Functional Connectivity Correlates of Reduced Goal-directed Behaviors in Behavioural Variant Frontotemporal Dementia

Abstract INTRODUCTION: We explored the resting state functional connectivity correlates of apathy assessed as a multidimensional construct, using behavioral metrics, in behavioral variant frontotemporal dementia (bvFTD).METHODS: We recorded the behavior of 20 bvFTD patients and 16 healthy controls (HC) in a close-to-real-life situation including a free phase (FP – in which actions were self-initiated) and a guided phase (GP – in which initiation of actions was facilitated by external guidance). We investigated the activity time and walking episode features as quantifiers of apathy. We used the means ((FP+GP)/2) and the differences (FP-GP) calculated for these metrics as well as measures by questionnaires to extract apathy dimensions by factor analysis. We assessed two types of connectivity measures (local low-frequency signal power and distant seed-based functional connectivity) and explored their relationship with extracted apathy dimensions. RESULTS: Apathy in bvFTD was associated with lower time spent in activity combined with walking episodes of higher frequency, lower acceleration and higher duration. Using these behavioral metrics and apathy measures by questionnaires, we disentangled two dimensions: the global reduction of goal-directed behaviors and the specific deficit of selfinitiation. Global apathy was associated with lower resting state activity within prefrontal cortex and lower connectivity of salience network hubs while the decrease in self-initiation was related to increased connectivity of parietal default-mode network hubs. DISCUSSION: Through a new dimensional approach of apathy, we dissociated the functional connectivity correlates of global apathy and self-initiation deficit. This contributes to better understand the role of functional networks in the production of goal-directed behaviors.