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（GCs）将内嗅皮层连接到海马CA3区，但是它们如何处理空间信息仍然是个谜。为了检查GC在空间编码中的作用，我们测量了在线性带上运行的头固定小鼠中的兴奋性突触后电位（EPSP）和动作电位（AP）。形态学鉴定的GC的细胞内记录表明，大多数细胞都处于活跃状态，但活性水平在很大范围内变化。尽管只有约5％的GC显示了空间调整后的尖峰信号，但约有50％的GC收到了空间调整后的输入信号。因此，GC群体广泛地编码空间信息，但是只有一个子集将此信息中继到CA3网络。傅里叶分析表明，GC接收到了连接格网状的突触输入，提示单个神经元中的代码转换。气相色谱发射与树突的复杂性和固有的兴奋性有关，但与外部的兴奋性输入或树突状电缆的性质无关。因此，功能成熟可以控制输入输出转换和空间代码转换。