Wang Yuejuan, De Weerd Peter, Sack Alexander T, van de Ven Vincent
Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.
Imaging Neurosci (Camb). 2024 Oct 24;2. doi: 10.1162/imag_a_00332. eCollection 2024.
Temporal memory plays a crucial role in organizing real-life events into meaningful segments. Previous research suggests that the clustering of temporally related information builds on the neural correlates of associative memory, including theta oscillations. Transcranial alternating current stimulation (tACS) provides a means of modulating theta oscillations within associative memory networks, possibly including hippocampal modulation when targeting the parietal cortex. Theta oscillations are not limited to a single frequency range, but instead, exhibit functional specialization, with slow theta (3 Hz) implicated in short-term episodic memory formation and fast theta (8 Hz) involved in spatial navigation. Our study aimed to investigate the distinct effects of slow and fast theta stimulation on temporal memory. Participants encoded visual objects paired with frame color while receiving tACS stimulation at 3 Hz, 8 Hz, or sham targeting the left parietal cortex. The frame color would change after every eight objects, establishing a context boundary with each color change. Subsequently, participants performed a timeline task to assess temporal memory performance. Results showed that slow, but not fast, theta stimulation led to an enhancement in temporal accuracy (absolute temporal error) compared to sham tACS, in support of our main hypothesis. Under sham stimulation, participants consistently underestimated the temporal position of items presented further away from boundary, compared to those presented at boundary. This finding resembled temporal compression observed during event segmentation. Interestingly, fast, but not slow, theta stimulation reduced this temporal bias (rated position-actual position). This study represents the first tACS evidence for differential contributions of slow versus fast theta to temporal memory formation in humans. We speculate that parietal theta tACS may modulate the hippocampus and facilitate temporal memory formation.
时间记忆在将现实生活事件组织成有意义的片段中起着至关重要的作用。先前的研究表明，时间相关信息的聚类建立在联想记忆的神经关联基础上，包括theta振荡。经颅交流电刺激（tACS）提供了一种调节联想记忆网络中theta振荡的方法，当针对顶叶皮层时可能包括对海马体的调节。theta振荡不限于单一频率范围，而是表现出功能特化，慢theta（3Hz）与短期情景记忆形成有关，快theta（8Hz）与空间导航有关。我们的研究旨在调查慢theta和快theta刺激对时间记忆的不同影响。参与者在接受针对左顶叶皮层的3Hz、8Hz或假刺激的同时，对与框架颜色配对的视觉对象进行编码。每八个对象后框架颜色会改变，每次颜色变化建立一个情境边界。随后，参与者执行一项时间线任务以评估时间记忆表现。结果表明，与假tACS相比，慢theta刺激而非快theta刺激导致时间准确性（绝对时间误差）提高，支持了我们的主要假设。在假刺激下，与边界处呈现的项目相比，参与者一致低估了远离边界呈现的项目的时间位置。这一发现类似于事件分割过程中观察到的时间压缩。有趣的是，快theta刺激而非慢theta刺激减少了这种时间偏差（评定位置-实际位置）。这项研究代表了第一项关于慢theta与快theta对人类时间记忆形成的不同贡献的tACS证据。我们推测顶叶theta tACS可能调节海马体并促进时间记忆形成。
