Effects of chemotherapy on cognitive and physical effort-based decision-making tasks in rats

Cancer-related fatigue is one of the most reported issues following cancer and its treatment, affecting the quality of life of cancer patients and survivors. However, the effects of chemotherapy on motivational and decision-making processes related to fatigue remain unclear.

This study aimed to examine the effects of the chemotherapeutic agent doxorubicin (DOX) on physical and cognitive effort-based decision-making using novel behavioural procedures in rats.

Female Sprague-Dawley rats received DOX (2 mg/kg, i.p.) or vehicle once weekly for four weeks. Voluntary wheel running was used to assess general physical activity. Physical effort-based decision-making was assessed with a T-maze concurrent choice paradigm, in which rats chose between climbing a 30-cm barrier for a high reward (HR) or entering a barrier-free arm for a low reward. Cognitive effort-based decision-making was assessed using a choice task involving lever pressing under differential reinforcement of low-rate schedules requiring different levels of response inhibition.

DOX transiently reduced voluntary activity but did not impair either physical or cognitive effort expenditure. In the T-maze, DOX-treated rats showed greater perseveration than vehicle-treated rats by continuing to choose the HR arm even after reward reduction. In the cognitive effort task, DOX-treated rats similarly perseverated by continuing to choose the HR lever despite increased inhibition demands.

These findings suggest that while DOX did not directly impair effort-based decision-making, it may disrupt executive function processes, particularly behavioural flexibility and working memory, which are critical for adapting behaviour to changing task contingencies and translating effort costs into goal-directed behaviour.