title: The ventral hippocampus is necessary for expressing a spatial memory.
abstract: Current views posit the dorsal hippocampus (DHipp) as contributing to spatial memory processes. Conversely, the ventral hippocampus (VHipp) modulates stress, emotions and affects. Arguments supporting this segregation include differences in (i) connectivity: the DHipp is connected with the entorhinal cortex which receives visuospatial neocortical inputs; the VHipp is connected with both the amygdala and hypothalamus, (ii) electrophysiological characteristics: there is a larger proportion of place cells in the DHipp than in the VHipp, and an increasing dorsoventral gradient in the size of place fields, suggesting less refined spatial coding in the VHipp, and (iii) consequences of lesions: spatial memory is altered after DHipp lesions, less dramatically, sometimes not, after VHipp lesions. Using reversible inactivation, we report in rats, that lidocaine infusions into the DHipp or VHipp right before a probe trial impair retrieval performance in a water-maze task. This impairment was found at two post-acquisition delays compatible with recent memory (1 and 5 days). Pre-training blockade of the VHipp did not prevent task acquisition and drug-free retrieval, on the contrary to pre-training blockade of DHipp, which altered performance in a subsequent drug-free probe trial. Complementary experiments excluded possible locomotor, sensorimotor, motivational or anxiety-related biases from data interpretation. Our conclusion is that a spatial memory can be acquired with the DHipp, less efficiently with the VHipp, and that the retrieval of such a memory and/or the expression of its representation engages the dorsoventral axis of the hippocampus when the task has been learnt with an entirely functional hippocampus.
authors.affiliation: Laboratoire d'Imagerie et de Neurosciences Cognitives, UMR 7237, Université de Strasbourg, CNRS, IFR 37 des Neurosciences, GDR CNRS 2905 Neuromem, 12 rue Goethe, 67000 Strasbourg, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Loureiro
authors.forename: Lucas
authors.initials: L
authors.lastname: Lecourtier
authors.forename: Michel
authors.initials: M
authors.lastname: Engeln
authors.forename: Joëlle
authors.initials: J
authors.lastname: Lopez
authors.forename: Brigitte
authors.initials: B
authors.lastname: Cosquer
authors.forename: Karin
authors.initials: K
authors.lastname: Geiger
authors.forename: Christian
authors.initials: C
authors.lastname: Kelche
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Cassel
authors.forename: Anne
authors.initials: A
authors.lastname: Pereira de Vasconcelos
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D013028:Space Perception / Q000187:drug effects / Q000502:physiology*
chemical_list: D008012:Lidocaine