Short-term plasticity in the human brain induced by transcranial electrical stimulation and memory training (Plast-Mem): a multi-modal MRI approach

非侵入性脑刺激（NIBS）技术，如经颅电刺激（tES）和经颅直流电刺激（tDCS）是最常见的方法，已被用于研究脑-行为关系和调节人类认知功能。关于神经元机制，在任务相关的大脑区域，阳极tDCS被认为可以增加皮层的兴奋性，并诱导长期增强（LTP）样过程，从而提高行为任务的表现。tDCS与脑成像技术的结合，无论是连续的还是同时的，都可以表征人脑中大脑活动水平、大脑连通性和代谢物浓度的神经调节。突触和细胞过程反映了体内潜在的结构可塑性，迄今为止已经使用人脑的电生理学和光谱学方法进行了评估。脑灰质和白质的微观结构可塑性是大脑学习相关可塑性的重要标志，但尚未在tDCS背景下进行评估。为此，本项目的主要目的是利用多模态磁共振成像技术研究tdcs支持的人脑记忆训练在微观结构和神经代谢物浓度水平上的短期大脑结构可塑性。我们将在目标位置记忆范式中对颞顶叶部位应用焦点（高清）节点tDCS，并在训练前、训练后（工作包1，WP1）和训练后12小时（WP2）获取多模态MRI，使用记忆相关网络枢纽和白质通路的DTI指标评估微结构可塑性，并使用MRS作为神经元功能标记的代谢物浓度。此外，还将研究微观结构和代谢可塑性的相互依赖性（WP3），以及使用计算模型估计的行为和功能网络效应与单独感应电场的联系（WP4）。该项目将促进对tdcs诱导的可塑性的全面理解，并支持未来针对认知系统的个性化调整应用的发展。

Non-invasive brain stimulation (NIBS) techniques such as transcranial electrical stimulation (tES) with transcranial direct current stimulation (tDCS) as the most common approach, have been used to examine brain-behavior relationships and modulate human cognitive function. With regard to neuronal mechanisms, anodal tDCS over task-relevant brain regions is thought to increase excitability of the cortex and induce long-term potentiation (LTP)-like processes, leading to enhancement in behavioral task performance. The combination of tDCS with brain imaging techniques, either consecutively or concurrently, has allowed characterization of neural modulation on the levels of brain activity, brain connectivity and metabolite concentrations in the human brain. Synaptic and cellular processes, reflecting underlying the structural plasticity in vivo, have been assessed so far using electrophysiology and spectroscopy approaches in the human brain. Microstructural plasticity in brain gray and white matter, an important marker of learning-related plasticity in the brain, has not been assessed in the context of tDCS yet. To this end, the superordinate aim of this project is to investigate short-term structural brain plasticity on the level of microstructure and neurometabolite concentrations of tDCS-supported memory training in the human brain using multi-modal MR imaging. We will apply focal (high-definition) anodal tDCS over temporo-parietal sites during an object-location memory paradigm and acquire multi-modal MRI before, immediately after (work package 1, WP1) and 12-hours after training (WP2) to assess microstructural plasticity using DTI metrics in memory-related network hubs and white matter pathways and metabolite concentrations using MRS as markers for neuronal function. The inter-dependency of microstructural and metabolic plasticity will additionally be investigated (WP3), together with the linkage of behavioral and functional network effects to individually induced electric fields estimated using computational modeling (WP4). This project will advance the comprehensive understanding of tDCS-induced plasticity and support the development of individually adjusted applications to target cognitive systems in the future.