Latent memory for sensitization in <i>Aplysia</i>

Philips, Gary T.; Tzvetkova, Ekaterina I.; Marinesco, Stéphane; Carew, Thomas

doi:10.1101/lm.111506

Cited by 36 publications

(50 citation statements)

References 41 publications

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“…The conclusion of our study is consistent with the previously reported findings of Philips et al (2006). Specifically, LTS training of Aplysia has not only overt but also latent learning effects.…”

Section: Learning and Memory 423supporting

confidence: 83%

“…Had the modulatory component of the network been potentiated by 4-d training, sensitization would have become apparent earlier than 25 min after BST (i.e., at the 15-min time point). This study thus, along with the recent report by Philips et al (2006), constitutes an initial step in the cellular and molecular characterization of biological processes that can facilitate learning and memory. Long-term sensitization training primes the animal for further learning.…”

Section: Learning and Memory 423mentioning

confidence: 99%

“…If present in simple model systems, like Aplysia, latent learning could be readily analyzed at the cellular and molecular levels. An instance of latent learning in Aplysia was recently reported by Philips et al (2006), who found that animals that had been previously trained for LTS displayed facilitated acquisition of further learning after the original long-term memory had decayed with time (i.e., memory savings). Moreover, animals that had failed to show long-term memory following training, subsequently displayed facilitated acquisition of sensitization.…”

mentioning

confidence: 99%

“…Moreover, animals that had failed to show long-term memory following training, subsequently displayed facilitated acquisition of sensitization. It is noteworthy that in the Philips et al (2006) study, LTS was induced with a single training session, Figure 1. Protocol for sensitization training.…”

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confidence: 99%

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Long-term sensitization training primes Aplysia for further learning

Antzoulatos

Wainwright²,

Cleary

et al. 2006

Learn. Mem.

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Repetitive, unilateral stimulation of Aplysia induces long-term sensitization (LTS) of ipsilaterally elicited siphon-withdrawal responses. Whereas some morphological effects of training appear only on ipsilateral sensory neurons, others appear bilaterally. We tested the possibility that contralateral morphological modifications may have functional significance. Therefore, we examined whether LTS training primes subsequent sensitization. Twenty-four hours after LTS training the effects of brief shock treatment (BST) were examined. BST failed to sensitize animals that had previously received either 4-d control treatment or 4-d ipsilateral LTS training. In contrast, BST did sensitize animals that had previously received 4-d contralateral LTS training, suggesting the presence of a latent trace that primes the animal for further learning.The siphon withdrawal reflex of Aplysia is a useful model system for understanding the neurobiology of learning and memory. The reflex exhibits sensitization, a simple form of learning, in which responses elicited by weak test stimuli are augmented by training with strong, usually noxious, stimuli (Carew et al. 1971;Pinsker et al. 1973;Scholz and Byrne 1987). Short-term sensitization (lasting from seconds to minutes) relies on covalent modification of pre-existing proteins. Intermediate-term sensitization (from minutes to hours) requires translation of mRNA into protein but does not require gene transcription. Long-term sensitization (LTS) (lasting days) requires both gene transcription and translation (Sutton et al. 2001). A critical locus of learning-related plasticity is the glutamatergic synapse of sensory neurons onto target motor neurons (Antzoulatos and Byrne 2004). Several experimental observations have suggested that LTS is partly mediated by structural changes of sensory neurons, which maintain sensorimotor synapses in a facilitated state (Bailey and Chen 1983;Wainwright et al. 2002).Twenty-four hours after LTS training on the lateral body wall of intact Aplysia, the siphon withdrawal reflex is sensitized only when evoked by test stimuli on the side of the tail ipsilateral to the trained body wall. When test stimulation is delivered to the contralateral side of the tail, siphon responses are normal (i.e., non-sensitized), similar to the responses of untrained animals (Wainwright et al. 2002). The ipsilateral effect of unilateral training suggests that a critical part of memory may be stored in the ipsilateral pleural-pedal ganglia, that is, the part of the Aplysia central nervous system that mediates the afferent limb of the reflex. Consequently, sensory neurons of only the ipsilateral ganglia would be expected to change after LTS training. Indeed, the number of sensorimotor appositions and the amplitude of sensorimotor excitatory postsynaptic potentials increased only on the ipsilateral side of trained animals. Surprisingly, other structural features of sensory neurons, such as the number of varicosities and the length of neurites, did change on the contralateral side (Wai...

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Section: Learning and Memory 423supporting

confidence: 83%

Section: Learning and Memory 423mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Long-term sensitization training primes Aplysia for further learning

Antzoulatos

Wainwright²,

Cleary

et al. 2006

Learn. Mem.

