The Journal of Neuroscience, April 1, 2002, 22(7):2894-2903
Conservation of Spatial Memory Function in the Pallial Forebrain
of Reptiles and Ray-Finned Fishes
Fernando
Rodríguez,
J. Carlos
López,
J.
Pedro
Vargas,
Yolanda
Gómez,
Cristina
Broglio, and
Cosme
Salas
Laboratorio de Psicobiología, Universidad de Sevilla, 41005 Seville, Spain
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.
Key words:
spatial memory; place learning; pallial forebrain; hippocampus; medial cortex; hippocampal pallium; brain evolution; reptiles; turtles; teleost fish; goldfish; amniotes; ray- finned
fishes
Copyright © 2002 Society for Neuroscience 0270-6474/02/2272894-10$05.00/0
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