THE RECRUITMENT OF ADULT-BORN GRANULE CELLS AND INTERNEURONS DURING EPISODIC-LIKE MEMORY

Housing rats in an enriched environment (running wheels, toys, huts, hammocks, tunnels etc.) increases the number of adult-born granule cells (abGCs) in the dentate gyrus and is associated with improved performance on difficult episodic-like memory tests (Ventura et al., 2024). Furthermore, enriched animals showed reduced cFos activity throughout the hippocampus. We hypothesised that the augmented population of abGCs in enriched animals recruit interneurons to reduce neuronal activity throughout the hippocampus and facilitate pattern separation in difficult episodic-like memory tests. To address this, we raised male and female Lister Hooded rats in either standard or enriched conditions for three months before behavioural testing using easy and difficult object-context tasks (Dissimilar OC and Similar OC, respectively) for modelling episodic-like memory. Performance in the Dissimilar OC (easy) task was comparable between standard housed and enriched animals (Discrimination index (DI): 0.17 vs 0.38, p=0.073). Whereas enriched animals performed significantly better in the Similar OC (difficult) behavioural task compared to standard housed animals (DI: -0.02 vs 0.21, p=0.026). Additionally, we show that parvalbumin and somatostatin interneurons colocalise with cFos and were active during episodic-like memory tasks (Figure 1). This project investigates how the recruitment of abGCs and interneurons in the hippocampus and lateral entorhinal cortex is altered in enriched animals during difficult episodic-like memory tests. Studying the hippocampal-entorhinal circuitry in this level of detail provides us with a mechanistic insight into memory processing and is fundamental to understand how episodic-memory is disrupted in conditions such as Alzheimer’s disease.