Phase precessing place cells encode spatial information on fine timescales via the timing of their spikes. This phase code has been extensively studied on linear tracks and for short runs in the open field. However, less is known about the phase code on unconstrained trajectories lasting tens of minutes, typical of open field foraging. In previous work (Monsalve-Mercado and Leibold, Physical Review Letters, 119, 38101 (2017)), an analytic expression was derived for the spike-time cross-correlation between phase precessing place cells during natural foraging in the open field. This expression makes two predictions on how this phase code differs from the linear track case: cross-correlations are symmetric with respect to time, and they represent the distance between pairs of place fields in that the theta-filtered cross-correlations around zero time lag are positive for cells with nearby fields while they are negative for those with fields further apart. Here we analyze several available open field recordings and show that these predictions hold for pairs of CA1 place cells. We also show that the relationship remains during remapping in CA1, and it is also present in place cells in area CA3. For CA1 place cells of Fmr1-null mice, which exhibit normal place fields but somewhat weaker temporal coordination with respect to theta compared to wild type, the cross-correlations still remain symmetric but the relationship to place field overlap is largely lost. The relationship discussed here describes how spatial information is communicated by place cells to downstream areas in a finer theta-timescale, relevant for learning and memory formation in behavioral tasks lasting tens of minutes in the open field.

中文翻译：

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在开阔的野外觅食过程中，海马尖峰时间相关性和地点场重叠。

相位进动位置细胞通过它们的尖峰时间在精细的时间尺度上编码空间信息。该相位码已在线性轨道上和在空旷的短程中进行了广泛的研究。然而，对于持续数十分钟的无约束轨迹上的相位代码知之甚少，这是典型的露天觅食。在之前的工作中（Monsalve-Mercado 和 Leibold，Physical Review Letters, 119, 38101 (2017)），推导出了露天自然觅食期间相位进动位置细胞之间尖峰时间互相关的分析表达式。这个表达式对这个相位码与线性轨道情况的不同做出了两个预测：互相关关于时间是对称的，它们代表位置场对之间的距离，因为零时滞附近的θ滤波互相关对于具有附近场的单元格是正的，而对于那些场相距较远的单元格则是负值。在这里，我们分析了几个可用的开放场记录，并表明这些预测适用于成对的 CA1 位置细胞。我们还表明这种关系在 CA1 中的重新映射期间仍然存在，并且它也存在于 CA3 区域的单元格中。对于 Fmr1-null 小鼠的 CA1 位置细胞，与野生型相比，它们表现出正常的位置场，但相对于 theta 的时间协调性稍弱，互相关仍然保持对称，但与位置场重叠的关系在很大程度上丢失了。