognitive activity, can impair gait performance during dual-task walking in old adults. The susceptibility to mental fatigue could be a new intrinsic risk factor for falls in older people and should be taken into account when dual-task gait analyses are performed.

Cognitive Fatigue in Multiple Sclerosis: An Objective Approach to Diagnosis and Treatment by Transcranial Electrical Stimulation

Cognitive fatigue is one of the most frequent symptoms in multiple sclerosis (MS), associated with significant impairment in daily functioning and quality of life. Despite its clinical significance, progress in understanding and treating fatigue is still limited. This limitation is already caused by an inconsistent and heterogeneous terminology and assessment of fatigue. In this review, we integrate previous literature on fatigue and propose a unified schema aiming to clarify the fatigue taxonomy. With special focus on cognitive fatigue, we survey the significance of objective behavioral and electrophysiological fatigue parameters and discuss the controversial literature on the relationship between subjective and objective fatigue assessment. As MS-related cognitive fatigue drastically affects quality of life, the development of efficient therapeutic approaches for overcoming cognitive fatigue is of high clinical relevance. In this regard, the reliable and valid assessment of the individual fatigue level by objective parameters is essential for systematic treatment evaluation and optimization. Transcranial electrical stimulation (tES) may offer a unique opportunity to manipulate maladaptive neural activity underlying MS fatigue. Therefore, we discuss evidence for the therapeutic potential of tES on cognitive fatigue in people with MS.

Attention Measures of Accuracy, Variability, and Fatigue Detect Early Response to Donepezil in Alzheimer's Disease: A Randomized, Double-blind, Placebo-Controlled Pilot Trial

OBJECTIVE

Donepezil is widely used to treat Alzheimer's disease (AD), but detecting early response remains challenging for clinicians. Acetylcholine is known to directly modulate attention, particularly under high cognitive conditions, but no studies to date test whether measures of attention under high load can detect early effects of donepezil. We hypothesized that load-dependent attention tasks are sensitive to short-term treatment effects of donepezil, while global and other domain-specific cognitive measures are not.

METHOD

This longitudinal, randomized, double-blind, placebo-controlled pilot trial (ClinicalTrials.gov Identifier: NCT03073876) evaluated 23 participants newly diagnosed with AD initiating de novo donepezil treatment (5 mg). After baseline assessment, participants were randomized into Drug (n = 12) or Placebo (n = 11) groups, and retested after approximately 6 weeks. Cognitive assessment included: (a) attention tasks (Foreperiod Effect, Attentional Blink, and Covert Orienting tasks) measuring processing speed, top-down accuracy, orienting, intra-individual variability, and fatigue; (b) global measures (Alzheimer's Disease Assessment Scale-Cognitive Subscale, Mini-Mental Status Examination, Dementia Rating Scale); and (c) domain-specific measures (memory, language, visuospatial, and executive function).

RESULTS

The Drug but not the Placebo group showed benefits of treatment at high-load measures by preserving top-down accuracy, improving intra-individual variability, and averting fatigue. In contrast, other global or cognitive domain-specific measures could not detect treatment effects over the same treatment interval.

CONCLUSIONS

The pilot-study suggests that attention measures targeting accuracy, variability, and fatigue under high-load conditions could be sensitive to short-term cholinergic treatment. Given the central role of acetylcholine in attentional function, load-dependent attentional measures may be valuable cognitive markers of early treatment response.

Uncovering the association between fatigue and fatigability in multiple sclerosis using cognitive control

BACKGROUND

Fatigue and cognitive dysfunction are two common symptoms experienced by patients with multiple sclerosis (MS). The relationship between subjective and objective fatigue (fatigability) in MS is poorly understood. Cognitive control tasks might be more conducive to fatigability and more likely to show associations between subjective and objective cognitive fatigue in MS.

OBJECTIVE

To study the association between objective fatigability, as induced by a cognitive control task called the Blocked Cyclic Naming Task (BCNT), subjective fatigue and baseline cognitive functioning in patients with MS.

METHODS

Twenty-one patients with MS completed baseline questions about their disease, the Montreal Cognitive Assessment (MoCA) battery and self-reported questionnaires on trait fatigue, sleep and depression. Disability was captured using the expanded disability status scale (EDSS). Participants then performed the BCNT and were asked about their level of state momentary fatigue before and after the BCNT. The BCNT consists of several blocks of either related or unrelated pictures that participants name as quickly as possible. The pictures cycled 4 times in each block and the difference in the response times (RTs) between related and unrelated blocks was captured. Data were analyzed using repeated measures analysis of variance and Pearson correlations.

