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Miranda P, Mirisis AA, Kukushkin NV, Carew TJ. Pattern detection in the TGFβ cascade controls the induction of long-term synaptic plasticity. Proc Natl Acad Sci U S A 2023; 120:e2300595120. [PMID: 37748056 PMCID: PMC10556637 DOI: 10.1073/pnas.2300595120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 08/11/2023] [Indexed: 09/27/2023] Open
Abstract
Transforming growth factor β (TGFβ) is required for long-term memory (LTM) for sensitization in Aplysia. When LTM is induced using a two-trial training protocol, TGFβ inhibition only blocks LTM when administrated at the second, not the first trial. Here, we show that TGFβ acts as a "repetition detector" during the induction of two-trial LTM. Secretion of the biologically inert TGFβ proligand must coincide with its proteolytic activation by the Bone morphogenetic protein-1 (BMP-1/Tolloid) metalloprotease, which occurs specifically during trial two of our two-trial training paradigm. This paradigm establishes long-term synaptic facilitation (LTF), the cellular correlate of LTM. BMP-1 application paired with a single serotonin (5HT) pulse induced LTF, whereas neither a single 5HT pulse nor BMP-1 alone effectively did so. On the other hand, inhibition of endogenous BMP-1 activity blocked the induction of two-trial LTF. These results suggest a unique role for TGFβ in the interaction of repeated trials: during learning, repeated stimuli engage separate steps of the TGFβ cascade that together are necessary for the induction of long-lasting memories.
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Affiliation(s)
- Paige Miranda
- Center for Neural Science, New York University, New York, NY10003
| | | | - Nikolay V. Kukushkin
- Center for Neural Science, New York University, New York, NY10003
- Liberal Studies, New York University, New York, NY10003
| | - Thomas J. Carew
- Center for Neural Science, New York University, New York, NY10003
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2
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Kukushkin NV, Williams SP, Carew TJ. Neurotropic and modulatory effects of insulin-like growth factor II in Aplysia. Sci Rep 2019; 9:14379. [PMID: 31591438 PMCID: PMC6779898 DOI: 10.1038/s41598-019-50923-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 09/12/2019] [Indexed: 01/19/2023] Open
Abstract
Insulin-like growth factor II (IGF2) enhances memory in rodents via the mannose-6-phosphate receptor (M6PR), but the underlying mechanisms remain poorly understood. We found that human IGF2 produces an enhancement of both synaptic transmission and neurite outgrowth in the marine mollusk Aplysia californica. These findings were unexpected since Aplysia lack the mammal-specific affinity between insulin-like ligands and M6PR. Surprisingly, this effect was observed in parallel with a suppression of neuronal excitability in a well-understood circuit that supports several temporally and mechanistically distinct forms of memory in the defensive withdrawal reflex, suggesting functional coordination between excitability and memory formation. We hypothesize that these effects represent behavioral adaptations to feeding that are mediated by the endogenous Aplysia insulin-like system. Indeed, the exogenous application of a single recombinant insulin-like peptide cloned from the Aplysia CNS cDNA replicated both the enhancement of synaptic transmission, the reduction of excitability, and promoted clearance of glucose from the hemolymph, a hallmark of bona fide insulin action.
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Affiliation(s)
| | | | - Thomas James Carew
- Center for Neural Science, New York University, 4 Washington Pl, New York, NY, 10003, USA.
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3
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Farruggella J, Acebo J, Lloyd L, Wainwright ML, Mozzachiodi R. Role of nitric oxide in the induction of the behavioral and cellular changes produced by a common aversive stimulus in Aplysia. Behav Brain Res 2018; 360:341-353. [PMID: 30528940 DOI: 10.1016/j.bbr.2018.12.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 12/04/2018] [Accepted: 12/05/2018] [Indexed: 10/27/2022]
Abstract
Although it is well documented that exposure to aversive stimuli induces modulation of neural circuits and subsequent behavioral changes, the means by which an aversive stimulus concomitantly alters behaviors of different natures (e.g., defensive and appetitive) remains unclear. Here, we addressed this issue by using the learning-induced concurrent modulation of defensive and appetitive behaviors that occurs when the mollusk Aplysia is exposed to aversive stimuli. In Aplysia, aversive stimuli concomitantly enhance withdrawal reflexes (i.e., sensitization) and suppress feeding. Sensitization and feeding suppression, which are expressed in the short term and long term, depending on the training protocol, are accompanied by increased excitability of the tail sensory neurons (TSNs) controlling the withdrawal reflexes, and by decreased excitability of feeding decision-making neuron B51, respectively. Serotonin (5-HT) has been shown to mediate sensitization, but not feeding suppression. In this study, we examined which other neurotransmitter might be responsible for feeding suppression and its underlying cellular changes. Our results indicate that nitric oxide (NO) contributes to both short-term and long-term feeding suppression, as well as to the underlying decreased B51 excitability. NO was also necessary for the induction of long-term sensitization and for the expression of short-term increased TSN excitability in vitro, revealing a previously undocumented interaction between 5-HT and NO signaling cascades in sensitization. Overall, these results revealed a scenario in which multiple modulators contribute to the widespread changes induced by sensitizing stimuli in Aplysia.
