Mehta Mayank R
Department of Physics & Astronomy, UCLA, Keck Center for Neurophysics, UCLA.
Department of Neurology, UCLA.
Hippocampus. 2015 Jun;25(6):756-62. doi: 10.1002/hipo.22472.
The entorhinal-hippocampal circuit is crucial for several forms of learning and memory, especially sequence learning, including spatial navigation. The challenge is to understand the underlying mechanisms. Pioneering discoveries of spatial selectivity in this circuit, i.e. place cells and grid cells, provided a major step forward in tackling this challenge. Considerable research has also shown that sequence learning relies on synaptic plasticity, especially the Hebbian or the NMDAR-dependent synaptic plasticity. This raises several questions: Are spatial maps plastic? If so, what is the contribution of Hebbian plasticity to spatial map plasticity? How does the spatial map plasticity contribute to sequence learning? A combination of computational and experimental studies has shown that NMDAR-mediated plasticity and theta rhythm can have specific effects on the formation and experiential modification of spatial maps to facilitate predictive coding. Advances in transgenic techniques have provided further support for these mechanisms. Although many exciting challenges remain, these findings have brought us closer to solving the puzzle of how the hippocampal system contributes to spatial memory, and point to a way forward.
内嗅皮层-海马回路对于多种形式的学习和记忆至关重要，尤其是序列学习，包括空间导航。挑战在于理解其潜在机制。该回路中空间选择性的开创性发现，即位置细胞和网格细胞，为应对这一挑战向前迈出了重要一步。大量研究还表明，序列学习依赖于突触可塑性，尤其是赫布型或NMDAR依赖性突触可塑性。这引发了几个问题：空间图谱是否具有可塑性？如果是，赫布型可塑性对空间图谱可塑性有何贡献？空间图谱可塑性如何促进序列学习？计算和实验研究相结合表明，NMDAR介导的可塑性和theta节律可对空间图谱的形成和经验性修饰产生特定影响，以促进预测编码。转基因技术的进展为这些机制提供了进一步支持。尽管仍有许多令人兴奋的挑战，但这些发现使我们更接近解决海马系统如何促成空间记忆这一谜题，并指明了前进的方向。
