Network Patterns of Beta-Amyloid Deposition in Parkinson's Disease

Beta-amyloid (A beta) in the brain is a key pathological feature of certain neurodegenerative diseases. Recent studies using graph theory have shown that A beta brain networks are of pathological significance in Alzheimer's disease (AD). However, the characteristics of A beta brain networks in Parkinson's disease (PD) are unknown. In the present study using positron emission tomography (PET) with [C-11]-Pittsburgh compound B (PiB), we applied a graph theory-based analysis to assess the topological properties of A beta brain network in PD patients with and without A beta burden (PiB-positive and PiB-negative, respectively) and healthy controls with A beta burden. We found that the PD PiB-positive group demonstrated significantly lower value in global efficiency and modularity compared with PD PiB-negative group. The less robust modular structure indicates the tendency of having increased inter-modular connections than intra-modular connectivity (i.e., reduced segregation). Results of hub organization showed that relative to PD PiB-negative group, different hubs were identified in the PiB-positive group, which were located mainly within the default mode network. Overall, our findings suggest disturbances in A beta topological organization characterized by abnormal network integration and segregation in PD patients with A beta burden. The stronger inter-modular connectivity observed in the PD PiB-positive group may suggest the spreading pattern of A beta between modules in those PD patients with elevated PiB burden, thus providing insight into the beta-amyloidopathy of PD.