Noradrenaline Effects on the Systems Consolidation of Memory

Abstract

The stress hormones noradrenaline and corticosterone are assumed to have opposite effects on memory generalization versus accuracy. While the effect of corticosterone on promoting memory generalisation resembles to what normally occurs over the course of systems consolidation of memory, it remains unknown how noradrenaline establishes its effect on promoting memory accuracy. In this project, we investigated whether increased noradrenaline levels during memory consolidation affect the systems consolidation process at the level of engram neurons and thereby enhance the accuracy of memories during remote retention testing. We used a transgenic mouse model and developed a new behavioural task to assess memory accuracy in mice. This mouse model allowed us to label active neurons during training in vivo and immunostaining of brain material acquired right after testing labeled neurons activated at the retention test. Here we show that post-training administration of yohimbine (a noradrenergic stimulant) enhanced memory accuracy during testing 14 days later and this was associated with enhanced hippocampal activity and diminished correlated activity of the prefrontal cortex and CA3 at the time of testing. These findings provide further insight into the mechanism by which