HIPPOCAMPAL INDEPENDENT COMPLEX SPATIAL LEARNING IN A LARGE-SCALE MAZE

Prior knowledge networks can accelerate learning and memory consolidation, yet the contribution of the hippocampus across different stages of complex spatial learning remains incompletely understood. Here, we investigated this question using the rat HexMaze, a large-scale (9 × 5 m) naturalistic navigation task in which animals gradually acquire and update a structured spatial knowledge network. Once this cognitive map is established, rats are able to rapidly incorporate new goal locations, providing a framework to dissociate navigation, multi-trial learning, and single-session memory updating. Using hippocampal lesions and pharmacological inactivation, we show that navigation and gradual, multi-trial acquisition of the maze structure are largely hippocampus-independent. In contrast, hippocampal involvement is selectively required for rapid, single-session learning during schema updating. Importantly, once new information was integrated, memory expression and navigation were hippocampus-independent within 48 hours. These findings demonstrate that, in a complex and naturalistic environment, the hippocampus is not required for constructing or maintaining spatial knowledge, but plays a specific role in rapid incorporation of new information into an existing spatial framework.