IMG01
Exploring Cognitive Effort and Associated Neural Mechanisms in MS
The high prevalence of cognitive fatigue in multiple sclerosis (MS) and its significant negative impact highlights the need for an increased understanding of factors that can lead to its reduction as well as the identification of the neural mechanism(s) underlying its reduction. Research by the current PI has successfully identified presentation of rewarding outcomes during goal-attainment as one factor that leads to cognitive fatigue reduction. However, in daily life there are multiple factors at play, the interaction of which influences behavior and symptom expression. For example, rehabilitation requires hours of effortful work from individuals and seeing value in such work is important for achieving rehabilitation gains. Given that cognitive fatigue is pervasive in individuals with MS, it is important to investigate the impact of effort on levels of fatigue and rewarding outcomes.
Objectives:
The current study examines the effect of effort on cognitive fatigue during goal-attainment in MS, as well as its associated neural mechanisms.
Methods:
Participants were told that they will undergo fMRI while engaging in a trial-and-error learning task in which they had to learn to associate abstract images with specific responses based on the outcome presented after each trial. We obtained pilot data from 9 participants with MS who scored high on the Fatigue Severity Scale (FSS; score at/above 36, indicative of high fatigue) and 5 healthy controls (HC) (FSS <36).
Results:
Accuracy was higher (better learning) in the Low Effort compared to the High Effort condition. On the post-task questionnaire, all participants indicated that the High Effort condition was indeed more difficult. The difference in fatigue levels as measured with Visual Analogue Scale between the High and Low Effort conditions are substantially more pronounced in the MS group than the HC group. On the post-task questionnaire, all participants indicated that the High Effort condition was more fatiguing but that it was also rewarding once they figured it out. Further, fMRI data from a subsample of 5 MS participants indicated higher activation during the High vs. Low Effort condition.
Conclusions:
While confirming that more effort is associated with more fatigue in both MS and HC, the current data also suggests that the neural response to outcomes associated with high effort are more rewarding, suggesting that high fatigue during effortful tasks might not be as detrimental. Examination of the effects of effort on cognitive fatigue and associated neural mechanisms will shed new light on mechanisms associated with cognitive fatigue reduction and open an avenue for more detailed investigation of treatments aimed at cognitive fatigue reduction. Such information is certainly important for practitioners to know and for individuals with MS to be aware of as it can inform treatment approaches and activities that persons with MS choose to engage in for the management of their fatigue.