The impact of non-invasive stimulation of the ventromedial prefrontal cortex on attentional biases and reward processing: an advanced network approach

本研究的首要目标是阐明腹内侧前额叶皮层（vmPFC）在情绪材料和奖励处理中的主要作用。我们打算把重点放在vmPFC“在工作”时，当它偏向于情绪和奖励处理时，直接追踪它的激活，特别是追踪它与其他皮质区域的功能关系。到目前为止，关于这两种偏见背后的神经机制的证据主要是基于相关方法和对分离时特定大脑区域的分析。相比之下，我们计划直接和非侵入性地调节vmPFC的兴奋性，并计划引入一种新的网络连接方法，使我们能够在神经信息交换过程中跟踪功能性脑回路。我们认为vmPFC通过双向反馈和前馈连接来调节大脑的其他区域并接受它们的调节。基于现有文献和德国和波兰研究小组的前期工作，我们预测vmPFC与其他脑区（特别是背外侧前额叶和颞顶叶皮层区域）以及与背侧和腹侧注意网络的功能连接之间的动态相互作用将反映出注意偏差和奖励加工的神经机制。在我们的实验中，我们将无创经颅直流电刺激（tDCS）与EEG/MEG方法相结合，以增加和减少vmPFC的兴奋性，并以高时间分辨率监测大脑活动。我们将采用源定位方法，以良好的空间分辨率重建特定大脑结构的激活。重要的是，为了确定注意偏差和奖励处理过程中大脑区域之间的动态关系，将使用定向传递函数（DTF）有效连接进行因果分析，这是一种由波兰小组成功使用并不断开发的创新网络方法。这个项目的结果将促进当前对注意偏差和奖励处理的神经基础的理解。特别是，我们的目标是揭示vmPFC在这些偏差中的动态作用。由于情绪注意和奖励处理中的干扰偏差被认为是包括抑郁或成瘾在内的各种精神疾病的关键症状，因此本项目的结果将为相应的病理生理学理论提供信息。同时，通过采用DTF，我们将开发一种新的源空间MEG数据分析管道。只有在两个小组的密切合作下才能实现项目的目标。德国团队提供MEG-tDCS研究实施方面的专业知识，而波兰团队提供传感器和源空间有效连接分析方面的专业知识。该联合项目将促进知识和技能的转移，并进一步加强双方的合作。

The overarching goal of the proposed research project is to illuminate the presumed cardinal role of the ventromedial prefrontal cortex (vmPFC) on the processing of emotional material and reward. We intend to focus on the vmPFC "at work", while it biases emotional and reward processing, to directly trace its activation but especially trace its functional relationships with other cortical areas. Until now, evidence for the neural mechanisms underlying both types of biases was predominately based on correlational approaches and analyses of particular brain areas in separation. In contrast, we plan to directly and non-invasively modulate vmPFC excitability and plan to introduce a novel network connectivity approach that enables us to track functional brain circuits during exchange of neural information.We propose that the vmPFC modulates other brain regions and gets modulated by them via bidirectional feedback and feedforward connections. Based on the existing literature and previous work of the German and Polish groups, we predict, that neural mechanisms of attentional bias and reward processing will be reflected by a dynamic interaction between vmPFC and other brain areas, specifically dorsolateral prefrontal and temporoparietal cortex regions as well as functional connectivity with the dorsal and ventral attentional networks.In our experiments, we will combine non-invasive transcranial direct-current stimulation (tDCS) with EEG/MEG methodology to increase and decrease vmPFC excitability and monitor brain activity with high temporal resolution. We will employ source localization methods that reconstruct activations of particular brain structures with good spatial resolution. Importantly, to determine dynamic relationships across brain regions during attentional bias and reward processing, causal analyses will be performed using the Directed Transfer Function (DTF) effective connectivity, an innovative network approach which is successfully used and constantly developed by the Polish group.The results of this project will advance current understanding of the neural underpinnings of attentional biases and reward processing. In particular, we aim to unravel the dynamic role of vmPFC during these biases. As disturbed biases in emotional attention and reward processing are considered key symptoms of various psychiatric disorders including depression or addiction, the results of this project will inform theories of corresponding pathophysiology. At the same time, by employing DTF, we will develop a novel pipeline for the analysis of the source-space MEG data.The projects objectives and goals can only be achieved in close collaboration between both groups. The German group provides expertise in implementation of MEG-tDCS studies while the Polish group provides expertise in effective connectivity analyses in sensor and source space. The joint project will enable transfer of knowledge and skills and further strengthen the collaboration of both groups.