SCHEMA MEMORY CONSOLIDATION IS HIPPOCAMPAL DEPENDENT

Schemas are cognitive representations that enable the integration of new information into existing knowledge structures. Within the framework of active systems consolidation theory, this updating process depends on coordinated activity between the hippocampus and cortical regions, through which information is transferred from the hippocampus to the cortex. It has been shown, for instance, that pharmacological inhibition of the prefrontal cortex disrupts the recall of recently and remotely consolidated schema-memories. However, whether the hippocampus directly mediates schema-related consolidation during post-encoding sleep remains unresolved, as most studies use multi-day training paradigms that limit direct manipulation of hippocampal sleep activity. Thus, we aimed to determine whether schema memory consolidation depends on the hippocampus by inhibiting hippocampal activity in post-schema-encoding sleep. To address this, a group of male rats received a single infusion of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) into the dorsal hippocampus. Following recovery, rats were trained in an adapted object–place recognition task, which allowed for abstraction of a spatial rule across eight encoding episodes. After encoding, animals received deschloroclozapine to activate the DREADD receptors and inhibit hippocampal activity during post-encoding sleep, while control animals received saline. Schema memory was tested 24 hours later. Our results showed that hippocampal inhibition via DREADDs during post-encoding sleep impaired schema memory formation, confirming that schema consolidation is hippocampus dependent.