Abstract: Motivated Forgetting is an important aspect of effective memory system. People have motivations to limit the time they spend thinking about unpleasant experiences, thus they eventually forget those memories. TNT, think/no-think paradigm is proposed to study the process of motivated forgetting based on go/no-go experimental paradigm. This paradigm emphasizes individuals' subjective suppression of unwanted memories reduces their later conscious recall. In recent years, a plenty of TNT behavioral studies have consistently indicated that memory suppression can produce negative control effect, thus verify the feasibility of the implementation of motivated forgetting in a laboratory context. In this review, we summarized some main characteristics of negative control effect in order to help future research implemented by TNT could obtain the inhibitory control processes to study motivated forgetting. Recent discussion on the neural mechanisms of motivated forgetting has accumulated a great deal of research evidences. Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are two widely used brain techniques to determine these inhibitory control processes of motivated forgetting. First, ERP studies of motivated forgetting using TNT paradigm have revealed a smaller Parietal Episodic Memory effect, appears 400-800 ms after target stimulus onset during the memory retrieval suppression. What’s more, ERP evidences have indicated that N2, which indexes cognitive control are larger during retrieval suppression. Recent EEG studies of motivated forgetting have revealed an increase of alpha and theta oscillations of memory suppression. More interestingly, fMRI evidences have showed that suppressing awareness of an unwelcome memory was achieved by inhibitory control processes mediated by the lateral prefrontal cortex. These mechanisms interact with brain regions that represent experiences in memory, disrupting traces that support retention. Moreover, suppressing retrieval of unwanted memories not only modulates medial temporal lobe regions involved in explicit retention, but also neocortical areas underlying unconscious expressions of memory. However, considering EEG and fMRI measure different aspect of brain activities, the neural mechanism revealed by fMRI and electrophysiology indices supported by EEG of motivated forgetting needs an integrated review. In this review, we firstly summarized current existing TNT researches using EEG and fMRI techniques, and then proposed a multi-modal functional network model of motivated forgetting. In this model, we suggested some potential relationship between the neural mechanism revealed by fMRI and electrophysiology indices supported by EEG. Therefore, our multi-modal functional network model provided a more comprehensive understanding of inhibitory control processes of motivated forgetting. Based on this model, we then outlined some future research directions of TNT paradigm. Most importantly, we think the application of simultaneous EEG-fMRI technology is expected to reveal the dynamic process of motivated forgetting induced by memory suppression. Finally, because the ability of memory inhibition can represent individual’s mental health, future research on the neural mechanisms of motivated forgetting will have broad clinical applications. The purpose of this review, obviously, is to give a more integrated perspective of current researches of motivated forgetting used TNT paradigm. However, far more work need to be done to test our multi-modal functional network model of motivated forgetting.

Key words: think/no think, TNT negative control effect memory retrieval suppression EEG fMRI

摘要： 想/不想范式(Think/No-think, TNT)是基于go/no-go范式提出来的用于研究动机性遗忘过程的实验范式，主要过程是指个体对于记忆的提取抑制可以导致随后该记忆的遗忘。近年来TNT范式的大量行为学研究都一致性地发现记忆提取抑制可以产生负性控制效应，验证了在实验室情境下对动机性遗忘进行研究的可行性。其中，负性控制效应指的是压抑条件的项目相对于基线条件的项目的回忆量有显著降低。关于动机性遗忘发生的神经机制的探讨已积累了大量的研究证据，总结脑电(EEG)和功能核磁共振(fMRI)两个模态的研究，我们提出了动机性遗忘发生的多模态功能网络模型。最后，在该模型的基础上，我们展望了TNT范式未来的研究方向，其中特别注意到同步EEG-fMRI技术的应用有望为我们揭示出记忆提取抑制导致的动机性遗忘发生的动态过程。

关键词: Think/No-think，TNT 负性控制效应 记忆提取抑制 脑电 功能核磁共振