Xie Weizhen, Thakurdesai Sanikaa, Varastegan Sahereh, Zhang Weiwei
Department of Psychology, University of Maryland, College Park, Maryland, USA.
Department of Psychology, University of California, Riverside, California, USA.
Hippocampus. 2025 Jan;35(1):e23678. doi: 10.1002/hipo.23678.
Although the medial temporal lobe (MTL) is traditionally considered a region dedicated to long-term memory, recent neuroimaging and intracranial recording evidence suggests that the MTL also contributes to certain aspects of visual short-term memory (VSTM), such as the quality or precision of retained VSTM content. This study aims to further investigate the MTL's role in VSTM precision through the application of transcranial direct current stimulation (tDCS) and functional magnetic resonance imaging (fMRI). Participants underwent 1.5 mA offline tDCS over bilateral temporal lobes using left cathodal and right anodal electrodes, administered for either 20 min (active) or 0.5 min within a 20-min window (sham), in a counterbalanced design. As the electrical current passes through midbrain structures with this bilateral stimulation montage, prior behavioral and modeling evidence suggests that this tDCS protocol can modulate MTL functions. To confirm this and examine its impacts on VSTM, participants completed a VSTM color recall task immediately following tDCS, while undergoing a 20-min fMRI scan and a subsequent 7.5-min resting-state scan, during which they focused on a fixation cross. Behavioral results indicated that this tDCS protocol decreased VSTM precision without significantly affecting overall recall success. Furthermore, psychophysiological interaction analysis revealed that tDCS over the temporal lobe modulated hippocampal-occipital functional connectivity during the VSTM task, despite no main effect on fMRI BOLD activity. Notably, this modulation was also observed during resting-state fMRI 15-20 min post-tDCS, with the magnitude of the effect correlating with participants' behavioral changes in VSTM precision across active and control conditions. Combined, these findings suggest that tDCS over the temporal lobe can modulate the intrinsic functional connectivity between the MTL and visual sensory areas, thereby affecting VSTM precision.
尽管内侧颞叶（MTL）传统上被认为是一个专门负责长期记忆的区域，但最近的神经影像学和颅内记录证据表明，MTL也对视觉短期记忆（VSTM）的某些方面有贡献，比如保留的VSTM内容的质量或精度。本研究旨在通过应用经颅直流电刺激（tDCS）和功能磁共振成像（fMRI）进一步探究MTL在VSTM精度方面的作用。参与者采用左阴极和右阳极电极对双侧颞叶进行1.5毫安的离线tDCS，在20分钟的时间段内，要么施加20分钟（有效），要么在20分钟的窗口内施加0.5分钟（假刺激），采用平衡设计。由于这种双侧刺激方式的电流会穿过中脑结构，先前的行为和模型证据表明，这种tDCS方案可以调节MTL的功能。为了证实这一点并检查其对VSTM的影响，参与者在tDCS后立即完成一项VSTM颜色回忆任务，同时进行20分钟的fMRI扫描和随后7.5分钟的静息态扫描，在此期间他们专注于一个固定十字。行为结果表明，这种tDCS方案降低了VSTM精度，但没有显著影响整体回忆成功率。此外，心理生理交互分析显示，在VSTM任务期间，颞叶上的tDCS调节了海马体与枕叶之间的功能连接，尽管对fMRI的血氧水平依赖（BOLD）活动没有主效应。值得注意的是，在tDCS后15 - 20分钟的静息态fMRI期间也观察到了这种调节，其效应大小与参与者在有效和对照条件下VSTM精度的行为变化相关。综合来看，这些发现表明，颞叶上的tDCS可以调节MTL与视觉感觉区域之间的内在功能连接，从而影响VSTM精度。
