German Centre for Neurodegenerative Diseases (DZNE), Center for Behavioral Brain Sciences (CBBS) & Medical Faculty at Otto von Guericke University, Leipziger Str. 44, 39120, Magdeburg, Germany.
Sci Rep. 2018 Jul 5;8(1):10171. doi: 10.1038/s41598-018-28487-7.
As we move through an environment, the positions of surrounding objects relative to our body constantly change, with some objects even leaving our field of view. As a consequence, maintaining orientation requires spatial updating, the continuous monitoring of self-motion cues to update external locations within an egocentric frame of reference. While previous research using functional magnetic resonance imaging has implicated the precuneus in spatial updating, direct evidence for this claim is missing. To address this important question, we applied theta burst repetitive transcranial magnetic stimulation (rTMS) over the precuneus to induce a "virtual lesion". Following stimulation, participants were tested in a large-scale virtual environment in which they had to use visual self-motion information to keep track of the position of virtual objects. Compared to sham stimulation, rTMS affected working memory traces for object locations. Critically, rTMS further impaired the ability to update these locations whenever participants experienced simulated movement. As this effect could not be explained by working memory deficits alone, we conclude that visual spatial updating relies on the construction of updated representations of egocentric object locations within the precuneus. Together, these findings establish the precuneus as performing key computations for the formation of cognitive maps.
当我们在环境中移动时，周围物体相对于我们身体的位置不断变化，有些物体甚至会离开我们的视野。因此，保持方向感需要空间更新，即持续监测自我运动线索，以便在以自我为中心的参照系中更新外部位置。虽然之前使用功能磁共振成像的研究表明，楔前叶在空间更新中起作用，但这一说法缺乏直接证据。为了解决这个重要的问题，我们应用经颅磁刺激（rTMS）对楔前叶进行θ爆发重复刺激，以产生“虚拟损伤”。刺激后，参与者在一个大型虚拟环境中接受测试，他们必须使用视觉自我运动信息来跟踪虚拟物体的位置。与假刺激相比，rTMS 影响了物体位置的工作记忆痕迹。关键的是，每当参与者经历模拟运动时，rTMS 进一步损害了更新这些位置的能力。由于这种影响不能仅用工作记忆缺陷来解释，我们得出结论，视觉空间更新依赖于在楔前叶内构建自我中心物体位置的更新表示。总之，这些发现确立了楔前叶在形成认知地图方面的关键计算作用。
