Hippocampal Network Dynamics during Rearing Episodes

Abstract

Summary: Animals build a model of their surroundings on the basis of information gathered during exploration. Rearing on the hindlimbs changes the vantage point of the animal, increasing the sampled area of the environment. This environmental knowledge is suggested to be integrated into a cognitive map stored by the hippocampus. Previous studies have found that damage to the hippocampus impairs rearing. Here, we characterize the operational state of the hippocampus during rearing episodes. We observe an increase of theta frequency paralleled by a sink in the dentate gyrus and a prominent theta-modulated fast gamma transient in the middle molecular layer. On the descending phase of rearing, a decrease of theta power is detected. Place cells stop firing during rearing, while a different subset of putative pyramidal cells is activated. Our results suggest that the hippocampus switches to a different operational state during rearing, possibly to update spatial representation with information from distant sources. : By combining high speed tracking in three dimensions and multichannel recording, Barth et al. characterize the network dynamics in the hippocampus during rearing episodes. They observe augmented impulse flow through the medial perforant pathway accompanied by the activation of certain principal cells and decrease of place cell activity. Keywords: theta rhythm, gamma oscillation, cross-frequency coupling, place cell, motion capture, silicone probe, independent component analysis, CA1, dentate gyrus, navigation