Influence of Amateur Combat Sports Experience on Reinforcement Learning

Growing evidence suggests that repetitive head injury (RHI) associated with combat sports such as boxing and mixed martial arts can lead to long-term deterioration in cognitive function, including impairments in mood regulation, memory, and executive function. These changes are correlated with atrophy in brain regions including the striatum, a structure involved in goal-directed learning and action. However, although most studies have focused on professional fighters with extensive RHI, recent research suggests that even mild traumatic brain injury can produce subtle but significant impairments in specific cognitive functions. Here we propose an experiment to examine whether RHI produces selective deficits in cognitive function even at the amateur level. Specifically, given the role of the striatum in reinforcement learning, we will examine learning from positive feedback or negative feedback to choose or avoid an option, respectively. Positive and negative feedback are thought to promote learning via distinct systems, the so-called direct (“Go”) and indirect (“NoGo”) pathways, which may be differentially affected by RHI. In particular, previous research suggests that traumatic brain injury decreases neurotransmission of the D2 receptor associated with the NoGo pathway. For our experiment, we will recruit amateur fighters from the local community, along with age-, gender- and education-matched controls without a history of RHI. We hypothesize that learning from negative feedback will be impaired in amateur fighters relative to controls, controlling for individual variation in executive function and depressive symptoms. These results would further our understanding of the long-term effects of RHI on cognitive function, while identifying a specific system that may be affected by even mild trauma to the brain