Department of Neurobiology, Stanford University School of Medicine, Stanford, CA, USA.
Department of Applied Physics, Stanford University, Stanford, CA, USA.
Nature. 2024 Nov;635(8040):943-950. doi: 10.1038/s41586-024-08034-3. Epub 2024 Oct 9.
Animals must navigate changing environments to find food, shelter or mates. In mammals, grid cells in the medial entorhinal cortex construct a neural spatial map of the external environment. However, how grid cell firing patterns rapidly adapt to novel or changing environmental features on a timescale relevant to behaviour remains unknown. Here, by recording over 15,000 grid cells in mice navigating virtual environments, we tracked the real-time state of the grid cell network. This allowed us to observe and predict how altering environmental features influenced grid cell firing patterns on a nearly instantaneous timescale. We found evidence that visual landmarks provide inputs to fixed points in the grid cell network. This resulted in stable grid cell firing patterns in novel and altered environments after a single exposure. Fixed visual landmark inputs also influenced the grid cell network such that altering landmarks induced distortions in grid cell firing patterns. Such distortions could be predicted by a computational model with a fixed landmark to grid cell network architecture. Finally, a medial entorhinal cortex-dependent task revealed that although grid cell firing patterns are distorted by landmark changes, behaviour can adapt via a downstream region implementing behavioural timescale synaptic plasticity. Overall, our findings reveal how the navigational system of the brain constructs spatial maps that balance rapidity and accuracy. Fixed connections between landmarks and grid cells enable the brain to quickly generate stable spatial maps, essential for navigation in novel or changing environments. Conversely, plasticity in regions downstream from grid cells allows the spatial maps of the brain to more accurately mirror the external spatial environment. More generally, these findings raise the possibility of a broader neural principle: by allocating fixed and plastic connectivity across different networks, the brain can solve problems requiring both rapidity and representational accuracy.
动物必须在不断变化的环境中寻找食物、住所或配偶。在哺乳动物中，内侧缰状回皮层中的网格细胞构建了外部环境的神经空间图。然而，网格细胞的放电模式如何在与行为相关的时间尺度上快速适应新的或变化的环境特征仍然未知。在这里，通过在小鼠导航虚拟环境中记录超过 15000 个网格细胞，我们跟踪了网格细胞网络的实时状态。这使我们能够观察和预测改变环境特征如何在几乎瞬间的时间尺度上影响网格细胞的放电模式。我们有证据表明，视觉地标为网格细胞网络中的固定点提供输入。这导致在单次暴露后，在新的和改变的环境中稳定的网格细胞放电模式。固定的视觉地标输入也会影响网格细胞网络，从而导致地标变化诱导网格细胞放电模式的扭曲。这种扭曲可以通过具有固定地标到网格细胞网络架构的计算模型来预测。最后，一个内侧缰状回皮层依赖的任务表明，尽管网格细胞的放电模式由于地标变化而扭曲，但行为可以通过执行行为时间尺度突触可塑性的下游区域来适应。总的来说，我们的研究结果揭示了大脑的导航系统如何构建平衡速度和准确性的空间地图。地标和网格细胞之间的固定连接使大脑能够快速生成稳定的空间地图，这对于在新的或变化的环境中导航至关重要。相反，网格细胞下游区域的可塑性允许大脑的空间地图更准确地反映外部空间环境。更一般地说，这些发现提出了一个更广泛的神经原则的可能性：通过在不同的网络中分配固定和可塑性的连接，大脑可以解决既需要速度又需要表示准确性的问题。
