RESTING STATE CONNECTIVITY RELATED TO APATHY IN MILD COGNITIVE IMPAIRMENT

Abstract

Apathy is a common neuropsychiatric symptom in patients with amnestic mild cognitive impairment (aMCI) and has been associated with progression to Alzheimer's disease. Apathy is defined as diminished voluntary goal-directed behavior leading to decreased motivation and interest. There are two preliminary studies that have investigated resting state functional connectivity related to apathy in aMCI (Joo e.a. 2016; Munro e.a. 2015). However, neither of them used a complete data-driven approach, therefore the neural basis of apathy in aMCI needs further investigation. Thirty-one patients with aMCI and 20 healthy controls (HC) were assessed with resting state fMRI. Apathy was assessed with the apathy evaluation scale (clinician version, AES-C). Independent component analysis (ICA) was used to determine the brain networks. We were specifically interested in the default mode network (DMN), fronto-parietal network (FPN), salience network (SN) and basal ganglia network (BGN). Both within- and between-network connectivity was investigated. We performed a group comparison between patients and HC, and a regression analysis with AES score in aMCI patients only. Threshold was set at p<.05 family wise error corrected for multiple comparisons on cluster level, with an initial threshold of p<.001. Two components were identified as DMN, two components as FPN, four components as SN and one as BGN. aMCI patients showed stronger within-network functional connectivity compared to HC in the FPN. Moreover, MCI patients had weaker connectivity between an SN and DMN component. Apathy was related to decreased connectivity between the SN and DMN and increased connectivity between two SN components (one including mostly dorsal anterior cingulate cortex [dACC] and the other mostly the insula). Salience detection is an important component for goal-directed behavior. Therefore, it is interesting that levels of apathy in aMCI were associated with altered connectivity related to the SN. Especially, disturbances in the dACC have consistently been associated with apathy in aMCI. Therefore, it might be suggested that these disturbances in the dACC lead to changes in connectivity to other brain areas/networks. The next step in the analyses will be to investigate the network properties related to apathy using graph theory and independent components as data-driven nodes.