A novel behavioral paradigm to model hypermemory-like features in rats

Researchers have created a new behavioral approach to simulate hypermemory-like characteristics in rats. This method focuses on enhancing and maintaining memory, a crucial aspect of everyday life and personal identity, which can become dysregulated and lead to mental health issues when amplified. Traditional rodent tests primarily examine memory impairments, but this innovative approach aims to replicate the abnormal strengthening and persistence of specific memories, a phenomenon linked to hyperfunctional episodic memory.

To achieve this, the researchers modified object recognition (OR) and object location (OL) tasks. Initially, the rats were exposed to two identical objects scented with cinnamon. For the subsequent 6 hours, they underwent 12 brief re-exposures in their home cages, either to the cinnamon odor or an odorless stimulus. This repeated activation of the memory trace facilitated its hyperconsolidation without reintroducing the original context or objects.

A day later, memory was evaluated in an odor-free setting. The results revealed that odor re-exposure specifically bolstered OL memory in both male and female rats, while OR memory was left unaltered.

Interestingly, this procedure did not affect the overall object exploration or overall movement of the rats. Moreover, the heightened spatial memory was correlated with increased c-Fos expression in the ventral hippocampus, a brain region involved in memory processing. This protocol captures key components of hypermemory, such as continuous memory reactivation and rumination, which contribute to the excessive strengthening and persistence of certain memories.

As a result, this straightforward and reproducible paradigm offers a fresh and valuable tool for studying the behavioral and neurobiological mechanisms responsible for memory hyperconsolidation and its potential role in maladaptive memory persistence.