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Affiliation(s)
- Jesse Farruggella
- Department of Life Sciences, Texas A&M University - Corpus Christi, 6300 Ocean Drive, Unit 5800, Corpus Christi, TX, 78412, USA
| | - Jonathan Acebo
- Department of Life Sciences, Texas A&M University - Corpus Christi, 6300 Ocean Drive, Unit 5800, Corpus Christi, TX, 78412, USA
| | - Leah Lloyd
- Department of Life Sciences, Texas A&M University - Corpus Christi, 6300 Ocean Drive, Unit 5800, Corpus Christi, TX, 78412, USA
| | - Marcy L Wainwright
- Department of Life Sciences, Texas A&M University - Corpus Christi, 6300 Ocean Drive, Unit 5800, Corpus Christi, TX, 78412, USA
| | - Riccardo Mozzachiodi
- Department of Life Sciences, Texas A&M University - Corpus Christi, 6300 Ocean Drive, Unit 5800, Corpus Christi, TX, 78412, USA.
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4
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Leod KAM, Seas A, Wainwright ML, Mozzachiodi R. Effects of internal and external factors on the budgeting between defensive and non-defensive responses in Aplysia. Behav Brain Res 2018; 349:177-185. [PMID: 29704600 DOI: 10.1016/j.bbr.2018.04.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 03/23/2018] [Accepted: 04/13/2018] [Indexed: 10/17/2022]
Abstract
Following exposure to aversive stimuli, organisms budget their behaviors by augmenting defensive responses and reducing/suppressing non-defensive behaviors. This budgeting process must be flexible to accommodate modifications in the animal's internal and/or external state that require the normal balance between defensive and non-defensive behaviors to be adjusted. When exposed to aversive stimuli, the mollusk Aplysia budgets its behaviors by concurrently enhancing defensive withdrawal reflexes (an elementary form of learning known as sensitization) and suppressing feeding. Sensitization and feeding suppression are consistently co-expressed following different training protocols and share common temporal domains, suggesting that they are interlocked. In this study, we attempted to uncouple the co-expression of sensitization and feeding suppression using: 1) manipulation of the animal's motivational state through prolonged food deprivation and 2) extended training with aversive stimuli that induces sensitization lasting for weeks. Both manipulations uncoupled the co-expression of the above behavioral changes. Prolonged food deprivation prevented the expression of sensitization, but not of feeding suppression. Following the extended training, sensitization and feeding suppression were co-expressed only for a limited time (i.e., 24 h), after which feeding returned to baseline levels as sensitization persisted for up to seven days. These findings indicate that sensitization and feeding suppression are not interlocked and that their co-expression can be uncoupled by internal (prolonged food deprivation) and external (extended aversive training) factors. The different strategies, by which the co-expression of sensitization and feeding suppression was altered, provide an example of how budgeting strategies triggered by an identical aversive experience can vary depending on the state of the organism.
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Affiliation(s)
- Kaitlyn A Mac Leod
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, TX, 78412, USA
| | - Alexandra Seas
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, TX, 78412, USA
| | - Marcy L Wainwright
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, TX, 78412, USA
| | - Riccardo Mozzachiodi
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, TX, 78412, USA.
