Stewart Sarah, Jeewajee Ali, Wills Thomas J, Burgess Neil, Lever Colin
Institute of Psychological Sciences, University of Leeds, , Leeds LS2 9JT, UK.
Philos Trans R Soc Lond B Biol Sci. 2013 Dec 23;369(1635):20120514. doi: 10.1098/rstb.2012.0514. Print 2014 Feb 5.
The spatial mapping function of the hippocampal formation is likely derived from two sets of information: one based on the external environment and the other based on self-motion. Here, we further characterize 'boundary vector cells' (BVCs) in the rat subiculum, which code space relative to one type of cue in the external environment: boundaries. We find that the majority of cells with fields near the perimeter of a walled environment exhibit an additional firing field when an upright barrier is inserted into the walled environment in a manner predicted by the BVC model. We use this property of field repetition as a heuristic measure to define BVCs, and characterize their spatial and temporal properties. In further tests, we find that subicular BVCs typically treat drop edges similarly to walls, including exhibiting field repetition when additional drop-type boundaries are added to the testing environment. In other words, BVCs treat both kinds of edge as environmental boundaries, despite their dissimilar sensory properties. Finally, we also report the existence of 'boundary-off cells', a new class of boundary-coding cells. These cells fire everywhere except where a given BVC might fire.
一组基于外部环境，另一组基于自身运动。在此，我们进一步刻画大鼠下托中的“边界向量细胞”（BVCs），这些细胞相对于外部环境中的一种线索——边界来编码空间。我们发现，当一个直立屏障按照BVC模型预测的方式插入有围墙的环境中时，大多数在有围墙环境周边附近有活动域的细胞会表现出一个额外的放电域。我们利用这种域重复特性作为一种启发式测量方法来定义BVCs，并刻画它们的空间和时间特性。在进一步的测试中，我们发现下托BVCs通常对落差边缘的处理方式与墙壁类似，包括当向测试环境中添加额外的落差型边界时会表现出域重复。换句话说，BVCs将这两种边缘都视为环境边界，尽管它们的感觉特性不同。最后，我们还报告了“边界关闭细胞”的存在，这是一类新的边界编码细胞。这些细胞在除了给定BVC可能放电的位置之外的所有地方都放电。
