Chapter 7: Memory reconsolidation and Extinction in invertebrates: Evolutionary conserved characteristics of memory reprocessing and restabilization

MARÍA E PEDREIRA; ARTURO ROMANO

Memory Reconsolidation

Elsevier

Lugar: London; Año: 2013;

7.1 INTRODUCTIONThe concept of memory consolidation was established by pioneer studies onhuman memory by M€uller and Pilzecker (1900) and was further formalizedafter the accumulation of experimental evidence on retrograde amnesia inrodents (McGaugh, 1966). The requirement of both transcription and translationMemory Reconsolidation. http://dx.doi.org/10.1016/B978-0-12-386892-3.00007-XCopyright
2013 Elsevier Inc. All rights reserved.139during a discrete period of time after acquisition has become widely accepted formemory stabilization and persistence (Davis & Squire, 1984; Kandel, 2004).According to the classical version of consolidation theory, once stability isreached, memory becomes resistant to further challenges over time. However,soon after the formalization of the theory, the studies of Lewis and Misanin(Lewis, 1979; Lewis & Maher, 1965; Misanin, Miller, & Lewis, 1968) on cuedependentamnesia suggested, for the first time, that the process was morecomplex and pointed to a more dynamic nature of memory processing. Thephenomenon of cue-dependent amnesia states that a consolidated memory canundergo retrograde amnesia if a cue or reminder is presented just prior to the disruptingagent. The concept was later extended to the possibility of post-retrievalmemory enhancement (Devietti, Conger, & Kirkpatrick, 1977). According to theoriginal formulation of these authors, the modulation of memory occurs onlywhen memory is activedthat is, initially, during, and soon after acquisitionand later, when memory is reactivated. Reactivation can be spontaneous or canbe induced by internal or external events, such as the presence of a reminder.Twenty years later, the idea of memory labilization and reprocessing afterretrieval was recovered (Nader, Schafe, & LeDoux, 2000; Przybyslawski &Sara, 1997) and was termed reconsolidation. Such an idea gained interest inthe neurobiological community not only because of its theoretical and mechanisticimportance but also because of its potential application in therapeutic strategiesfor memory-related pathologies.After a decade of intense studies in this field, the concepts of cue-dependentamnesia and reconsolidation have become more complex and have been integratedinto a more comprehensive hypothesis, as discussed in other chapters inthis book. In addition, the concepts are now integrated with the study ofanother retrieval-dependent process, memory extinction. The study of memoryhas also advanced to encompass knowledge of the molecular mechanismsinvolved in both reconsolidation and extinction.However, the initial studies mentioned previously, and many subsequentstudies, focused mainly on rodent models of memory reconsolidation.Despite the unquestioned value of the rodent studies, a question soon aroseregarding the universality of this phenomenon:Was reconsolidation a particularcharacteristic of rodents or mammals?In this chapter, we focus on findings obtained using a contextesignalmemory model in crabs and describe the parametrical conditions for memorylabilization and reconsolidation. We also review the studies at the mechanisticlevel, describing the molecular features involved in memory reconsolidationand extinction. Then, on the basis of the findings in crab studies, we presentcomparative studies in rodents that are performed using another contextualmemory paradigm, fear conditioning.A wide variety of animal models, ranging from Caenorhabditis elegans tohumans, are available for the study of memory. Each model system has benefitsand drawbacks. Using this broad spectrum of species, learning and memoryhave been studied at the behavioral, systems, neuronal, and subcellular140 Memory Reconsolidation and Extinction in Invertebrateslevels. Invertebrate models have provided central insights into the underlyingmechanisms of learning and memory formation (Carew, 2000; Kandel, 2004).Research using nonhuman animals has produced more than 300 papers onreconsolidation in the past 10 years alone, and invertebrate research accountedfor approximately 10% of these. Many invertebrate models can be used to studymemory. However, to our knowledge, only seven invertebrate models havebeen used to study the process of reconsolidation: the terrestrial slug Limax(Sekiguchi, Yamad, & Suzuki, 1997), the pond snail Lymnaea (Sangha,Scheibenstock, & Lukowiak, 2003), the terrestrial snail Helix locorum(Gainutdinova et al., 2005), the mollusk Hermissenda (Child, Epstein, Kuzirian& Alkon 2003), the worm Caenorhabditis elegans (Rose & Rankin, 2006), thehoneybee Apis melifera (Stollhoff, Menzel, & Eisenhardt, 2008), and the crabChasmagnatus. Although the results on reconsolidation obtained in thementioned models are important, due to space limitations, this chapterfocuses on the contextesignal memory in the crab Chasmagnatus.