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5
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Weisz HA, Wainwright ML, Mozzachiodi R. A novel in vitro analog expressing learning-induced cellular correlates in distinct neural circuits. ACTA ACUST UNITED AC 2017; 24:331-340. [PMID: 28716953 PMCID: PMC5516688 DOI: 10.1101/lm.045229.117] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Accepted: 05/12/2017] [Indexed: 01/29/2023]
Abstract
When presented with noxious stimuli, Aplysia exhibits concurrent sensitization of defensive responses, such as the tail-induced siphon withdrawal reflex (TSWR) and suppression of feeding. At the cellular level, sensitization of the TSWR is accompanied by an increase in the excitability of the tail sensory neurons (TSNs) that elicit the reflex, whereas feeding suppression is accompanied by decreased excitability of B51, a decision-making neuron in the feeding neural circuit. The goal of this study was to develop an in vitro analog coexpressing the above cellular correlates. We used a reduced preparation consisting of buccal, cerebral, and pleural-pedal ganglia, which contain the neural circuits controlling feeding and the TSWR, respectively. Sensitizing stimuli were delivered in vitro by electrical stimulation of afferent nerves. When trained with sensitizing stimuli, the in vitro analog expressed concomitant increased excitability in TSNs and decreased excitability in B51, which are consistent with the occurrence of sensitization and feeding suppression induced by in vivo training. This in vitro analog expressed both short-term (15 min) and long-term (24 h) excitability changes in TSNs and B51, depending on the amount of training administered. Finally, in vitro application of serotonin increased TSN excitability without altering B51 excitability, mirroring the in vivo application of the monoamine that induces sensitization, but not feeding suppression.
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Affiliation(s)
- Harris A Weisz
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, Texas 78412, USA
| | - Marcy L Wainwright
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, Texas 78412, USA
| | - Riccardo Mozzachiodi
- Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, Texas 78412, USA
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Yang X, Fang Y, Yu Z, Wang Z, Zhang T, Yin M, Lin M, Yang Y, Cai Y, Huang R. Nonassociative learning implementation by a single memristor-based multi-terminal synaptic device. NANOSCALE 2016; 8:18897-18904. [PMID: 27714050 DOI: 10.1039/c6nr04142f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Animals' survival is dependent on their abilities to adapt to the changing environment by adjusting their behaviours, which is related to the ubiquitous learning behaviour, nonassociative learning. Thus mimicking the indispensable learning behaviour in organisms based on electronic devices is vital to better achieve artificial neural networks and neuromorphic computing. Here a three terminal device consisting of an oxide-based memristor and a NMOS transistor is proposed. The memristor with gradual conductance tuning inherently functions as the synapse between sensor neurons and motor neurons and presents adjustable synaptic plasticity, while the NMOS transistor attached to the memristor is utilized to mimic the modulatory effect of the neuromodulator released by inter neurons. Such a memristor-based multi-terminal device allows the practical implementation of significant nonassociative learning based on a single electronic device. In this study, the experience-induced modification behaviour, both habituation and sensitization, was successfully achieved. The dependence of the nonassociative behavioural response on the strength and interval of presented stimuli was also discussed. The implementation of nonassociative learning offers feasible and experimental advantages for further study on neuromorphic systems based on electronic devices.
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Affiliation(s)
- Xue Yang
- Institute of Microelectronics, Peking University, 100871, Beijing, China
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Mirisis AA, Alexandrescu A, Carew TJ, Kopec AM. The Contribution of Spatial and Temporal Molecular Networks in the Induction of Long-term Memory and Its Underlying Synaptic Plasticity. AIMS Neurosci 2016; 3:356-384. [PMID: 27819030 PMCID: PMC5096789 DOI: 10.3934/neuroscience.2016.3.356] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ability to form long-lasting memories is critical to survival and thus is highly conserved across the animal kingdom. By virtue of its complexity, this same ability is vulnerable to disruption by a wide variety of neuronal traumas and pathologies. To identify effective therapies with which to treat memory disorders, it is critical to have a clear understanding of the cellular and molecular mechanisms which subserve normal learning and memory. A significant challenge to achieving this level of understanding is posed by the wide range of distinct temporal and spatial profiles of molecular signaling induced by learning-related stimuli. In this review we propose that a useful framework within which to address this challenge is to view the molecular foundation of long-lasting plasticity as composed of unique spatial and temporal molecular networks that mediate signaling both within neurons (such as via kinase signaling) as well as between neurons (such as via growth factor signaling). We propose that evaluating how cells integrate and interpret these concurrent and interacting molecular networks has the potential to significantly advance our understanding of the mechanisms underlying learning and memory formation.
