Molecular Mechanisms of Memory Storage in Aplysia

Center for Neurobiology and Behavior, College of Physicians and Surgeons of Columbia University, 1051 Riverside Drive, New York, NY 10032, USA.
Biological Bulletin (Impact Factor: 1.64). 07/2006; 210(3):174-91. DOI: 10.2307/4134556
Source: PubMed


Cellular studies of implicit and explicit memory suggest that experience-dependent modulation of synaptic strength and structure is a fundamental mechanism by which these memories are encoded, processed, and stored within the brain. In this review, we focus on recent advances in our understanding of the molecular mechanisms that underlie short-term, intermediate-term, and long-term forms of implicit memory in the marine invertebrate Aplysia californica, and consider how the conservation of common elements in each form may contribute to the different temporal phases of memory storage.

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    • "Neurobiology of Learning and Memory (2014), long-term memory in other organisms. While transcription is not 202 required for temporal phases other than long-term memory, 203 protein translation is required for intermediate-term (1–3 h) 204 phases of memory (Davis & Squire, 1984; Ghirardi et al., 1995; 205 Hawkins et al., 2006 "
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    ABSTRACT: 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 C. 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 one hour. 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 30 minutes after training, intermediate-term memory, tested 1 hour after training, and forgetting, tested 2 hours 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.
    Neurobiology of Learning and Memory 11/2014; 115. DOI:10.1016/j.nlm.2014.07.011 · 3.65 Impact Factor
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    • "For example in Aplysia, long-term facilitation provides a cellular correlate for behavioral sensitization that can be investigated in reduced preparations and cultured neurons (see for example Kandel, 2001; Hawkins et al., 2006). In a semi-intact reduced preparation in which the siphon and tail are exposed with the nerves connecting the ganglia left intact, intermediate and long-term sensitization can be studied for either the tail-siphon withdrawal reflex or for a tail-tail withdrawal reflex (Philips et al., 2006, 2011). "
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    ABSTRACT: Across phylogeny, the endogenous biological clock has been recognized as providing adaptive advantages to organisms through coordination of physiological and behavioral processes. Recent research has emphasized the role of circadian modulation of memory in generating peaks and troughs in cognitive performance. The circadian clock along with homeostatic processes also regulates sleep, which itself impacts the formation and consolidation of memory. Thus, the circadian clock, sleep and memory form a triad with ongoing dynamic interactions. With technological advances and the development of a global 24/7 society, understanding the mechanisms underlying these connections becomes pivotal for development of therapeutic treatments for memory disorders and to address issues in cognitive performance arising from non-traditional work schedules. Invertebrate models, such as Drosophila melanogaster and the mollusks Aplysia and Lymnaea, have proven invaluable tools for identification of highly conserved molecular processes in memory. Recent research from invertebrate systems has outlined the influence of sleep and the circadian clock upon synaptic plasticity. In this review, we discuss the effects of the circadian clock and sleep on memory formation in invertebrates drawing attention to the potential of in vivo and in vitro approaches that harness the power of simple invertebrate systems to correlate individual cellular processes with complex behaviors. In conclusion, this review highlights how studies in invertebrates with relatively simple nervous systems can provide mechanistic insights into corresponding behaviors in higher organisms and can be used to outline possible therapeutic options to guide further targeted inquiry.
    Frontiers in Systems Neuroscience 08/2014; 8:133. DOI:10.3389/fnsys.2014.00133
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    • "The sea hare Aplysia californica, like many invertebrates, has a remarkable ability to regenerate injured portions of the central nervous system789. This regenerative capacity, along with the readily identifyable individual neurons and populations, has allowed researchers to recreate specific snaptic circuits in vitro1011. Isolated Aplysia neurons have also become valuable tools for investigating the basic biology of neurite growth and regeneration. "
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    ABSTRACT: We have investigated Aplysia hemolymph as a source of endogenous factors to promote regeneration of bag cell neurons. We describe a novel synergistic effect between substrate-bound hemolymph proteins and laminin. This combination increased outgrowth and branching relative to either laminin or hemolymph alone. Notably, the addition of hemolymph to laminin substrates accelerated growth cone migration rate over ten-fold. Our results indicate that the active factor is either a high molecular weight protein or protein complex and is not the respiratory protein hemocyanin. Substrate-bound factor(s) from central nervous system-conditioned media also had a synergistic effect with laminin, suggesting a possible cooperation between humoral proteins and nervous system extracellular matrix. Further molecular characterization of active factors and their cellular targets is warranted on account of the magnitude of the effects reported here and their potential relevance for nervous system repair.
    Scientific Reports 07/2014; 4:4617. DOI:10.1038/srep04617 · 5.58 Impact Factor
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