The use of the Emotional-Object Recognition as an assay to assess learning and memory associated to an aversive stimulus in rodents

Abstract

Background: Emotionally salient experiences induce the formation of explicit memory traces, besides eliciting automatic or implicit emotional memory in rodents. This study aims at investigating the implementation of a novel task for studying the formation of limbic memory engrams as a result of the acquisition- and retrieval- of fear-conditioning - biased declarative memory traces, measured by animal discrimination of an "emotional-object". Moreover, by using this new method we investigated the potential interactions between stimulation of cannabinoid transmission and integration of emotional information and cognitive functioning.

New method: The Emotional-Object Recognition task is composed of 3 following sessions: habituation; cued fear-conditioned learning; emotional recognition. Rats are exposed to Context "B chamber" for habituation and cued fear-conditioning, and tested in Context "A chamber" for emotional-object recognition.

Results: Cued fear-conditioning induces a reduction in emotional-object exploration time during the Emotional-Object Recognition task in controls. The activation of cannabinoid signalling impairs limbic memory formation, with respect to vehicle.

Comparison to existing methods: The Emotional-Object Recognition test overcomes several limitations of commonly employed methods that explore declarative-, spatial memory and fear-conditioning in a non-integrated manner. It allows the assessment of unbiased cognitive indicators of emotional learning and memory.

Conclusions: The Emotional-Object Recognition task is a valuable tool for investigating whether, and at what extent, specific drugs or pathological conditions that interfere with the individual affective/emotional homeostasis, can modulate the formation of emotionally salient explicit memory traces, thus jeopardizing control and regulation of animal behavioural strategy.

Keywords: CB1 receptor; Explicit emotional memory; Limbic memory engrams; Object discrimination.