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Affiliation(s)
- Anastasios A. Mirisis
- Center for Neural Science, New York University, New York, NY, USA
- Department of Biology, New York University, New York, NY, USA
| | - Anamaria Alexandrescu
- Center for Neural Science, New York University, New York, NY, USA
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY, USA
| | - Thomas J. Carew
- Center for Neural Science, New York University, New York, NY, USA
| | - Ashley M. Kopec
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA
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Kempsell AT, Fieber LA. Age-related deficits in synaptic plasticity rescued by activating PKA or PKC in sensory neurons of Aplysia californica. Front Aging Neurosci 2015; 7:173. [PMID: 26388769 PMCID: PMC4558425 DOI: 10.3389/fnagi.2015.00173] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 08/19/2015] [Indexed: 01/31/2023] Open
Abstract
Brain aging is associated with declines in synaptic function that contribute to memory loss, including reduced postsynaptic response to neurotransmitters and decreased neuronal excitability. To understand how aging affects memory in a simple neural circuit, we studied neuronal proxies of memory for sensitization in mature vs. advanced age Aplysia californica (Aplysia). L-Glutamate- (L-Glu-) evoked excitatory currents were facilitated by the neuromodulator serotonin (5-HT) in sensory neurons (SN) isolated from mature but not aged animals. Activation of protein kinase A (PKA) and protein kinase C (PKC) signaling rescued facilitation of L-Glu currents in aged SN. Similarly, PKA and PKC activators restored increased excitability in aged tail SN. These results suggest that altered synaptic plasticity during aging involves defects in second messenger systems.
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Affiliation(s)
- Andrew T Kempsell
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami Miami, FL, USA
| | - Lynne A Fieber
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami Miami, FL, USA
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9
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Kopec AM, Philips GT, Carew TJ. Distinct Growth Factor Families Are Recruited in Unique Spatiotemporal Domains during Long-Term Memory Formation in Aplysia californica. Neuron 2015; 86:1228-39. [PMID: 26050041 PMCID: PMC4573621 DOI: 10.1016/j.neuron.2015.04.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Revised: 01/23/2015] [Accepted: 04/20/2015] [Indexed: 12/22/2022]
Abstract
Several growth factors (GFs) have been implicated in long-term memory (LTM), but no single GF can support all of the plastic changes that occur during memory formation. Because GFs engage highly convergent signaling cascades that often mediate similar functional outcomes, the relative contribution of any particular GF to LTM is difficult to ascertain. To explore this question, we determined the unique contribution of distinct GF families (signaling via TrkB and TGF-βr-II) to LTM formation in Aplysia. We demonstrate that TrkB and TGF-βr-II signaling are differentially recruited during two-trial training in both time (by trial 1 or 2, respectively) and space (in distinct subcellular compartments). These GFs independently regulate MAPK activation and synergistically regulate gene expression. We also show that trial 1 TrkB and trial 2 TGF-βr-II signaling are required for LTM formation. These data support the view that GFs engaged in LTM formation are interactive components of a complex molecular network.
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Affiliation(s)
- Ashley M Kopec
- Center for Neural Science, New York University, New York, NY 10003
| | - Gary T Philips
- Center for Neural Science, New York University, New York, NY 10003
| | - Thomas J Carew
- Center for Neural Science, New York University, New York, NY 10003.
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10
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Kempsell AT, Fieber LA. Aging in Sensory and Motor Neurons Results in Learning Failure in Aplysia californica. PLoS One 2015; 10:e0127056. [PMID: 25970633 PMCID: PMC4430239 DOI: 10.1371/journal.pone.0127056] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/10/2015] [Indexed: 11/18/2022] Open
Abstract
The physiological and molecular mechanisms of age-related memory loss are complicated by the complexity of vertebrate nervous systems. This study takes advantage of a simple neural model to investigate nervous system aging, focusing on changes in learning and memory in the form of behavioral sensitization in vivo and synaptic facilitation in vitro. The effect of aging on the tail withdrawal reflex (TWR) was studied in Aplysia californica at maturity and late in the annual lifecycle. We found that short-term sensitization in TWR was absent in aged Aplysia. This implied that the neuronal machinery governing nonassociative learning was compromised during aging. Synaptic plasticity in the form of short-term facilitation between tail sensory and motor neurons decreased during aging whether the sensitizing stimulus was tail shock or the heterosynaptic modulator serotonin (5-HT). Together, these results suggest that the cellular mechanisms governing behavioral sensitization are compromised during aging, thereby nearly eliminating sensitization in aged Aplysia.