RESULTS

MS participants' performance declined for the related, but not unrelated blocks. The difference in RTs between related and unrelated conditions increased with repetition across cycles (p < 0.001). Participants also showed objective fatigability with less repetition priming (p = 0.02) in the 4th quarter and with greater differences between related and unrelated conditions in the later part of the task. Objective fatigability was strongly associated with participants' assessment of their level of momentary state fatigue (r = 0.612, p = 0.007).

CONCLUSION

Using the appropriate tools, this study showed an association between subjective and objective cognitive fatigue in people with MS. The BCNT and cognitive control are useful tools in assessing patients with MS and should be explored in future, larger studies in this population.

Task-Based Cognitive Fatigability for Older Adults and Validation of Mental Fatigability Subscore of Pittsburgh Fatigability Scale

Cognitive fatigue and cognitive fatigability are distinct constructs. Cognitive fatigue reflects perception of cognitive fatigue outside of the context of activity level and duration and can be reliably assessed via established instruments such as the Fatigue Severity Scale (FSS) and the Modified Fatigue Impact Scale (MFIS). In contrast, cognitive fatigability reflects change in fatigue levels quantified within the context of the level and duration of cognitive activity, and currently there are no reliable measures of cognitive fatigability. A recently published scale, the Pittsburgh Fatigability Scale (PFS), attempts to remedy this problem with a focus on the aged population. While the physical fatigability subscore of PFS has been validated using physical activity derived measures, the mental fatigability subscore of PFS remains to be tested against equivalent measures derived from cognitive activities. To this end, we recruited 35 older, healthy adult participants (mean age 73.77 ± 5.9) to complete the PFS as well as a prolonged continuous performance of a Stroop task (>2 h). Task-based assessments included time-on-task changes in self-reported fatigue scores (every 20 min), reaction time, and pupil diameter. Defining subjective fatigability, behavioral fatigability, and physiologic/autonomic fatigability to be the slope of change over time-on-task in the above three assessed variables, we found that the PFS mental subscore was not correlated with any of the three task-based fatigability measures. Instead, the PFS mental subscore was correlated with trait level fatigue measures FSS (ρ = 0.63, p < 0.001), and MFIS cognitive subsection (ρ = 0.36, p = 0.03). This finding suggested that the PFS mental fatigability subscore may not be an adequate measure of how fatigued one becomes after a given amount of mental work. Further development efforts are needed to create a self-report scale that reliably captures cognitive fatigability in older adults.

Cognitive Fatigue, Sleep and Cortical Activity in Multiple Sclerosis Disease. A Behavioral, Polysomnographic and Functional Near-Infrared Spectroscopy Investigation

Patients with multiple sclerosis (MS) disease frequently experience fatigue as their most debilitating symptom. Fatigue in MS partially refers to a cognitive component, cognitive fatigue (CF), characterized by a faster and stronger than usual development of the subjective feeling of exhaustion that follows sustained cognitive demands. The feeling of CF might result from supplementary task-related brain activity following MS-related demyelination and neurodegeneration. Besides, CF in MS disease might also stem from disrupted sleep. The present study investigated the association between the triggering of CF, task-related brain activity and sleep features. In a counterbalance mixed design, 10 patients with MS and 11 healthy controls were exposed twice for 16 min to a CF-inducing dual working memory updating task (TloadDback) under low or high cognitive demands conditions, counterbalanced. Considering known inter-individual differences and potential cognitive deficits in MS, the maximal cognitive load of the task was individually adapted to each participant’s own upper limits. During the experimental sessions, cortical brain activity was measured using near-infrared spectroscopy (NIRS) during the CF-induction task, and in a resting state immediately before and after. Ambulatory polysomnography recordings were obtained on the nights preceding experimental sessions. When cognitive load was individually adapted to their processing capabilities, patients with MS exhibited similar than healthy controls levels of subjectively perceived CF, evolution of performance during the task, and brain activity patterns. Linear mixed models indicate a negative association between oxygenation level changes in the dorsolateral prefrontal cortex (DLPFC) and the triggering of subjective CF in patients with MS only. Longer total sleep time was also associated with higher CF in MS patients. These results suggest that controlling for cognitive load between individuals with and without MS results in a similar task-related development of subjective CF. Besides comparable performance and cortical brain activity between groups, mixed model analyses suggest a possible association between CF, DLPFC activity and sleep duration in MS disease.

