The hippocampal formation located in the medial temporal lobe of the brain has been studied extensively for several decades, both in in vitro slice preparations and in vivo living animals. Recent advancements in large-scale recording techniques, such as multisite silicon probes and tetrodes, enable us to examine the detailed characteristics of temporal spiking patterns of tens or hundreds of neurons in the hippocampal circuit. Here, we introduce how such tools contribute to our understanding of the hippocampal network dynamics and review several hippocampal functions for information processing in the brain, including pattern separation and completion, spatial representation, and encoding of positive and negative valence.