Zhang Xiaomin, Jonas Peter
IST Austria (Institute of Science and Technology Austria), Cellular Neuroscience, Am Campus 1 A-3400 Klosterneuburg, Austria.
J Life Sci (Westlake Village). 2020 Dec;2(4):19-24.
The hippocampus is the key site for learning and memory and for processing of spatial information in the brain. It is divided into three main subregions: the dentate gyrus (DG), the CA3 area, and the CA1 region, which are linearly interconnected to form a so-called trisynaptic circuit. Thus, the DG sits in a strategic position to gate the flow of information from the neocortex into the hippocampal network. The granule cells (GCs), the main cell type in the DG, receive 'where' and 'what' information from the medial and lateral entorhinal cortex, respectively. How they process this mixed information remains enigmatic. By characterizing the spatial information encoded by the excitatory postsynaptic potentials (EPSPs) in GCs, we demonstrated that the majority of GCs received spatially tuned synaptic input. However, only a minority of GCs successfully converted spatially tuned input to spatially tuned output. Furthermore, we found that mature GCs were highly heterogeneous in terms of their dendritic morphology and intrinsic excitability, which contributes to the sparse and heterogeneous firing of GCs. Finally, we discuss the possible origin of this neural heterogeneity and its potential role in enlarging the computational power of the DG, facilitating pattern separation in this network.
海马体是大脑中学习、记忆以及处理空间信息的关键部位。它主要分为三个子区域：齿状回（DG）、CA3区和CA1区，这些区域线性互连形成所谓的三突触回路。因此，齿状回处于一个关键位置，可控制信息从新皮层流入海马体网络。颗粒细胞（GCs）是齿状回中的主要细胞类型，分别从中内嗅皮层和侧内嗅皮层接收“位置”和“事物”信息。它们如何处理这些混合信息仍然是个谜。通过对颗粒细胞中兴奋性突触后电位（EPSPs）编码的空间信息进行表征，我们证明了大多数颗粒细胞接收到空间调谐的突触输入。然而，只有少数颗粒细胞成功地将空间调谐输入转换为空间调谐输出。此外，我们发现成熟的颗粒细胞在树突形态和内在兴奋性方面高度异质，这导致了颗粒细胞的稀疏和异质放电。最后，我们讨论了这种神经异质性的可能起源及其在扩大齿状回计算能力、促进该网络模式分离中的潜在作用。
