title: Delay-dependent involvement of the rat entorhinal cortex in habituation to a novel environment.
abstract: Evidence has accumulated that the entorhinal cortex (EC) is involved in memory operations underlying formation of a long-term memory. Because entorhinal-lesioned rats are impaired for long delays in delayed matching and non-matching to sample tasks, it has been proposed that EC contributes to the maintenance of information in short-term memory. In the present study, we asked whether such a time-limited role applies also when learning complex spatial information in a novel environment. We therefore examined the effects of EC lesions on habituation in an object exploration task in which a delay of either 4min or 10min is imposed between successive sessions. EC-lesioned rats exhibited a deficit in habituation at 10min but not 4min delays. Following habituation, reactions to spatial change (object configuration) and non-spatial change (novel object) were also examined. EC-lesioned rats were impaired in detecting the spatial change but were able to detect a non-spatial change, irrespective of the delay. Overall, the results suggest that EC is involved in maintaining a large amount of novel, multidimensional information in short-term memory therefore enabling formation of long-term memory. Switching to a novelty detection mode would then allow the animal to rapidly adapt to environmental changes. In this mode, EC would preferentially process spatial information rather than non-spatial information.
authors.affiliation: Laboratory of Neurobiology and Cognition, UMR 6155 Aix Marseille Université, CNRS, Pôle 3C, 3 Place Victor Hugo, 13331 Marseille Cedex 3, France.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Van Cauter
authors.forename: Bruno
authors.initials: B
authors.lastname: Poucet
authors.forename: Etienne
authors.initials: E
authors.lastname: Save
mesh_terms: D000818:Animals; D018728:Entorhinal Cortex / Q000502:physiology*; D004777:Environment; D005106:Exploratory Behavior / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D013028:Space Perception / Q000502:physiology*; D013997:Time Factors