Altered organization of the dorsal attention network is associated with freezing of gait in Parkinson's disease

Introduction: Deficits in executive function and attention have been associated with freezing of gait (FOG) in patients with Parkinson's disease (PD). However, the exact changes in the ventral and dorsal attentional networks that may contribute to FOG are unknown. Our aim was to examine the changes in connectivity of the attentional networks in patients with PD and their role in FOG. Methods: Resting-state fMRI was obtained in 20 healthy controls (age: 69.7 +/- 1.3yrs), 11 patients without FOG (age: 74.1 +/- 1.2yrs), and 26 patients with FOG (age: 72.3 +/- 1.3yrs). Graph theory analysis was used to examine differences in previously defined attention networks between groups. Results: We found differences between the groups in the dorsal attentional network (Global Efficiency: p = 0.007, Local Efficiency: p = 0.017, Between Centrality: p = 0.010). Global efficiency was lower in patients with FOG compared to healthy controls (p = 0.003) and patients without FOG (p = 0.025). Local efficiency was higher in patients with FOG compared to healthy controls (p = 0.014) but not compared to patients without FOG (p = 0.109). In contrast, no differences were found in the ventral attentional network between the groups (Global Efficiency: p = 0.258, Local Efficiency: p = 0.114, Between Centrality: p = 0.130). Conclusions: Altered organization of the dorsal attention network in patients with FOG may explain the higher risk for FOG during complex walking situations. In contrast, the lack of changes in the ventral attention network may partially explain the effectiveness of external cues on gait in patients with PD. Our findings support the idea that attentional networks play an important role in FOG.