The impact of text segmentation on subtitle reading

Understanding the way people watch subtitled films has become a central concern for subtitling researchers in recent years. Both subtitling scholars and professionals generally believe that in order to reduce cognitive load and enhance readability, line breaks in twoline subtitles should follow syntactic units. However, previous research has been inconclusive as to whether syntactic-based segmentation facilitates comprehension and reduces cognitive load. In this study, we assessed the impact of text segmentation on subtitle processing among different groups of viewers: hearing people with different mother tongues (English, Polish, and Spanish) and deaf, hard of hearing, and hearing people with English as a first language. We measured three indicators of cognitive load (difficulty, effort, and frustration) as well as comprehension and eye tracking variables. Participants watched two video excerpts with syntactically and non-syntactically segmented subtitles. The aim was to determine whether syntactic-based text segmentation as well as the viewers’ linguistic background influence subtitle processing. Our findings show that non-syntactically segmented subtitles induced higher cognitive load, but they did not adversely affect comprehension. The results are discussed in the context of cognitive load, audiovisual translation, and deafness.

A Longitudinal Evaluation of Cognitive Fatigue on a Task of Sustained Attention in Early Relapsing-Remitting Multiple Sclerosis

Background

Cognitive fatigue can be objectively measured on tasks of sustained attention and can be defined as decreased performance as a result of sustained cognitive effort. Individuals with multiple sclerosis (MS) early in their disease are vulnerable to cognitive fatigue, although this has yet to be evaluated longitudinally. We aimed to evaluate cognitive fatigue over a 3-year interval in individuals with early-phase relapsing-remitting MS (RRMS). The sensitivity of the Paced Auditory Serial Addition Test (PASAT) at detecting cognitive fatigue was evaluated, as was the impact of scoring method.

Methods

32 people with MS and 32 controls completed the 3- and 2-second PASAT (PASAT-3″ and -2″) as a measure of sustained attention at baseline and 3-year follow-up.

Results

Performance on the PASAT remained stable across time, with improvement noted on the PASAT-2″ likely due to practice and the small sample size. Cognitive fatigue was noted at both times, although sensitivity varied based on scoring method. No evidence of worsening cognitive fatigue was noted over time. The MS group performed worse only when cognitive fatigue was the outcome variable.

Conclusions

Although individuals with MS continue to be vulnerable to cognitive fatigue at follow-up, severity does not seem to increase with time. Cognitive fatigue may be a more sensitive marker of cognitive impairment than overall task performance in those with early-phase RRMS, which has important implications given that clinically only task performance is typically assessed.

Cognitive fatigue in individuals with traumatic brain injury is associated with caudate activation

We investigated differences in brain activation associated with cognitive fatigue between persons with traumatic brain injury (TBI) and healthy controls (HCs). Twenty-two participants with moderate-severe TBI and 20 HCs performed four blocks of a difficult working memory task and four blocks of a control task during fMRI imaging. Cognitive fatigue, assessed before and after each block, was used as a covariate to assess fatigue-related brain activation. The TBI group reported more fatigue than the HCs, though their performance was comparable. Regarding brain activation, the TBI group showed a Task X Fatigue interaction in the caudate tail resulting from a positive correlation between fatigue and brain activation for the difficult task and a negative relationship for the control task. The HC group showed the same Task X Fatigue interaction in the caudate head. Because we had prior hypotheses about the caudate, we performed a confirmatory analysis of a separate dataset in which the same subjects performed a processing speed task. A relationship between Fatigue and brain activation was evident in the caudate for this task as well. These results underscore the importance of the caudate nucleus in relation to cognitive fatigue.

Calibrated imaging reveals altered grey matter metabolism related to white matter microstructure and symptom severity in multiple sclerosis

