The amphibian medial pallium as a model of an ancestral hippocampus?

DANERI, M. F. & MUZIO, R. N.

Mar del Plata, Argentina.

Congreso; XXXII Congress of the Argentinean Society for Research in Neuroscience.; 2017

Argentinean Society for Research in Neuroscience.

We are interested in the evolution of neural mechanisms that rule spatial learning.Our group is looking for learning patterns potentially present in a common ancestor to several vertebrates using as model the terrestrial toad, Rhinella arenarum. It is known that mammalian hippocampus is a critical brain structure involved in spatial learning and amphibians have a homologous area to this hippocampal formation,the medial pallium. The analysis of how involved this structure is in spatial orientation tasks will help us to infer potential ancestral spatial abilities and its neural basis. We conducted medial pallium lesion studies with toads daily trained in a plus maze for the acquisition of two basic spatial orientation strategies: a visual cue guided response and a turn response toreach a goal. In addition, spatial learning and memory related morphological changes in the argyrophilic nucleolar organizer region (AgNOR) of medial pallium neurons were quantitatively evaluated by means of AgNOR neurohistochemical stain in other set of experiments. Altogether, our results suggest that medial pallium is involved in basic spatial orientation strategies in amphibians, supporting thus the idea that hippocampus and medial pallium are partially functional equivalents. Furthermore, these results telling us that this ability is evolutionary conserved.