Pattern Separation and Related Cognitive Functions in Combat and Contact Sports Athletes: Working Memory, Attention, and Processing Speed

Repetitive head impacts (RHIs) in combat and contact sports are associated with long-term neuropsychological consequences. The present study explores episodic memory performance, with a focus on pattern separation, a memory process associated with hippocampal function, in athletes characterized by different exposure profiles to RHIs. The study included 26 fighters (boxing, Mixed Martial Arts, Muay Thai), 20 rugby players, and 26 age-matched controls. Participants completed the Mnemonic Similarity Task (MST) and additional cognitive measures (Digit Span, Digit Symbol Substitution Test, Attentional Matrices, and N-back tasks). Group differences were assessed using ANCOVAs. Results indicated that fighters exhibited significantly poorer pattern separation performance compared to both rugby players and controls. Rugby players also performed worse than controls on the pattern separation measure, revealing a graded pattern of performance across groups. Additionally, fighters demonstrated slower reaction times during the MST and lower performance on the N-back tasks relative to both comparison groups. Overall, athletes participating in sports characterized by different exposure profiles to RHIs showed distinct patterns of cognitive performance, with the most pronounced differences observed in fighters. These findings highlight pattern separation as a potentially sensitive cognitive marker in athletes participating in combat and contact sports and underscore the need for longitudinal studies incorporating objective measures of head-impact exposure.