title: Conservation of spatial memory function in the pallial forebrain of reptiles and ray-finned fishes.
abstract: The hippocampus of mammals and birds is critical for spatial memory. Neuroanatomical evidence indicates that the medial cortex (MC) of reptiles and the lateral pallium (LP) of ray-finned fishes could be homologous to the hippocampus of mammals and birds. In this work, we studied the effects of lesions to the MC of turtles and to the LP of goldfish in spatial memory. Lesioned animals were trained in place, and cue maze tasks and crucial probe and transfer tests were performed. In experiment 1, MC-lesioned turtles in the place task failed to locate the goal during trials in which new start positions were used, whereas sham animals navigated directly to the goal independently of start location. In contrast, no deficit was observed in cue learning. In experiment 2, LP lesion produced a dramatic impairment in goldfish trained in the place task, whereas medial and dorsal pallium lesions did not decrease accuracy. In addition, none of these pallial lesions produced deficits in cue learning. These results indicate that lesions to the MC of turtles and to the LP of goldfish, like hippocampal lesions in mammals and birds, selectively impair map-like memory representations of the environmental space. Thus, the forebrain structures of reptiles and teleost fish neuroanatomically equivalent to the mammalian and avian hippocampus also share a central role in spatial cognition. Present results suggest that the presence of a hippocampus-dependent spatial memory system is a primitive feature of the vertebrate forebrain that has been conserved through evolution.
authors.affiliation: Laboratorio de Psicobiologia, Universidad de Sevilla, 41005 Seville, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Rodríguez
authors.forename: J Carlos
authors.initials: JC
authors.lastname: López
authors.forename: J Pedro
authors.initials: JP
authors.lastname: Vargas
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Gómez
authors.forename: Cristina
authors.initials: C
authors.lastname: Broglio
authors.forename: Cosme
authors.initials: C
authors.lastname: Salas
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D005075:Biological Evolution; D002540:Cerebral Cortex / Q000502:physiology; D003463:Cues; D006054:Goldfish / Q000502:physiology*; D018782:Maze Learning / Q000502:physiology; D008568:Memory / Q000502:physiology*; D016548:Prosencephalon / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014426:Turtles / Q000502:physiology*