Grid cells without theta oscillations in the entorhinal cortex of bats
Grid cells without theta oscillations in the entorhinal cortex of bats
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DOI：
10.1038/nature10583
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发表时间：
2011-11-03
期刊：
影响因子：
64.8
通讯作者：
Ulanovsky, Nachum
中科院分区：
文献类型：
--
作者：
Yartsev, Michael M.;Witter, Menno P.;Ulanovsky, Nachum
网格细胞提供了空间的神经表示，当动物穿过跨越环境的周期性六角网格的顶点时，网格细胞通过放电来提供空间的神经表示(1)。虽然在大鼠(1-6)中已经详细描述了网格细胞的特征，但什么神经动力学导致网格结构的根本问题仍然没有解决。提出了两类相互竞争的模型：基于吸引子动力学的网络模型(7-9)和振荡干扰模型(10-13)，后者认为单个神经元中躯体和树突的theta带振荡(4-10 Hz)之间的干扰将时间振荡转换为空间周期网格(10-13)。到目前为止，这些模型还不能在实验上分离，因为啮齿动物的网格细胞总是与持续的theta振荡共存(4-6，14)。在这里，我们使用了一个新的动物模型，埃及果蝠(15，16)，驳斥了网格和theta振荡之间的因果联系。根据我们之前对蝙蝠海马体的发现，在没有连续的theta振荡的情况下，空间调谐的位置细胞(17)，我们假设在没有theta振荡的情况下，蝙蝠内侧内嗅觉皮质中的网格细胞也可能存在。事实上，我们发现蝙蝠内侧嗅觉皮质中的网格细胞与啮齿动物的网格细胞有显著的相似之处。值得注意的是，网格的存在没有连续的theta带振荡，也几乎没有网格细胞尖峰的theta调制--这两者都是振荡干扰模型的基本前提。我们的结果为非啮齿动物物种中的网格细胞提供了直接的证据。此外，他们强烈反对一类主要的网格单元计算模型。
Grid cells provide a neural representation of space, by discharging when an animal traverses through the vertices of a periodic hexagonal grid spanning the environment(1). Although grid cells have been characterized in detail in rats(1-6), the fundamental question of what neural dynamics give rise to the grid structure remains unresolved. Two competing classes of models were proposed: network models, based on attractor dynamics(7-9), and oscillatory interference models, which propose that interference between somatic and dendritic theta-band oscillations (4-10 Hz) in single neurons transforms a temporal oscillation into a spatially periodic grid(10-13). So far, these models could not be dissociated experimentally, because rodent grid cells always co-exist with continuous theta oscillations(4-6,14). Here we used a novel animal model, the Egyptian fruit bat(15,16), to refute the proposed causal link between grids and theta oscillations. On the basis of our previous finding from bat hippocampus, of spatially tuned place cells in the absence of continuous theta oscillations(17), we hypothesized that grid cells in bat medial entorhinal cortex might also exist without theta oscillations. Indeed, we found grid cells in bat medial entorhinal cortex that shared remarkable similarities to rodent grid cells. Notably, the grids existed in the absence of continuous theta-band oscillations, and with almost no theta modulation of grid-cell spiking-both of which are essential prerequisites of the oscillatory interference models. Our results provide a direct demonstration of grid cells in a non-rodent species. Furthermore, they strongly argue against a major class of computational models of grid cells.