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“…CIHR Author Manuscript CIHR Author Manuscript [22,23]. In cultures, these messages might already be present at the synapse because of the synaptic growth induced by culturing the neurons.…”

Section: Cihr Author Manuscriptmentioning

confidence: 99%

Defining memories by their distinct molecular traces

Sossin

2008

Trends in Neurosciences

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It is often stated that short-term memory is consolidated in a protein-synthesis-dependent manner into long-term memory. Alternatively, memories might consist of distinct molecular traces that last for different periods of time. These traces can be graded by their 'volatility'; traces encoded by activation of protein kinases are more volatile than traces encoded by morphological changes at preexisting synapses. The least volatile ('static') traces are due to the generation and stabilization of new synapses. Importantly, whereas at the cellular level these traces are generated independently of each other, they might be linked at the network level where volatile memory traces are required to set up a cellular network that is in turn required to induce the static memory trace. Thinking about memory in terms of the molecular traceMemories are defined by behavioral experiments, where the distinction between short-term and long-term memory is time based and the conversion of short-term to long-term memory is called 'consolidation.' I propose that it is preferable to use a biochemical-based differentiation of memory traces that does not depend on absolute time but on the mechanism of the molecular trace. In computer science, the terms 'volatile' and 'static' differentiate types of memory. For example, memory that is stored in the state of a transistor requires constant input and is termed volatile, whereas memory stored on a magnetic disc does not require constant input and is termed static. Memories in the brain can also be differentiated based on the physical trace underlying the memory; however, unlike computer memory that either requires constant input or does not, physical memory traces are graded based on how long they last and how easily they are maintained. I will use the terms from computer science, volatile and static, to define this characteristic of memory traces, although this is not meant to imply an isomorphic relationship between computer and neuronal memory storage. Memory traces that depend on modification of preexisting proteins (such as phosphorylation) will be more volatile than those that depend on changes in protein levels, and these in turn will be more volatile than those due to morphological changes (Figure 1). CIHR Author Manuscript CIHR Author Manuscript CIHR Author Manuscript Serial versus parallel pathways for memory formation: the three little pigsAre volatile memory traces made into static memory traces through consolidation, or are distinct volatile and static memory traces initiated after experience? An instructive analogy is to envision that the static memory trace is a brick house. If volatile traces are stabilized into static memories, the structure of the house would be built as a volatile memory, stabilized by adding plaster and then consolidated by adding bricks. This model is implicit in the term 'consolidation' or when we talk about the 'conversion' of short-to long-term memory. By contrast, memory traces might resemble the houses built by the three little pigs, with t...

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High loads induce differences between actual and imagined movement duration

Slifkin

2007

Exp Brain Res

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Actual and imagined action may be governed by common information and neural processes. This hypothesis has found strong support from a range of chronometric studies showing that it takes the same amount of time to actually move and to imagine moving. However, exceptions have been observed when actual and imagined movements were made under conditions of inertial loading: sometimes the equivalency of actual and imagined movement durations (MDs) has been preserved, and other times it has been disrupted. The purpose of the current study was to test the hypothesis that the appearance and magnitude of actual-imagined MD differences in those studies was dependent on the level of load relative to the maximum loading capacity of the involved effector system [the maximum voluntary load (MVL)]. The experiment required 12 young, healthy humans to actually produce, and to imagine producing, single degree of freedom index finger movements under a range of loads (0, 5, 10, 20, 40, and 80% MVL). As predicted, statistically significant actual-imagined MD differences were absent at lower loads (0-20% MVL), but differences appeared and increased in magnitude with further increases in %MVL (40 and 80% MVL). That pattern of results may relate to the common, everyday experience individuals have in interacting with loads. Participants are likely to have extensive experience interacting with very low loads, but not high loads. It follows that the control of low inertial loads should be governed by complete central representations of action, while representations should be less complete for high loads. A consequence may be increases in the uncertainty of predicting motor output with increases in load. Compensation for the increased uncertainty may appear as increases in the MD values selected during both the preparation and imagery of action--according to a speed-uncertainty trade-off. Then, during actual action, MD may be reduced if movement-related feedback indicates that a faster movement would succeed.

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Latent memory for sensitization in Aplysia

Cited by 36 publications

References 41 publications

Long-term sensitization training primes Aplysia for further learning

Long-term sensitization training primes Aplysia for further learning

Defining memories by their distinct molecular traces

High loads induce differences between actual and imagined movement duration

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