Abstract
A painful event establishes two opponent memories: cues that are associated with pain onset are remembered negatively, whereas cues that coincide with the relief at pain offset acquire positive valence. Such punishment- versus relief-memories are conserved across species, including humans, and the balance between them is critical for adaptive behaviour with respect to pain and trauma. In the fruit fly, Drosophila melanogaster as a study case, we found that both punishment- and relief-memories display natural variation across wild-derived inbred strains, but they do not covary, suggesting a considerable level of dissociation in their genetic effectors. This provokes the question whether there may be heritable inter-individual differences in the balance between these opponent memories in man, with potential psycho-clinical implications.
Highlights
A painful, traumatic event leaves behind two opponent memories [1]: Cues that come before or during pain later on induce avoidance, potentiate fear behaviour and are verbally reported to have negative valence
Do these memories display natural genetic variation? Do they covary? Can the natural variation, if any, be used to identify candidate genes that distinguish between them or keep them in balance? We turned to the fruit fly as a case to tackle these questions for the first time
We found that both punishment- and relief-memories vary across a comprehensive set of wild-derived inbred fly strains, but do so independently from each other, suggesting significant dissociation in their genetic bases
Summary
A painful, traumatic event leaves behind two opponent memories [1]: Cues that come before or during pain later on induce avoidance (in fruit flies: [2,3,4,5,6,7,8]), potentiate fear behaviour (in rats and man: [9,10]) and are verbally reported to have negative valence (in man: [9]). We found that both punishment- and relief-memories vary across a comprehensive set of wild-derived inbred fly strains, but do so independently from each other, suggesting significant dissociation in their genetic bases. As a first step towards a systematic comparison of punishment- versus relief-memory at the level of the genetic effectors, we ran association analyses between the memory scores and the available transcriptomic/genomic data [13,14] of the inbred strains, yielding candidate genes.
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