Associating Resting-State functional connectivity and improvements in reactive balance in Parkinson's Disease.

Reactive stepping is impaired in people with Parkinson's disease (PwPD) and can be trained through practice. However, these improvements are often variable across individuals. Identifying neurological predictors and potential mechanisms of this variability can improve the efficiency of rehabilitation. This study investigated the association between improvements in backward reactive stepping performance through training and resting-state functional magnetic resonance imaging (rs-fMRI) in PwPD. 16 PwPD underwent rs-fMRI and an eighteen-week multiple-baseline study, which included baseline assessments (B1 and B2, 2-weeks apart), a 2-week training protocol, and post-training assessments immediately after protocol (P1) and 2-months later (P2), in which we assessed anterior-posterior margin of stability (MOSAP) at first foot contact. Linear regression analyses assessed the relationship between functional connectivity, using a region of interest approach, and immediate (P1-B2) and retained (P2-B2) improvements in MOSAP during reactive stepping. Results showed that higher right thalamus-right amygdala connectivity was related to immediate MOSAP improvements (pFDR < 0.05). Right thalamus-right amygdala, left caudate-left hippocampus, and left thalamus-left hippocampus connectivity were associated with better long-term retention of MOSAP (pFDR's < 0.05). These findings suggest thalamo-limbic coupling may contribute to immediate and retained improvements in reactive balance in PwPD and could aid in identifying individuals who would benefit most from balance rehabilitation.