Dysfunctional organization of default mode network before memory impairments in type 2 diabetes

Aims: Episodic memory depends on the maintenance of an intact default mode network (DMN), and is one of the earliest cognitive domains, to become impaired in type 2 diabetes mellitus (T2DM). Therefore, exploring the alterations in task-related DMN deactivation and functional connectivity that affect episodic memory in T2DM will help to enhance our understanding of the allocation patterns underlying memory function in T2DM. Methods: The current study assessed changes in DMN activation and architecture during the encoding of a functional magnetic resonance imaging task in 39 patients with T2DM and 41 healthy controls which were recruited from local communities in Beijing, China. Results: We found that patients with T2DM and intact episodic memory performance exhibited reduced deactivation in the right precuneus and the middle temporal gyrus during the episodic memory task. Furthermore, an anterior-posterior disconnection phenotype and altered topological configuration of the DMN were observed in patients with T2DM using graph-theoretical approaches. Correlation analysis showed that altered deactivation during the episodic memory task was closely related to connectivity dysfunction and topological properties in the DMN. Conclusions: Our findings demonstrate that the maintenance of memory in patients with T2DM involves reduced deactivation and impaired anterior-posterior connections in the DMN during encoding. (C) 2016 Elsevier Ltd. All rights reserved.