Function and relevance of oscillatory prestimulus activity for the formation of memory

近年来，一些研究已经证明了在实际刺激出现之前，特定的大脑活动与一些认知过程的相关性，正如在自己的试点研究中一样，其他研究也表明了不同神经元刺激前活动对记忆形成的影响。总之，不同频率的振荡活动与随后处理刺激的记忆质量有关。然而，目前还不清楚不同的活动代表了什么样的心理因素，以及不同的振荡与记忆形成的相关性有多强。据推测，不同的因素影响的刺激前活动，但至少有一个因素应该是具体的后续信息处理，并应纳入作为一个相关的过程的记忆过程。以前的研究的实验设计使用的线索，告知参与者的实际刺激的呈现，从而使实际的刺激处理有意识的准备。因此，刺激前活动也是一种线索诱发活动，反映了不同的过程，如注意，动机和特定的编码策略。实际项目的目的是识别不同的心理因素和分化的神经元效应。将不同频段的神经元效应分配给心理描述的信息加工因素，需要通过线索刺激信息的存在和操纵来实现，因此，通过指令操纵线索信息，从而影响注意或编码策略激活等差异性加工。不同过程的神经相关性将通过EEG测量进行评估。与无提示刺激的实验环境的比较对于确定相关的刺激前活动而不受提示诱发活动的影响是很重要的。所用材料的刺激前期内神经元活动的特异性将通过分析听觉和视觉记忆形成的共同和不同效应来估计。不同过程的功能相关性将通过良好的适应性刺激呈现来测试。描述了神经元活动的状态，并通过使用神经反馈方法与已经建立的脑-计算机接口来调节神经元活动。最后，相关振荡的神经源将通过组合的EEG-fMRT测量更详细地估计。

In the recent years the relevance of specific brain activity before the presentation of the actual stimulus has been demonstrated in several studies and for several cognitive processes.As in an own pilot study also other studies have shown an influence of different neuronal prestimulus activity also for the formation of memory. In summary, oscillatory activity in different frequencies was related to the quality of memory for the subsequent processed stimulus. However, it remains unclear what psychological factors were represented by the different activities and how strong the relevance of the different oscillations is for the formation of memory. It is postulated that different factors affected the prestimulus activity but that at least one factor is supposed to be specific for the subsequent information processing and should be incorporated as a relevant process for the memory process. The experimental designs of previous studies used cues that informed the participants about the presentation of the actual stimulus and thereby enabled a conscious preparation for the actual stimulus processing. Therefore, the prestimulus activity is also a cue evoked activity and reflects different processes like attention, motivation and specific encoding strategies.The aim of the actual project is the identification of the different psychological factors and the differentiation of the neuronal effects. The assignment of neuronal effects in different frequency bands to psychological described information processing factors should be achieved by the presence and manipulation of the information of cue stimuli.Therefore, the information of the cue is manipulated via the instruction to influence differentially processes like attention or the activation of encoding strategies. The neural correlates of the different processes will be assessed with EEG measurements. The comparison to experimental settings without a cue stimulus is important to determine relevant prestimulus activity without the influence of cue evoked activity.The specificity of the neuronal activity within the prestimulus period for the used material will be estimated by the analysis of common and different effects for acoustic and visual memory formation.The functional relevance of the different processes will be tested by adaptive stimulus presentation in well described states of neuronal activity and by modulation of neuronal activity using neurofeedback approaches with an already established brain- computer interface. Finally, the neuronal sources of the relevant oscillations will be estimated by combined EEG- fMRT measurements in more detail.