Altered Functional Connectivity of Cortical Networks and Hippocampus by Transcranial Alternating Current Stimulation in Alzheimer's Disease

Motivation: The potential MRI mechanism by which transcranial alternating current stimulation (tACS) enhances cognition remains unclear. Goal(s): To investigate the efficacy of tACS in modulating functional connectivity (FC). Approach: AD patients were randomly assigned to receive twice-daily, 40 Hz, 15 mA sessions of either active or sham tACS five days per week and over 3 weeks, following by 3-month assessment. Results: Patients in active group achieved greater cognitive improvement than those in sham group at Week 3. There was a significant group×time interaction in increased FC between the left hippocampus and left middle cingulate gyrus, as well as FC within the pDMN and FPN. Impact: fMRI has furnished a precise neuroimaging substrate for the efficacy assessment after tACS, helpful for neurologists to capture neuronal activity modifications. fMRI can elucidate the therapeutic variances and facilitate the refinement of individualized and targeted stimulation protocols for AD patients.