Multiple sclerosis (MS) involves damage to white matter microstructures. This damage has been related to grey matter function as measured by standard, physiologically-nonspecific neuroimaging indices (i.e., blood-oxygen-level dependent signal [BOLD]). Here, we used calibrated functional magnetic resonance imaging and diffusion tensor imaging to examine the extent to which specific, evoked grey matter physiological processes were associated with white matter diffusion in MS. Evoked changes in BOLD, cerebral blood flow (CBF), and oxygen metabolism (CMRO₂ ) were measured in visual cortex. Individual differences in the diffusion tensor measure, radial diffusivity, within occipital tracts were strongly associated with MS patients' BOLD and CMRO₂ . However, these relationships were in opposite directions, complicating the interpretation of the relationship between BOLD and white matter microstructural damage in MS. CMRO₂ was strongly associated with individual differences in patients' fatigue and neurological disability, suggesting that alterations to evoked oxygen metabolic processes may be taken as a marker for primary symptoms of MS. This work demonstrates the first application of calibrated and diffusion imaging together and details the first application of calibrated functional MRI in a neurological population. Results lend support for neuroenergetic hypotheses of MS pathophysiology and provide an initial demonstration of the utility of evoked oxygen metabolism signals for neurology research. Hum Brain Mapp 38:5375-5390, 2017. © 2017 Wiley Periodicals, Inc.

Fronto-striatal network activation leads to less fatigue in multiple sclerosis

BACKGROUND

The fronto-striatal network has been implicated in both fatigue, a common multiple sclerosis (MS) symptom, and goal attainment, which has been shown to reduce fatigue in healthy individuals.

OBJECTIVES

To investigate whether stimulation of the fronto-striatal network through goal attainment (potential monetary gain) leads to fatigue reduction in MS and healthy control (HC) participants.

METHODS

In all, 14 healthy and 19 MS participants performed a gambling task during functional magnetic resonance imaging (fMRI). Participants were presented with an opportunity to receive monetary reward during the outcome condition of the task but not during the no outcome condition. Self-reported fatigue measures were obtained after each condition and outside of the scanner. Structural alterations were also examined.

RESULTS

A significant decrease in fatigue was observed after the outcome condition compared to the no outcome condition in both groups. Significantly greater activation was observed in the ventral striatum in association with the outcome condition compared to the no outcome condition in both groups. Ventromedial prefrontal cortex showed significantly greater activation during the no outcome condition compared to the outcome condition with greater difference between conditions in the HC group.

CONCLUSION

This is the first functional neuroimaging study showing that stimulation of the fronto-striatal network through goal attainment leads to decreased on-task fatigue in MS and healthy participants.

How people with multiple sclerosis cope with a sustained finger motor task: A behavioural and fMRI study

Motor and non-motor basal ganglia (BG) circuits can help healthy subjects cope with task-induced central fatigue and re-establish motor performance after deterioration. This work aimed to assess whether patients with multiple sclerosis (MS) were able to recover motor performance after deterioration due to a demanding task and whether BG activity played a role in performance recovery in this population. Fourteen patients with MS performed a finger-tapping sequence with their right hand during three fMRI sessions: at baseline, after a demanding finger motor task (5-min sequence repetition) and after a short rest period. We observed deterioration of spatial and temporal accuracy with task repetition, as expected; after rest, temporal but not spatial accuracy recovered. Further, higher subjective fatigue was associated with increased motor performance deterioration and reduced temporal accuracy recovery. The amplitude of the BOLD signal change in the left caudate, putamen, globus pallidus, thalamus and amygdala was high at baseline and significantly reduced after the demanding task. Following rest, activity achieved values similar to the baseline in all these regions except for the amygdala. These findings suggest that patients were in a fatigue-like state since task beginning, as they showed enhanced BOLD signal change in the subcortical structures known to be recruited in healthy subjects only when coping with fatigue to recover motor performance. Abnormalities in motor and non-motor BG functions can contribute to fatigue in MS.

Operationalising cognitive fatigability in multiple sclerosis: A Gordian knot that can be cut?

BACKGROUND

Researchers have attempted to operationalise objective measures of cognitive fatigability in multiple sclerosis (MS) to overcome the perceived subjectivity of patient-reported outcomes of fatigue (PROs). Measures of cognitive fatigability examine decrements in performance during sustained neurocognitive tasks.

OBJECTIVE

This personal viewpoint briefly summarises available evidence for measures of cognitive fatigability in MS and considers their overall utility.

RESULTS

Studies suggest there may be a construct that is distinct from self-reported fatigue, reflecting a new potential intervention target. However, assessments vary and findings across and within measures are inconsistent. Few measures have been guided by a coherent theory, and those identified are likely to be influenced by other confounds, such as cognitive impairment caused more directly by disease processes, depression and assessment biases.