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Affiliation(s)
- Andrew T. Kempsell
- University of Miami, Rosenstiel School of Marine and Atmospheric Science, Department of Marine Biology and Ecology, Miami, Florida, United States of America
| | - Lynne A. Fieber
- University of Miami, Rosenstiel School of Marine and Atmospheric Science, Department of Marine Biology and Ecology, Miami, Florida, United States of America
- * E-mail:
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11
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Byrne JH, Hawkins RD. Nonassociative learning in invertebrates. Cold Spring Harb Perspect Biol 2015; 7:cshperspect.a021675. [PMID: 25722464 DOI: 10.1101/cshperspect.a021675] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The simplicity and tractability of the neural circuits mediating behaviors in invertebrates have facilitated the cellular/molecular dissection of neural mechanisms underlying learning. The review has a particular focus on the general principles that have emerged from analyses of an example of nonassociative learning, sensitization in the marine mollusk Aplysia. Learning and memory rely on multiple mechanisms of plasticity at multiple sites of the neuronal circuits, with the relative contribution to memory of the different sites varying as a function of the extent of training and time after training. The same intracellular signaling cascades that induce short-term modifications in synaptic transmission can also be used to induce long-term changes. Although short-term memory relies on covalent modifications of preexisting proteins, long-term memory also requires regulated gene transcription and translation. Maintenance of long-term cellular memory involves both intracellular and extracellular feedback loops, which sustain the regulation of gene expression and the modification of targeted molecules.
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Affiliation(s)
- John H Byrne
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, Texas 77030
| | - Robert D Hawkins
- Department of Neuroscience, Columbia University, New York, New York 10032 New York State Psychiatric Institute, New York, New York 10032
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12
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Abstract
STUDY OBJECTIVE To characterize sleep in the marine mollusk, Aplysia californica. DESIGN Animal behavior and activity were assessed using video recordings to measure activity, resting posture, resting place preference, and behavior after rest deprivation. Latencies for behavioral responses were measured for appetitive and aversive stimuli for animals in the wake and rest states. SETTING Circadian research laboratory for Aplysia. PATIENTS OR PARTICIPANTS A. californica from the Pacific Ocean. INTERVENTIONS N/A. MEASUREMENTS AND RESULTS Aplysia rest almost exclusively during the night in a semi-contracted body position with preferential resting locations in the upper corners of their tank. Resting animals demonstrate longer latencies in head orientation and biting in response to a seaweed stimulus and less frequent escape response steps following an aversive salt stimulus applied to the tail compared to awake animals at the same time point. Aplysia exhibit rebound rest the day following rest deprivation during the night, but not after similar handling stimulation during the day. CONCLUSIONS Resting behavior in Aplysia fulfills all invertebrate characteristics of sleep including: (1) a specific sleep body posture, (2) preferred resting location, (3) reversible behavioral quiescence, (4) elevated arousal thresholds for sensory stimuli during sleep, and (5) compensatory sleep rebound after sleep deprivation.
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Affiliation(s)
- Albrecht P.A. Vorster
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL; Present Address: Department of Medical Psychology and Behavioral Neurobiology and Center for Integrative Neuroscience CIN, University of Tübingen, Tübingen, Germany
| | - Harini C. Krishnan
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL
| | - Chiara Cirelli
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - Lisa C. Lyons
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL
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Michel M, Lyons LC. Unraveling the complexities of circadian and sleep interactions with memory formation through invertebrate research. Front Syst Neurosci 2014; 8:133. [PMID: 25136297 PMCID: PMC4120776 DOI: 10.3389/fnsys.2014.00133] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 07/07/2014] [Indexed: 12/14/2022] Open
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.
