Spying on an ancestral brain: activation of a primitive hippocampus in a spatial orientation task.

DANERI, M. FLORENCIA; MUZIO, RUBEN N.

Buenos Aires

Simposio; Frontiers in Bioscience 4 Symposium; 2023

Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA), partner of the Max Planck Society in Argentina.

We are interested in the evolution of neural mechanisms that rule spatial navigation. Spatial orientation is a skill well conserved between vertebrates, suggesting its importance for survival. Looking for learning patterns potentially present in a common ancestor we use the terrestrial toad, Rhinella arenarum, as a model of ancient vertebrate. Amphibians have a homologous area to the hippocampal formation (brain structure involved in spatial learning) called medial pallium, which functions are not yet fully described. We trained toads in a water-finding orientation task using extra maze visual cues and then brains were analyzed using the c-Fos immunohistochemistry technique. Expression of c-Fos is an indirect marker of neuronal activity because it is often expressed when neurons fire action potentials. c-Fos is an immediate early gene (IEG) that codes for a transcription factor that is thought to mediate long-term changes in neural functioning. Thus, c-Fos staining in a neuron indicates recent activity and it is believed that increased c-Fos expression is induced by learning. Our results revealed increased c-Fos + neurons in the medial pallium region, suggesting that this structure is involved in spatial navigation strategies in amphibians. Hippocampus and medial pallium seem to be partially functional equivalents, telling us that this ability is evolutionary conserved.