Electrical field strength from anodal prefrontal tDCS determines degree of white matter integrity changes in amnestic MCI patients

Abstract

AbstractBackgroundAn electrical field (EF) strength induced by tDCS affects a therapeutic effect. Additionally, sequential tDCS has improved white matter integrity in cognitively impaired patients. However, researchers have not evaluated the impact of EF strength on white matter integrity in the prodromal stage of dementia. This study aimed to elucidate the effect of EF strength from prefrontal anodal tDCS on white matter integrity change and the modulating role of relevant genetic and pathologic factors in this effect in amnestic mild cognitive impairment (MCI) patients.MethodIn 55 amnestic MCI patients, we delivered anodal‐tDCS (2 mA/day, five times/week, for two weeks) over the left dorsolateral prefrontal cortex (DLPFC), calculated the EF strength for the left inferior frontal gyrus and DLPFC through the stimulation navigation program analysis. Additionally, we assessed the white matter integrity by diffusion tensor imaging before and after two weeks of stimulation; finally, we evaluated the modulating factors: amyloid‐beta (Aβ) deposition, APOE ε4‐allele status, and BDNF polymorphism.ResultAs the EF intensity in the left inferior frontal gyrus increased, the range of changes in white matter integrity significantly increased in left anterior thalamic radiation, corticospinal tract, inferior fronto‐occipital fasciculus, and inferior longitudinal fasciculus. Additionally, we found that greater change in white matter integrity was observed with higher regional EF strength in the APOE ε4 non‐carriers and BDNF MET non‐carrier, which could be attributed to an interaction between these modulating factors and EF intensity in the left anterior thalamic radiation and right uncinate fasciculus.ConclusionThese findings provide evidence for the precision‐medicine‐based application of tDCS in the prodromal stage of dementia, inducing the optimized therapeutic effect.