Functional changes in the salience network of patients with amnesic mild cognitive impairment before and after repetitive transcranial magnetic stimulation

Abstract

BackgroundAmnestic mild cognitive impairment (aMCI) is considered to be the prodromal stage of Alzheimer's disease (AD). The precuneus (PCUN) may be an imaging marker for monitoring the progression of AD. Meanwhile, cognitive impairment in AD patients is closely related to functional connectivity (FC) changes in the salience network (SN). We hypothesize that there are specific neuroimaging biomarkers in the SN and that FC changes in aMCI patients after repetitive transcranial magnetic stimulation (rTMS) intervention are associated with cognitive function. The purpose of this study was to first investigate the pattern of functional changes in aMCI patients and healthy controls (HCs) and then compare the functional changes in aMCI patients before and after rTMS targeting to PCUN and its correlation with cognitive function.MethodsThirty‐six HCs and 61 aMCIs were recruited for our study. Eleven people in the aMCI group received rTMS intervention 5 days a week for 4 weeks. Using the right anterior insula as the seed‐of‐interest, we first compared FC changes in HC and aMCI patients and then compared cognitive function in aMCI patients before and after rTMS. The above is the functional connection analysis of seed‐to‐voxel. Moreover, we investigated the FC changes in aMCI patients after rTMS intervention and its correlation with cognitive function.ResultsCompared with HC, the aMCI group showed altered FC in bilateral parahippocampal gyrus, bilateral inferior parietal lobule, left middle frontal gyrus, and left middle temporal gyrus. Moreover, rTMS at PCUN improved the cognitive function of aMCI patients, which was related to the altered FC in posterior cerebellar lobes (CPL).ConclusionsOur findings suggest that rTMS targeting PCUN is a promising, noninvasive approach to ameliorating cognitive dysfunction in aMCI patients, and that this cognitive improvement is accompanied by brain connectivity modulation.

rTMS regulates homotopic functional connectivity in the SCD and MCI patients

“…Cognitive changes induced by rTMS may be due not only to modulation of functional brain activity in the stimulated region, but also to indirect effects on other relevant or distant brain regions (Rossi et al, 2001). Prior studies have demonstrated that when the precuneus is stimulated via rTMS, cognitive function can be enhanced through the regulation of brain circuits' plasticity and the reorganization of brain networks; for example, the regulation of precuneus-hippocampal circuits and the salience network (Chen et al, 2020;Yuan et al, 2023). The brain's lateralization in neurodegenerative diseases is linked to cognition and disease progression, indicating that changed connectivity between the hemispheres could be a marker of cognitive decline (Stefanits et al, 2012;Frings et al, 2015).…”

“…The intersection tip of two coil rings was placed at the Pz site to stimulate the Precuneus with the assistance of a 10-20 electroencephalogram system. The rTMS stimulation frequency was 10 Hz (Chen et al, 2020(Chen et al, , 2022Yuan et al, 2023). The Resting State Motor Threshold (RMT) is a measure obtained by stimulating the left motor cortex with the right hand's First Dorsal Interosseous (FDI) muscle in a relaxed state, causing at least 5 of the 10 single pulse stimuli recorded on electromyography to have a motor evoked potential amplitude greater than 50 μV, or at least 5 out of 10 single pulse stimuli to result in FDI twitching in the right hand.…”

“…Previous studies indicate that the homotopic connectivity changes were associated with pathological markers and disease progression (Chen, 2022), implying that the interhemispheric functional connectivity might be a potential imaging marker of disease severity within the AD continuum (Wang et al, 2015). Previous studies have investigated the mechanism of neural network plasticity, such as the DMN and salience network (Yuan et al, 2023) and the precuneus-hippocampus circuits (Chen et al, 2022). These studies employed rTMS to target the precuneus as a means of improving cognitive function.…”

Repetitive transcranial magnetic stimulation regulates effective connectivity patterns of brain networks in the spectrum of preclinical Alzheimer’s disease

“…Each subject received this treatment once a day, five days a week (Monday to Friday), for a duration of two weeks per course of treatment. The entire procedure was repeated for a total of four weeks, equivalent to two treatment courses ( Chen et al, 2021 ; Yuan et al, 2023 ). Subsequently, imaging data acquisition and neuropsychological evaluation were performed for each subject.…”