Abstract
Unraveling the molecular mechanisms underlying memory formation in insects and a comparison with those of mammals will contribute to a further understanding of the evolution of higher-brain functions. As it is for mammals, insect memory can be divided into at least two distinct phases: protein-independent short-term memory and protein-dependent long-term memory (LTM). We have been investigating the signaling pathway of LTM formation by behavioral-pharmacological experiments using the cricket Gryllus bimaculatus, whose olfactory learning and memory abilities are among the highest in insect species. Our studies revealed that the NO-cGMP signaling pathway, CaMKII and PKA play crucial roles in LTM formation in crickets. These LTM formation signaling pathways in crickets share a number of attributes with those of mammals, and thus we conclude that insects, with relatively simple brain structures and neural circuitry, will also be beneficial in exploratory experiments to predict the molecular mechanisms underlying memory formation in mammals.
Highlights
Brain structures and neural circuitry of insects are relatively simple, and they are useful for exploratory experiments to predict the molecular mechanisms underlying memory formation in mammals
We investigated whether cAMP signaling is necessary for long-term memory (LTM) formation in the cricket (Matsumoto et al, 2006, 2009)
The results of our experiments using ‘LTM-inhibiting’ drugs showed that cAMP signaling is necessary for LTM formation in the cricket, but is it sufficient for LTM formation? To address this issue, we investigated whether forced LTM formation occurs by upregulating the cAMP signaling pathway during single-trial conditioning, which does not form LTM
Summary
Brain structures and neural circuitry of insects are relatively simple, and they are useful for exploratory experiments to predict the molecular mechanisms underlying memory formation in mammals. Memory in insects as well as that in vertebrates is a dynamic process organized in two main types: short-term memory (STM) and long-term memory (LTM) The former is defined as protein synthesis-independent memory, and the latter is defined as protein synthesis-dependent memory. Crickets provide several advantages to investigate memoryrelated molecules They demonstrate remarkable ability of olfactory learning and memory, including that requires cognitive functions. They exhibit robust olfactory memory maintained throughout their lifetime (Matsumoto and Mizunami, 2002a), contextual learning (Matsumoto and Mizunami, 2004), high capacity of memory storage (Matsumoto and Mizunami, 2006), second-order conditioning (Mizunami et al, 2009), and sensory preconditioning (Matsumoto et al, 2013a). There has been a good accumulation of knowledge that bridges between the nervous system and behavior of crickets gained by extensive neuroethological studies in crickets (Stevenson and Schildberger, 2013; Hedwig, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