CONCLUSION

Future research may benefit from (a) developing a guiding theory of cognitive fatigability, (b) examining ecological and construct validity of existing assessments and (c) exploring whether the more promising cognitive fatigability measures are correlated with impaired functioning after accounting for possible confounds. Given the issues raised, we caution that our purposes as researchers may be better served by continuing our search for a more objective cognitive fatigability construct that runs in parallel with improving, rather than devaluing, current PROs.

Effects of Energy Conservation Strategies on Cancer Related Fatigue and Health Promotion Lifestyle in Breast CancerSurvivors: a Randomized Control Trial

Purpose:

Cancer-related fatigue is frequently experienced by patients during and after therapy. The present study was conducted to assess the impact of energy conservation strategies and health promotion in breast cancer survivors.

Methods:

A randomized controlled trial was carried out to compare the intervention effect (n=69.0) with controls (n=66.0) based on routine oncology ward care. The intervention was five weekly sessions for groups of 6-8 breast cancer survivors. Data on fatigue and health promotion lifestyle were obtained before and after completion the intervention and then 8 weeks later for analysis of variance (ANOVA) with repeated measures.

Results:

Our findings showed cancer-related fatigue to be reduced in the intervention group from pre- to post-intervention, and this persisted over the 8-weeks follow-up period (F = 69.8, p<0.001). All subscales of the cancer fatigue scale demonstrated statistically significant effects with partial eta-squared values ranging from 0.15 (the smallest effect in cognitive fatigue) to 0.21 (the largest for affective fatigue). Changes in the health promotion life style indicated a significant promotion from pre- to post-intervention, and this again continued after 8-weeks follow-up (F = 41.6, p < 0.001). All six domains of a health promoting life style featured significantly elevated values, the largest effect being seen in the interpersonal relations subscale (F=57.7, partial η²=0.21, p<0.001) followed by physical activity (F=51.9, partial η²=0.18, p<0.001).

Conclusions:

The program was effective in decreasing cancer related fatigue and promoting a healthy lifestyle.

On the relationship between subjective and objective measures of fatigue

OBJECTIVE

Objective and subjective methods have been used in the past to assess workplace fatigue, but little is known about correlations between them. We examine correlations between subjective and objective measures, including measures collected in a workplace scenario.

METHODS

15 young and 17 older participants were assessed before and after work with four types of fatigue measure: objective physical (posturography), objective mental (psychomotor vigilance task), subjective physical and mental (self-assessment), objective and subjective realistic (oculomotor behaviour, observer-rated facial expression, typing performance).

RESULTS

Pre- and post-test scores were analysed with an ANOVA, significant differences were submitted to a factor analysis. It yielded three factors: one representing posturography, the second self-rated mental and physical fatigue and the third observer-rated facial expression.

CONCLUSIONS

Results advocate the existence of three independent fatigue components: Objective physical fatigue, introspective and extrospective fatigue. Practitioner Summary: This study analyses correlations between different subjective and objective fatigue markers to better understand the complex nature of workplace fatigue. Measurements were conducted directly at the workplace. Results reveal that fatigue comprises three independent fatigue components: Objective physical fatigue, introspective and extrospective fatigue.

What you get from what you see: Parametric assessment of visual processing capacity in multiple sclerosis and its relation to cognitive fatigue

Multiple sclerosis (MS(1)) is a diffusely disseminated inflammatory disease affecting widespread cerebral networks. Major cognitive impairments are a reduction of processing capacity and mental fatigue, i.e., an "abnormal sense of tiredness or lack of energy". Here, the present study provides the first assessment of the distinct components of visual processing capacity based on a 'theory of visual attention' (TVA(2)) in MS patients and relates it to measures of subjective as well as (more) objective fatigue. The performance of 36 relapsing-remitting MS patients in a whole report task of brief letter arrays was compared to healthy control subjects matched for gender, age and education. Additionally, the sustained attention test PASAT-3(3) served as a measure of objective fatigue, and the self-report questionnaire MFIS(4) as a measure of subjective fatigue. Results indicate generally diminished processing speed as well as iconic memory buffers, and increased perceptual thresholds in MS patients compared to healthy controls. Block-wise analysis of attentional parameters shows that the processing speed performance of MS patients declines in the second half of the TVA-based test compared to healthy controls and in particular for patients with high versus low objective fatigue. These findings describe which aspects of processing capacity are impaired in MS, and show that fatigue mainly affects speed of processing. Thus, TVA-based assessment provides a novel approach in the determination of cognitive impairments and fatigue in MS. However, further research is required to elucidate the complex relations of processing capacity and cognitive functions in MS.