Neural correlates of place learning in the cane toad, Rhinella marina

Abstract

Learning locations by integrating external reference points, or place learning, is a form of navigation strongly associated with the mammalian hippocampus and its homologs in other vertebrates. In contrast, cue learning relies on individual environmental features and can occur independently of the hippocampus. Despite growing interest in amphibian spatial cognition and association of spatial functions with the medial pallium brain region, how amphibian brains support different spatial learning strategies remains unknown. We designed a four-arm maze to test place, cue, and turn-direction learning in the cane toad (Rhinella marina), and paired maze trials with visualization of brain activity through pS6 immunohistochemistry. Toads improved performance over time only in the place task but exhibited consistently faster exit times in the cue task. Place task toads displayed elevated brain activity only in the dorsal and lateral palliums. These observations demonstrate that amphibians can acquire spatial navigation strategies through distinct behavioral paradigms and reveal the diverse pallial contributions underlying vertebrate spatial cognition.