Bioengineering Seminar Series - Dr. Vikram Chib

Dr. Vikram Chib will present "Fatigue and the State-Dependent Valuation of Effort in Health and Disease." Abstract Our decisions about whether to act depend not only on the costs and rewards of actions in our external environment, but also on our internal state. Physical fatigue provides a powerful example: the same action can feel easy when rested but prohibitively costly when fatigued, even though its objective requirements are unchanged. In this talk, I will present a framework for understanding fatigue as an internal state that reshapes the subjective valuation of physical effort and, consequently, decisions about whether to act. Using behavioral experiments, computational modeling, and neuroimaging, I will show that changes in neuromuscular state systematically increase the subjective cost of effort, biasing individuals away from exertion. I will present evidence that a distributed neural network, including the prefrontal and insular cortices, integrates information about the body's state into the valuation of effortful actions. I will then describe how we are extending this framework to long COVID, a condition in which persistent fatigue is among the most debilitating symptoms. Individuals with long COVID exhibit heightened sensitivity to effort costs, providing a potential mechanism linking persistent fatigue to reduced engagement in everyday activities. Together, these findings position fatigue not simply as a limitation on what the body can do, but as an internal state that shapes what the brain decides is worth doing.