title: Maturational dynamics of hippocampal place cells in immature rats.
abstract: The ontogeny of neural substrates underlying episodic memory is not well described. Place cells are a surrogate for episodic memory and are important for spatial navigation in rodents. Although place cells are well described in mature brains, the nature of the maturation processes remains uncertain. We now report on the ontogeny of the place cell system in rats between P22 and P43, a time during which there is rapid improvement in spatial behavior. We found that place cells with adult like firing fields were observed at the earliest ages. However, at this age, adult like place cells were few in number and their place fields were not stable across multiple exposures to the same environment. Independently of confounding factors such as the number of exposures to the environment, the proportion of adult-like place cells, their firing rate, and their stability increased with age and the average spatial signal of all pyramidal cells improved. These findings could account for the poor spatial behavior observed at young ages (P20-P30) and suggests that a small number of adult-like place cells are insufficient to support navigation.
authors.affiliation: Department of Neurology, Neuroscience Center at Dartmouth, Dartmouth Medical School, Dartmouth College, Hanover, New Hampshire 03756, USA. rscott@ich.ucl.ac.uk
authors.forename: Rod C
authors.initials: RC
authors.lastname: Scott
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Richard
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Holmes
authors.forename: Pierre-Pascal
authors.initials: PP
authors.lastname: Lenck-Santini
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000375:Aging / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D008568:Memory / Q000502:physiology; D017966:Pyramidal Cells / Q000254:growth & development*; D051381:Rats; D013028:Space Perception / Q000502:physiology; D013037:Spatial Behavior / Q000502:physiology*; D013223:Statistics as Topic; D013997:Time Factors