Learning and Memory

Abstract

Crickets have excellent capabilities for olfactory and visual learning and thus are useful organisms in which to study the mechanisms of learning and memory. Our studies on crickets have revealed detailed information about signaling cascades underlying long-term memory (LTM) formation, namely, that the serial activation of the NO-cGMP system, cyclic nucleotide-gated (CNG) channel, the calcium/calmodulin system, and cAMP-protein kinase A (PKA) underlies LTM formation. Our studies also suggest that octopaminergic (OA-ergic) and dopaminergic (DA-ergic) neurons convey information about appetitive or aversive unconditioned stimuli (US), respectively, in conditioning of odors, visual patterns, and color cues. Our studies also suggest that activation of OA-ergic and DA-ergic neurons is needed for retrieval of appetitive and aversive memory, respectively, in olfactory learning and visual learning. Many of these findings differ from those reported for the fruit fly Drosophila, suggesting unexpected diversity in the mechanisms of learning and memory in different species of insects. Studies of the functional significance and underlying evolutionary history of such diversity should emerge as important areas of research. Recently, new techniques such as RNA interference and transgenesis have been successfully applied to crickets, which should help deepen the study of the cellular and molecular mechanisms of learning and memory in crickets.