Functional network connectivity in the behavioral variant of frontotemporal dementia

Abstract

Introduction: The aim of this study was to investigate, using resting state (RS) functional magnetic resonance imaging (fMRI), the functional connectivity within and among brain networks in patients with the behavioral variant of frontotemporal dementia (bvFTD), compared with healthy controls and patients with probable Alzheimer's disease (pAD).

Methods: Twelve bvFTD patients were compared with 30 controls and 18 pAD patients. Functional connectivity within the salience, default mode (DMN), executive (EXN), attention/working memory (ATT/WM), and dorsal attentional networks was assessed using independent component analysis. The temporal associations among RS networks (RSNs) were explored using the functional network connectivity toolbox.

Results: A decreased dorsal salience network (DSN) connectivity, mainly involving the anterior cingulum, was observed in bvFTD versus controls and pAD. BvFTD was also characterized by a decreased ventral salience network connectivity in the basal ganglia, and divergent connectivity effects versus controls in the dorsolateral prefrontal cortex (decreased) and precuneus (enhanced) within the right ATT/WM network. The dorsal attentional network had a decreased connectivity with the DMN and EXN in bvFTD versus controls, and a decreased connectivity with the DSN versus pAD.

Conclusions: RSN functional abnormalities occur in bvFTD, involving not only the salience network, but also the DMN and fronto-parietal network associated with ATT and WM modulation. The pattern of functional changes differs from that seen in pAD. The altered interactions among RSN observed in bvFTD and pAD may provide a new venue to explore the functional correlates of cognitive abnormalities in neurodegenerative and psychiatric disorders.

Keywords: Alzheimer's disease; Behavioral variant of frontotemporal dementia; Default mode network; Resting state functional MRI; Salience network.