Functional Connectivity Changes in Retired Rugby League Players: A Data-Driven, Functional Magnetic Resonance Imaging Study.

There is considerable interest in the long-term brain health of retired contact and collision sport athletes; however little is known about possible underlying changes in functional brain connectivity in this group. We evaluated whole-brain functional connectivity patterns using multi-voxel pattern analysis (MVPA) to determine whether alterations in functional connectivity distinguish retired professional athletes from a matched group of healthy, community control subjects. Thirty-two retired athletes with a history of multiple self-reported sport-related concussions and thirty-six healthy community control subjects, who were similar in age and education, completed functional magnetic resonance imaging (fMRI). We identified brain regions with abnormal functional connectivity patterns using whole-brain multi-voxel pattern analysis (MVPA) as implemented in the Conn toolbox. First level MVPA was performed using 64 PCA components. Second level F test was performed using the first 3 MVPA components for retired athletes > controls group contrast. Post-hoc seed-to-voxel analyses using the MVPA cluster results as seeds were performed to characterize functional connectivity abnormalities from brain regions identified by MVPA. MVPA revealed one cluster of abnormal functional connectivity located in cerebellar lobule V. This region of lobule V corresponded to the ventral attention network. Post-hoc seed-to-voxel analysis using the cerebellar MVPA cluster as a seed revealed multiple areas of cerebral cortical hyperconnectivity and hypoconnectivity in retired athletes when compared to controls. This initial report suggests that cerebellar dysfunction might be present and clinically important in some retired athletes.