Dentate gyrus granule cells (GCs) connect the entorhinal cortex to the hippocampal CA3 region, but how they process spatial information remains enigmatic. To examine the role of GCs in spatial coding, we measured excitatory postsynaptic potentials (EPSPs) and action potentials (APs) in head-fixed mice running on a linear belt. Intracellular recording from morphologically identified GCs revealed that most cells were active, but activity level varied over a wide range. Whereas only ∼5% of GCs showed spatially tuned spiking, ∼50% received spatially tuned input. Thus, the GC population broadly encodes spatial information, but only a subset relays this information to the CA3 network. Fourier analysis indicated that GCs received conjunctive place-grid-like synaptic input, suggesting code conversion in single neurons. GC firing was correlated with dendritic complexity and intrinsic excitability, but not extrinsic excitatory input or dendritic cable properties. Thus, functional maturation may control input-output transformation and spatial code conversion.

齿状回颗粒细胞 (GC) 将内嗅皮层与海马 CA3 区域连接起来，但它们如何处理空间信息仍然是个谜。为了研究 GC 在空间编码中的作用，我们测量了在线性带上跑步的头部固定小鼠的兴奋性突触后电位 (EPSP) 和动作电位 (AP)。形态学鉴定的 GC 的细胞内记录显示，大多数细胞都是活跃的，但活动水平变化范围很大。虽然只有 ∼5% 的 GC 显示出空间调整的尖峰，但 ∼50% 的 GC 接收了空间调整的输入。因此，GC 群体广泛地编码空间信息，但只有一个子集将此信息中继到 CA3 网络。傅里叶分析表明，GC 接收了联合位置网格状突触输入，表明单个神经元中存在代码转换。 GC 放电与树突复杂性和内在兴奋性相关，但与外在兴奋性输入或树突电缆特性无关。因此，功能成熟可以控制输入输出变换和空间代码转换。