Coherence among head direction cells before eye opening in rat pups.

Mammalian navigation is thought to depend on an internal map of space consisting of functionally specialized cells in the hippocampus and the surrounding parahippocampal cortices. Basic properties of this map are present when rat pups explore the world outside of their nest for the first time, around postnatal day 16-18 (P16-P18). One of the first functions to be expressed in navigating animals is the directional tuning of the head direction cells.

Identification of dorsal-ventral hippocampal differentiation in neonatal rats.

The adult hippocampal formation (HF) is functionally, connectionally, and transcriptionally differentiated along the dorsal-ventral axis. At birth, the hippocampus appears shortened along its dorsal-ventral axis. We therefore questioned at what postnatal age the differentiated dorsal-ventral hippocampus is present.