在我们走动时，空间信息被大脑海马体中的“地点”细胞编码和处理。这些神经细胞中的每一个当处在它应在的“地点”时，会加快其激发速度，从而使速度编码等同于地点。
海马体地点细胞的激发模式在过去40年里已得到广泛研究，而且人们也提出了一些理论模型来解释神经回路中地点和时间的编码机制。现在，研究人员开发出一种技术，该技术能从实验鼠的地点细胞内来记录编码情况。实验中，研究人员让小鼠处于清醒状态，并让它们走一个虚拟现实迷宫。这一技术使得研究人员有可能来验证这些模型。初步结果表明，地点场存在两个阈下特征参数：一个是膜电位振荡在Theta频率处振幅的增加，另一个是基线膜电位像坡道一样的去极化。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 461, 941-946 (15 October 2009) | doi:10.1038/nature08499
Intracellular dynamics of hippocampal place cells during virtual navigation
Christopher D. Harvey1,2,3, Forrest Collman1,2,3, Daniel A. Dombeck1,2,3 & David W. Tank1,2,3
1 Princeton Neuroscience Institute,
2 Lewis-Sigler Institute for Integrative Genomics,
3 Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
Correspondence to: David W. Tank1,2,3 Correspondence and requests for materials should be addressed to D.W.T.
Hippocampal place cells encode spatial information in rate and temporal codes. To examine the mechanisms underlying hippocampal coding, here we measured the intracellular dynamics of place cells by combining in vivo whole-cell recordings with a virtual-reality system. Head-restrained mice, running on a spherical treadmill, interacted with a computer-generated visual environment to perform spatial behaviours. Robust place-cell activity was present during movement along a virtual linear track. From whole-cell recordings, we identified three subthreshold signatures of place fields: an asymmetric ramp-like depolarization of the baseline membrane potential, an increase in the amplitude of intracellular theta oscillations, and a phase precession of the intracellular theta oscillation relative to the extracellularly recorded theta rhythm. These intracellular dynamics underlie the primary features of place-cell rate and temporal codes. The virtual-reality system developed here will enable new experimental approaches to study the neural circuits underlying navigation.
