Department of Neurology, Neuroscience Center at Dartmouth, Dartmouth Medical School, Dartmouth College, Hanover, New Hampshire 03756, USA.
Hippocampus. 2011 Apr;21(4):347-53. doi: 10.1002/hipo.20789.
The ontogeny of neural substrates underlying episodic memory is not well described. Place cells are a surrogate for episodic memory and are important for spatial navigation in rodents. Although place cells are well described in mature brains, the nature of the maturation processes remains uncertain. We now report on the ontogeny of the place cell system in rats between P22 and P43, a time during which there is rapid improvement in spatial behavior. We found that place cells with adult like firing fields were observed at the earliest ages. However, at this age, adult like place cells were few in number and their place fields were not stable across multiple exposures to the same environment. Independently of confounding factors such as the number of exposures to the environment, the proportion of adult-like place cells, their firing rate, and their stability increased with age and the average spatial signal of all pyramidal cells improved. These findings could account for the poor spatial behavior observed at young ages (P20-P30) and suggests that a small number of adult-like place cells are insufficient to support navigation.
情景记忆的神经基础的个体发生过程描述得还不够清楚。位置细胞是情景记忆的替代物，对啮齿动物的空间导航很重要。尽管成熟大脑中的位置细胞已有很好的描述，但成熟过程的性质仍不确定。我们现在报告了 P22 到 P43 之间大鼠的位置细胞系统的个体发生情况，这是一个空间行为快速改善的时期。我们发现，最早可以观察到具有成人样发射场的位置细胞。然而，在这个年龄，成人样的位置细胞数量很少，它们的位置场在多次暴露于相同环境时不稳定。独立于环境暴露次数等混杂因素，具有成人样的位置细胞的比例、它们的放电率和稳定性随着年龄的增长而增加，所有锥体神经元的平均空间信号也得到改善。这些发现可以解释在年幼时（P20-P30）观察到的较差的空间行为，并表明少量具有成人样的位置细胞不足以支持导航。
