LaChance Patrick A, Winter Shawn S, Taube Jeffrey S
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, NH 03755, USA; Department of Psychological and Brain Sciences, Boston University, Boston, MA 02215, USA.
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, NH 03755, USA.
Curr Biol. 2025 May 19;35(10):2379-2390.e5. doi: 10.1016/j.cub.2025.04.036. Epub 2025 May 5.
Navigation is commonly associated with two-dimensional (2D) representations of space. Recordings from place and grid cells in the rodent and bat brain have largely upheld this association. Recent studies have investigated how these 2D representations might extend into the three-dimensional (3D) world. One unexplored question is whether grid cells represent vertically separated horizontal surfaces as a single 3D space or distinct planar environments. To address this issue, we recorded grid cells as rats foraged in both an open-field environment and one with a transparent floor suspended directly above the open-field environment. Rats either actively locomoted up a ramp to the elevated environment, or they were passively moved between the two environments, to test how differences in path integration may affect grid cell firing. We found that grid cell firing patterns in the elevated environment were translated (but not rotated) relative to those in the floor environment and were consistent across active and passive sessions. The translation of the grid pattern on the elevated surface was consistent among co-recorded grid cells but differed between animals and between different groups of grid cells recorded from the same animal. Non-grid spatially modulated cells also rearranged their location preferences between the two surfaces. Overall, we did not observe any evidence that the two surfaces were represented with a single 3D representation but instead were treated as two distinct surfaces connected by a common orientation signal. These findings suggest that grid cell representations on visually distinct, vertically displaced horizontal surfaces are planar rather than volumetric.
导航通常与空间的二维（2D）表示相关联。对啮齿动物和蝙蝠大脑中位置细胞和网格细胞的记录在很大程度上支持了这种关联。最近的研究探讨了这些二维表示如何扩展到三维（3D）世界。一个未被探索的问题是，网格细胞是将垂直分隔的水平表面表示为一个单一的三维空间，还是不同的平面环境。为了解决这个问题，我们在大鼠于旷场环境以及在直接悬浮于旷场环境上方的透明地板环境中觅食时记录网格细胞。大鼠要么主动沿着斜坡爬上高处环境，要么在两种环境之间被动移动，以测试路径积分的差异如何影响网格细胞的放电。我们发现，高处环境中的网格细胞放电模式相对于地面环境中的放电模式发生了平移（但没有旋转），并且在主动和被动实验中都是一致的。高处表面上网格模式的平移在共同记录的网格细胞之间是一致的，但在不同动物之间以及从同一动物记录的不同组网格细胞之间存在差异。非网格空间调制细胞在两个表面之间也重新排列了它们的位置偏好。总体而言，我们没有观察到任何证据表明这两个表面以单一的三维表示形式呈现，而是被视为由共同方向信号连接的两个不同表面。这些发现表明，在视觉上不同、垂直位移的水平表面上的网格细胞表示是平面的而非立体的。
