Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Rappaport Faculty of Medicine and Research Institute, Technion - Israel Institute of Technology, Haifa, Israel.
Hippocampus. 2021 Jan;31(1):89-101. doi: 10.1002/hipo.23265. Epub 2020 Sep 17.
Place and grid cells in the hippocampal formation are commonly thought to support a unified and coherent cognitive map of space. This mapping mechanism faces a challenge when a navigator is placed in a familiar environment that has been deformed from its original shape. Under such circumstances, many transformations could plausibly serve to map a navigator's familiar cognitive map to the deformed space. Previous empirical results indicate that the firing fields of rodent place and grid cells stretch or compress in a manner that approximately matches the environmental deformation, and human spatial memory exhibits similar distortions. These effects have been interpreted as evidence that reshaping a familiar environment elicits an analogously reshaped cognitive map. However, recent work has suggested an alternative explanation, whereby deformation-induced distortions of the grid code are attributable to a mechanism that dynamically anchors grid fields to the most recently experienced boundary, thus causing history-dependent shifts in grid phase. This interpretation raises the possibility that human spatial memory will exhibit similar history-dependent dynamics. To test this prediction, we taught participants the locations of objects in a virtual environment and then probed their memory for these locations in deformed versions of this environment. Across three experiments with variable access to visual and vestibular cues, we observed the predicted pattern, whereby the remembered locations of objects were shifted from trial to trial depending on the boundary of origin of the participant's movement trajectory. These results provide evidence for a dynamic anchoring mechanism that governs both neuronal firing and spatial memory.
海马结构中的位置和网格细胞通常被认为支持空间的统一和连贯认知图。当导航者处于从原始形状变形的熟悉环境中时，这种映射机制面临挑战。在这种情况下，许多变换都可以合理地将导航者熟悉的认知图映射到变形的空间。先前的经验结果表明，啮齿动物位置和网格细胞的发射场以大致匹配环境变形的方式拉伸或压缩，并且人类空间记忆表现出类似的扭曲。这些效应被解释为证明重塑熟悉的环境会引起类似的重塑认知图的证据。然而，最近的工作提出了另一种解释，即网格码的变形引起的扭曲归因于一种将网格场动态锚定到最近经历的边界的机制，从而导致网格相位的历史依赖性移动。这种解释提出了一种可能性，即人类空间记忆将表现出类似的历史依赖性动态。为了检验这一预测，我们在虚拟环境中教授参与者物体的位置，然后在该环境的变形版本中探测他们对这些位置的记忆。在三个具有可变视觉和前庭线索访问的实验中，我们观察到了预期的模式，即物体的记忆位置根据参与者运动轨迹的起源边界在试验之间发生移动。这些结果为一种动态锚定机制提供了证据，该机制控制着神经元放电和空间记忆。
