Brain network modulation in Alzheimer's and frontotemporal dementia with transcranial electrical stimulation

The default mode (DMN) and the salience (SN) networks show functional hypo-connectivity in Alzheimer's disease (AD) and the behavioral variant of frontotemporal dementia (bvFTD), respectively, along with patterns of hyper-connectivity. We tested the clinical and neurobiological effects of noninvasive stimulation over these networks in 45 patients (AD and bvFTD) who received either anodal (target network: DMN in AD, SN in bvFTD) or cathodal stimulation (target network: SN in AD, DMN in bvFTD). We evaluated changes in clinical, cognitive, functional and structural connectivity, and perfusion measures. In both patient groups, cathodal stimulation was followed by behavioral improvement, whereas anodal stimulation led to cognitive improvement. Neither functional connectivity nor perfusion showed significant effects. A significant interaction between DMN and SN functional connectivity changes and stimulation protocol was reported in AD. These results suggest a protocol-dependent response, whereby the protocols studied show divergent effects on cognitive and clinical measures, along with a divergent modulatory pattern of connectivity in AD. (C) 2021 The Authors. Published by Elsevier Inc.

Automated summary

The default mode and salience networks in Alzheimer's disease and behavioral variant of frontotemporal dementia exhibit different patterns of functional connectivity and modulatory effects. Anodal stimulation improves cognition, while cathodal stimulation improves behavior. Neither functional connectivity nor perfusion measurements show significant effects in both patient groups. The changes in functional connectivity between DMN and SN in AD are dependent on the stimulation protocol.