Relevance of neuronal pre-stimulus oscillatory activity for the formation of crossmodal episodic memory

对于几个认知过程，研究表明，在刺激呈现之前的神经元活动调节该刺激的连续处理。对于记忆的形成，我们的团队和其他几名研究人员证明了前刺激振荡活动对记忆编码的显着影响。这种效应主要表现在以一种方式呈现的项目记忆上。然而，现实世界中情节记忆的一个关键特征是不同感觉形式的整合。因此，本提案的目的是研究刺激前振荡活动对形成跨模式联系的功能作用。基于理论假设和以前的观察，我们假设了theta频段(4-8赫兹)振荡活动的功能相关性。包括幅度和相位锁定在内的前刺激theta频段特征被假设为对来自不同感觉模式的信息的关联的记忆编码的预测性。此外，还将考察刺激前后活动对记忆形成的交互作用。已经开发和测试的实验设计允许评估视觉和听觉刺激之间的纯联想记忆，而不依赖于对单个刺激的记忆。在提案的第一部分，将使用脑电测量来检查视听记忆的形成。在这里，将检查刺激前的theta带幅度和相位耦合的相关性，以及这两个参数与刺激后处理的关系。理论模型假设不同感觉通道对海马区的一致输入是通过theta带振荡活动实现的。在第二部分中，将使用脑电和功能磁共振联合测量来检验这一假设。在这里，我们检验了这一假设，即theta带前刺激活动影响了海马区内的连续加工。对跨感觉情景记忆的神经元关联的检查应该反映出这些记忆通常产生的丰富环境。因此，在第三部分中，计划在更逼真的虚拟现实(VR)环境中测试实验室结果的可靠性和有效性。在现实世界中，情节记忆是在自然环境中编码的，通常是记忆的一部分。VR设置非常适合测试更自然的背景记忆的编码和在该背景下跨通道联想的发展。此外，参与者的行为可以在VR中被详细记录，以将行为方面与记忆的形成联系起来。在这里，计划测试自我投入行为和探索行为(头部和眼球运动)对刺激前振荡状态和记忆编码的影响。因此，在最后的实验中，脑电的测量将与VR刺激同步进行。

For several cognitive processes it was demonstrated that the neuronal activity prior to stimulus presentation modulates the consecutive processing of that stimulus. For memory formation our group and several other researchers demonstrated a pronounced influence of pre-stimulus oscillatory activity on memory encoding. This effect was mainly demonstrated for item memory presented in one modality. However, a key feature of episodic memory in the real world is the integration of different sensory modalities. Therefore, the aim of the present proposal is the examination of the functional role of pre-stimulus oscillatory activity for the formation of crossmodal associations. Based on theoretical assumptions and previous observations we hypothesize a functional relevance of oscillatory activity in the theta-band (4-8 Hz). The pre-stimulus theta band characteristics including amplitude and phase locking are hypothesized to be predictive for memory encoding for associations of information from different sensory modalities. Furthermore, the interactive effect of pre- and poststimulus activity for memory formation will be examined. The already developed and tested experimental design allows for assessing pure associative memory between visual and auditory stimuli independent from the memory for the individual stimuli. In the first section of the proposal audio-visual memory formation will be examined using EEG- measurements. Here, the relevance of pre-stimulus theta band amplitude and phase coupling and the relation of both parameters to post-stimulus processing will be examined. Theoretical models assumes that the coincident input from different sensory modalities to the hippocampus is realized by theta- band oscillatory activity. In the second section this assumption will be tested using combined EEG- and fMRI measurements. Here, the hypothesis is tested that theta-band pre-stimulus activity affects the consecutive processing within the hippocampus.The examination of the neuronal correlates of cross-sensory episodic memory should reflect the rich environment in which these memories are generated usually. Therefore, in the third section it is planned to test the reliability and validity of the laboratory results in a more realistic virtual reality (VR) setting. In the real world episodic memory is encoded in a natural context with is usually part of the memory. The VR setting is perfectly suited to test the encoding of more naturalistic contextual memory and the development of crossmodal association within that context. Furthermore, the behavior of the participants can be recorded in VR in detail to relate behavioral aspects to the formation of memory. Here, it is planned to test the influence of self-engaged actions and exploratory behavior (head- and eye-movements) on the pre-stimulus oscillatory state and memory encoding. Therefore, EEG will be measured simultaneously with the VR- stimulation in the last experiments.