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）与经颅直流电刺激（tDCS）作为最常见的方法，已被用来检查大脑行为的关系和调节人类的认知功能。关于神经元机制，在任务相关的大脑区域上的阳极tDCS被认为增加皮层的兴奋性并诱导长时程增强（LTP）样过程，从而导致行为任务表现的增强。tDCS与脑成像技术的组合，无论是连续或同时，允许表征的神经调制的水平上的脑活动，脑连接和代谢物的浓度在人脑中。突触和细胞的过程，反映了潜在的结构可塑性在体内，迄今已被评估，在人脑中使用电生理学和光谱学方法。大脑灰质和白色物质的微结构可塑性是大脑中学习相关可塑性的重要标志，尚未在tDCS的背景下进行评估。为此，该项目的最高目的是使用多模态MR成像研究tDCS支持的人脑记忆训练的微观结构和神经代谢物浓度水平上的短期结构脑可塑性。我们将在对象位置记忆范例期间对颞顶叶部位应用局灶性（高清晰度）阳极tDCS，并在训练前、训练后立即（工作包1，WP 1）和训练后12小时（WP 2）获取多模态MRI，以使用记忆相关网络中心和白色物质通路中的DTI指标评估微结构可塑性，并使用MRS作为神经元功能标记物评估代谢物浓度。此外，还将研究微观结构和代谢可塑性的相互依赖性（WP 3），以及使用计算建模（WP 4）估计的行为和功能网络效应与单独诱导电场的联系。该项目将促进对tDCS诱导的可塑性的全面理解，并支持未来针对目标认知系统开发单独调整的应用程序。

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.