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Affiliation(s)
- Maximilian Michel
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine Nashville, TN, USA
| | - Lisa C Lyons
- Department of Biological Science, Program in Neuroscience, Florida State University Tallahassee, FL, USA
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14
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San Martín A, Pagani MR. Understanding intellectual disability through RASopathies. ACTA ACUST UNITED AC 2014; 108:232-9. [PMID: 24859216 DOI: 10.1016/j.jphysparis.2014.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 04/20/2014] [Accepted: 05/13/2014] [Indexed: 12/18/2022]
Abstract
Intellectual disability, commonly known as mental retardation in the International Classification of Disease from World Health Organization, is the term that describes an intellectual and adaptive cognitive disability that begins in early life during the developmental period. Currently the term intellectual disability is the preferred one. Although our understanding of the physiological basis of learning and learning disability is poor, a general idea is that such condition is quite permanent. However, investigations in animal models suggest that learning disability can be functional in nature and as such reversible through pharmacology or appropriate learning paradigms. A fraction of the cases of intellectual disability is caused by point mutations or deletions in genes that encode for proteins of the RAS/MAP kinase signaling pathway known as RASopathies. Here we examined the current understanding of the molecular mechanisms involved in this group of genetic disorders focusing in studies which provide evidence that intellectual disability is potentially treatable and curable. The evidence presented supports the idea that with the appropriate understanding of the molecular mechanisms involved, intellectual disability could be treated pharmacologically and perhaps through specific mechanistic-based teaching strategies.
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Affiliation(s)
- Alvaro San Martín
- Genetics of Learning Laboratory, Systems Neuroscience Section, Department of Physiology and Biophysics, School of Medicine, University of Buenos Aires, IFIBIO-Houssay-CONICET, C1121ABG Buenos Aires, Argentina
| | - Mario Rafael Pagani
- Genetics of Learning Laboratory, Systems Neuroscience Section, Department of Physiology and Biophysics, School of Medicine, University of Buenos Aires, IFIBIO-Houssay-CONICET, C1121ABG Buenos Aires, Argentina.
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15
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Fischer TM, Jacobson DA, Demorest-Hayes K. Network processes involved in the mediation of short-term habituation in Aplysia: contribution of intrinsic regulation of excitability and synaptic augmentation. Front Integr Neurosci 2014; 8:15. [PMID: 24592216 PMCID: PMC3923261 DOI: 10.3389/fnint.2014.00015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 01/28/2014] [Indexed: 11/22/2022] Open
Abstract
Short-term habituation (STH) is the decrease in behavioral responding observed during repeated stimulation at regular intervals. For siphon-elicited siphon withdrawal in Aplysia (S-SWR), we previously showed that the amplitude of responses measured in LFS-type siphon motor neurons (LFS MNs) during training is dependent on the stimulus interval used and is training-site specific. The major source of excitation from siphon stimulation onto the LFS MNs comes from the L29 interneurons. Here we examined the role of the L29s in STH by addressing two questions: (1) What are the relative contributions of intrinsic regulation of excitability and network inhibition on L29 activity during STH training? By activating L29s with intracellular current injection, we found that intrinsic changes in excitability occur, but only at short training intervals (1 s). We also demonstrated that network inhibition is not required for regulating L29 responses during training, indicating that any expression of inhibition is redundant to the excitability changes. (2) How does L29 synaptic plasticity contribute to the maintenance of training site-specificity exhibited in LFS MNs? When training stimuli are delivered 1 s apart [1 s, interstimulus interval (ISI)], L29 responses decrease in both stimulated (trained) and un-stimulated (untrained) pathways, yet site-specificity of training is maintained in the LFS MNs. Our results suggest that activity-dependent synaptic facilitation (augmentation; AUG) expressed by the L29s acts to compensate for the decreased activity in the untrained pathway. First, we demonstrated that the L29-LFS synapse exhibits significant AUG with L29 activation at a 1 s ISI. Second, we showed that the induction of AUG prevents the reduction in siphon-evoked LFS responses that is otherwise observed with decreased L29 activity. Collectively, our results support a role for the L29s in regulating network dynamics during STH training, but only at rapid (1 s ISI) training intervals.
