C. Elegans Positive Olfactory Associative Memory is a Molecularly Conserved Behavioral Paradigm

While it is thought that short-term memory arises from changes in protein dynamics that increase the strength of synaptic signaling, many of the underlying fundamental molecular mechanisms remain unknown.Our lab developed a Caenorhabditis elegans assay of positive olfactory short-term associative memory (STAM), in which worms learn to associate food with an odor and can remember this association for over 1h. Here we use this massed olfactory associative assay to identify regulators of C. elegans short-term and intermediate-term associative memory (ITAM) processes. We show that there are unique molecular characteristics for different temporal phases of STAM, which include: learning, which is tested immediately after training, short-term memory, tested 30min after training, intermediate-term memory, tested 1h after training, and forgetting, tested 2h after training. We find that, as in higher organisms, C. elegans STAM requires calcium and cAMP signaling, and ITAM requires protein translation. Additionally, we found that STAM and ITAM are distinct from olfactory adaptation, an associative paradigm in which worms learn to disregard an inherently attractive odor after starvation in the presence of that odor. Adaptation mutants show variable responses to short-term associative memory training. Our data distinguish between shorter forms of a positive associative memory in C. elegans that require canonical memory pathways. Study of STAM and ITAM in C. elegans could lead to a more general understanding of the distinctions between these important processes and also to the discovery of novel conserved memory regulators.