Traumatic Conditioning Induces a Combination of Anesthesia Resistant Memory and Protein Synthesis Dependent Long-Term Memory in Adult Drosophila

Abstract

Stressful experiences elicit long-lasting memory trace that often persists for life-time. Though storage of experience dependent memory is key to survival, post-traumatic memories are detrimental to the physical and emotional wellbeing. The generation of any form of long-term memory culminates from synaptic plasticity and potentiation through persistent change in protein synthesis. Drosophila has been a robust model for the study of memory mechanisms; olfactory memory paradigms have been enormously successful in elucidating neuroanatomical, molecular, physiological and signalling pathways underlying the process. Long-term memory (LTM) has been induced by protein synthesis dependent mechanisms followed by a post-learning consolidation process whereas a medium-term anaesthesia resistant memory (ARM) is mediated by the Radish protein in flies. Here we present a novel and simple memory paradigm in adult flies for inducing sustained stress-induced memory paradigm, where a single attractive odorant is associated with an aversive stimulus-copper sulfate, which provides bitter taste as well as sustained malaise due to toxicity. We find that the elicited memory is a combination of ARM and LTM which is dependent on the number of training cycles. The eight-cycle training paradigm leads to robust, CREB and protein synthesis dependent memory persisting for about 7 days. The mushroom body (MB) Kenyon cells neurons as well as the dopaminergic input neurons (PPL1 subset) are involved in the formation of memory mediated by enhanced calcium as well as synaptic elaboration in the {gamma} subset of the MB neurons.