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Affiliation(s)
- Thomas M Fischer
- Department of Psychology, Wayne State University Detroit, MI, USA
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Philips GT, Kopec AM, Carew TJ. Pattern and predictability in memory formation: from molecular mechanisms to clinical relevance. Neurobiol Learn Mem 2013; 105:117-24. [PMID: 23727358 PMCID: PMC4020421 DOI: 10.1016/j.nlm.2013.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/08/2013] [Accepted: 05/12/2013] [Indexed: 12/13/2022]
Abstract
Most long-term memories are formed as a consequence of multiple experiences. The temporal spacing of these experiences is of considerable importance: experiences distributed over time (spaced training) are more easily encoded and remembered than either closely spaced experiences, or a single prolonged experience (massed training). In this article, we first review findings from studies in animal model systems that examine the cellular and molecular properties of the neurons and circuits in the brain that underlie training pattern sensitivity during long-term memory (LTM) formation. We next focus on recent findings which have begun to elucidate the mechanisms that support inter-trial interactions during the induction of LTM. Finally, we consider the implications of these findings for developing therapeutic strategies to address questions of direct clinical relevance.
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Affiliation(s)
- Gary T Philips
- Center for Neural Science, New York University, 4 Washington Place, Room 809, New York, NY 10003, United States.
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Philips GT, Ye X, Kopec AM, Carew TJ. MAPK establishes a molecular context that defines effective training patterns for long-term memory formation. J Neurosci 2013; 33:7565-73. [PMID: 23616561 PMCID: PMC3865502 DOI: 10.1523/jneurosci.5561-12.2013] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 03/19/2013] [Accepted: 03/20/2013] [Indexed: 12/23/2022] Open
Abstract
Although the importance of spaced training trials in the formation of long-term memory (LTM) is widely appreciated, surprisingly little is known about the molecular mechanisms that support interactions between individual trials. The intertrial dynamics of ERK/MAPK activation have recently been correlated with effective training patterns for LTM. However, whether and how MAPK is required to mediate intertrial interactions remains unknown. Using a novel two-trial training pattern which induces LTM in Aplysia, we show that the first of two training trials recruits delayed protein synthesis-dependent nuclear MAPK activity that establishes a unique molecular context involving the recruitment of CREB kinase and ApC/EBP and is an essential intertrial signaling mechanism for LTM induction. These findings provide the first demonstration of a requirement for MAPK in the intertrial interactions during memory formation and suggest that the kinetics of MAPK activation following individual experiences determines effective training intervals for LTM formation.
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Affiliation(s)
- Gary T. Philips
- Center for Neural Science, New York University, New York, New York 10003
| | - Xiaojing Ye
- Center for Neural Science, New York University, New York, New York 10003
| | - Ashley M. Kopec
- Center for Neural Science, New York University, New York, New York 10003
| | - Thomas J. Carew
- Center for Neural Science, New York University, New York, New York 10003
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Dacks AM, Weiss KR. Release of a single neurotransmitter from an identified interneuron coherently affects motor output on multiple time scales. J Neurophysiol 2013; 109:2327-34. [PMID: 23407357 DOI: 10.1152/jn.01079.2012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Neurotransmitters can have diverse effects that occur over multiple time scales often making the consequences of neurotransmission difficult to predict. To explore the consequences of this diversity, we used the buccal ganglion of Aplysia to examine the effects of GABA release by a single interneuron, B40, on the intrinsic properties and motor output of the radula closure neuron B8. B40 induces a picrotoxin-sensitive fast IPSP lasting milliseconds in B8 and a slow EPSP lasting seconds. We found that the excitatory effects of this slow EPSP are also mediated by GABA. Together, these two GABAergic actions structure B8 firing in a pattern characteristic of ingestive programs. Furthermore, we found that repeated B40 stimulation induces a persistent increase in B8 excitability that was occluded in the presence of the GABA B receptor agonist baclofen, suggesting that GABA affects B8 excitability over multiple time scales. The phasing of B8 activity during the feeding motor programs determines the nature of the behavior elicited during that motor program. The persistent increase in B8 excitability induced by B40 biased the activity of B8 during feeding motor programs causing the motor programs to become more ingestive in nature. Thus, a single transmitter released from a single interneuron can have consequences for motor output that are expressed over multiple time scales. Importantly, despite the differences in their signs and temporal characteristics, the three actions of B40 are coherent in that they promote B8 firing patterns that are characteristic of ingestive motor outputs.
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Affiliation(s)
- Andrew M Dacks
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY, USA.
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Local synaptic integration of mitogen-activated protein kinase and protein kinase A signaling mediates intermediate-term synaptic facilitation in Aplysia. Proc Natl Acad Sci U S A 2012; 109:18162-7. [PMID: 23071303 DOI: 10.1073/pnas.1209956109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is widely appreciated that memory processing engages a wide range of molecular signaling cascades in neurons, but how these cascades are temporally and spatially integrated is not well understood. To explore this important question, we used Aplysia californica as a model system. We simultaneously examined the timing and subcellular location of two signaling molecules, MAPK (ERK1/2) and protein kinase A (PKA), both of which are critical for the formation of enduring memory for sensitization. We also explored their interaction during the formation of enduring synaptic facilitation, a cellular correlate of memory, at tail sensory-to-motor neuron synapses. We find that repeated tail nerve shock (TNS, an analog of sensitizing training) immediately and persistently activates MAPK in both sensory neuron somata and synaptic neuropil. In contrast, we observe immediate PKA activation only in the synaptic neuropil. It is followed by PKA activation in both compartments 1 h after TNS. Interestingly, blocking MAPK activation during, but not after, TNS impairs PKA activation in synaptic neuropil without affecting the delayed PKA activation in sensory neuron somata. Finally, by applying inhibitors restricted to the synaptic compartment, we show that synaptic MAPK activation during TNS is required for the induction of intermediate-term synaptic facilitation, which leads to the persistent synaptic PKA activation required to maintain this facilitation. Collectively, our results elucidate how MAPK and PKA signaling cascades are spatiotemporally integrated in a single neuron to support synaptic plasticity underlying memory formation.
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Computational design of enhanced learning protocols. Nat Neurosci 2011; 15:294-7. [PMID: 22197829 PMCID: PMC3267874 DOI: 10.1038/nn.2990] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/28/2011] [Indexed: 11/08/2022]
Abstract
Learning and memory are influenced by the temporal pattern of training stimuli. However, the mechanisms that determine the effectiveness of a particular training protocol are not well understood. We tested the hypothesis that the efficacy of a protocol is determined in part by interactions among biochemical cascades that underlie learning and memory. Previous findings suggest that the protein kinase A (PKA) and extracellular signal-regulated kinase (ERK) cascades are necessary to induce long-term synaptic facilitation (LTF) in Aplysia, a neuronal correlate of memory. We developed a computational model of the PKA and ERK cascades and used it to identify a training protocol that maximized PKA and ERK interactions. In vitro studies confirmed that the protocol enhanced LTF. Moreover, the protocol enhanced the levels of phosphorylation of the transcription factor CREB1. Behavioral training confirmed that long-term memory also was enhanced by the protocol. These results illustrate the feasibility of using computational models to design training protocols that improve memory.
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Jhala S, Tamvacakis AN, Katz PS. Toward locating the source of serotonergic axons in the tail nerve of Aplysia. INVERTEBRATE NEUROSCIENCE 2011; 11:91-6. [PMID: 21877137 DOI: 10.1007/s10158-011-0121-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 08/15/2011] [Indexed: 11/30/2022]
Abstract
Stimulation of the tail nerve (pedal nerve 9, p9) of the mollusk, Aplysia californica, causes release of serotonin (5-HT), which mediates sensitization of withdrawal responses. There are about 35 serotonin-immunoreactive (5-HT-ir) axons in p9, yet the cell bodies of these axons have not been located. Backfills of p9 were combined with 5-HT immunohistochemistry to locate the cell bodies of 5-HT-ir neurons with axons in p9. About 100 neurons had axons in p9. Only about ten neurons, however, were both backfilled and 5-HT-ir. These double-labeled neurons were all located in the pedal ganglion associated with p9, which had a total of approximately 42 5-HT-ir somata. The discrepancy between the number of 5-HT-ir axons and double-labeled cell bodies is not likely due to neurons having multiple axons in the nerve; intracellular fills suggest that these neurons do not branch before entering p9. Additionally, no evidence was found for peripheral 5-HT-ir cell bodies that project axons centrally through p9. Thus, approximately 70% of the neurons that give rise to the 5-HT-ir axons in tail nerve are unaccounted for, but likely to reside in the pedal ganglion.
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Affiliation(s)
- Sagar Jhala
- Neuroscience Institute, Georgia State University, P.O. Box 5030, Atlanta, GA 30302, USA
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