451
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Aberrant learning and memory in addiction. Neurobiol Learn Mem 2011; 96:609-23. [PMID: 21376820 DOI: 10.1016/j.nlm.2011.02.014] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 02/01/2011] [Accepted: 02/22/2011] [Indexed: 12/26/2022]
Abstract
Over the past several years, drug addiction has increasingly been accepted to be a disease of the brain as opposed to simply being due to a lack of willpower or personality flaw. Exposure to addictive substances has been shown to create enduring changes in brain structure and function that are thought to underlie the transition to addiction. Specific genetic and environmental vulnerability factors also influence the impact of drugs of abuse on the brain and can enhance the likelihood of becoming an addict. Long-lasting alterations in brain function have been found in neural circuits that are known to be responsible for normal appetitive learning and memory processes and it has been hypothesized that drugs of abuse enhance positive learning and memory about the drug while inhibiting learning about the negative consequences of drug use. Therefore, the addict's behavior becomes increasingly directed towards obtaining and using drugs of abuse, while at the same time developing a poorer ability to stop using, even when the drug is less rewarding or interferes with functioning in other facets of life. In this review we will discuss the clinical evidence that addicted individuals have altered learning and memory and describe the possible neural substrates of this dysfunction. In addition, we will explore the pre-clinical evidence that drugs of abuse cause a progressive disorder of learning and memory, review the molecular and neurobiological changes that may underlie this disorder, determine the genetic and environmental factors that may increase vulnerability to addiction, and suggest potential strategies for treating addiction through manipulations of learning and memory.
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452
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Abstract
The electrophysiological properties of the sleeping brain profoundly influence memory function in various species, yet the molecular nature by which sleep and memory interact remains unclear. We summarize work that has established the cAMP-PKA-CREB intracellular signaling pathway as a major mechanism involved in the wakeful consolidation of memory in many organisms while highlighting newer evidence that this pathway has a role in sleep regulation, sleep deprivation and potentially sleep-memory interactions. We explore the possibility that sleep might influence memory processing by reactivating the same molecular cascades first recruited during learning during a sort of "molecular replay". Lastly, we discuss how new approaches together with established techniques will aid in our understanding of the nature of sleep-memory interactions.
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Affiliation(s)
- Pepe J Hernandez
- Department of Biology, University of Pennsylvania, Philadelphia, PA
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453
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Dębiec J, Bush DEA, LeDoux JE. Noradrenergic enhancement of reconsolidation in the amygdala impairs extinction of conditioned fear in rats--a possible mechanism for the persistence of traumatic memories in PTSD. Depress Anxiety 2011; 28:186-93. [PMID: 21394851 PMCID: PMC3590026 DOI: 10.1002/da.20803] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Posttraumatic stress disorder (PTSD) is associated with enhanced noradrenergic activity. Animal and human studies demonstrate that noradrenergic stimulation augments consolidation of fear learning. Retrieval of well-established memories by presenting a learned fear cue triggers reconsolidation processes during which memories may be updated, weakened, or strengthened. We previously reported that noradrenergic blockade in the rat amygdala impairs reconsolidation of fear memories. Here we investigated the effects of noradrenergic enhancement on reconsolidation of learned fear. METHODS Using auditory fear conditioning in rats, we tested the effects of postretrieval intraamygdala infusion of the β-adrenergic receptor agonist isoproterenol or the antagonist propranolol on conditioned fear in the amygdala. RESULTS A single intraamygdala infusion of isoproterenol following a retrieval of a well-consolidated memory enhanced fear memory elicited by the learned fear stimulus and impaired extinction of this memory 48 hr later. Intraamygdala infusion of the β-adrenergic receptor antagonist propranolol following a consecutive retrieval trial blocked the enhancing effects of isoproterenol on fear memory. CONCLUSIONS Postretrieval β-adrenergic stimulation in the amygdala enhances reconsolidation of fear memories, making them resistant to extinction. Noradrenergic augmentation during retrieval of fear memories may thus contribute to persistence and severity of traumatic memories. Reconsolidation may be a useful tool in understanding the pathology of PTSD and may thus help in developing new and in modifying existing treatments of traumatic memories.
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Affiliation(s)
- Jacek Dębiec
- W.M. Keck Foundation Laboratory of Neurobiology, Center for Neural Science, New York University, New York, NY, USA.
| | - David E. A. Bush
- W.M. Keck Foundation Laboratory of Neurobiology, Center for Neural Science, New York University, New York, NY
| | - Joseph E. LeDoux
- W.M. Keck Foundation Laboratory of Neurobiology, Center for Neural Science, New York University, New York, NY
,Department of Psychology, New York University, New York, NY
,Emotional Brain Institute, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY
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454
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Tramoni E, Felician O, Barbeau EJ, Guedj E, Guye M, Bartolomei F, Ceccaldi M. Long-term consolidation of declarative memory: insight from temporal lobe epilepsy. Brain 2011; 134:816-31. [DOI: 10.1093/brain/awr002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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455
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Boccia MM, Blake MG, Krawczyk MC, Baratti CM. Sildenafil, a selective phosphodiesterase type 5 inhibitor, enhances memory reconsolidation of an inhibitory avoidance task in mice. Behav Brain Res 2011; 220:319-24. [PMID: 21333692 DOI: 10.1016/j.bbr.2011.02.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 12/25/2022]
Abstract
Intracellular levels of the second messengers cAMP and cGMP are maintained through a balance between production, carried out by adenyl cyclase (AC) and guanylyl cyclase (GC), and degradation, carried out by phosphodiesterases (PDEs). Recently, PDEs have gained increased attention as potential new targets for cognition enhancement, with particular reference to phosphodiesterase type 5 (PDE5A). It is accepted that once consolidation is completed memory becomes permanent, but it has also been suggested that reactivation (memory retrieval) of the original memory makes it sensitive to the same treatments that affect memory consolidation when given after training. This new period of sensitivity coined the term reconsolidation. Sildenafil (1, 3, and 10mg/kg, ip), a cGMP-PDE5 inhibitor, facilitated retention performance of a one-trial step-through inhibitory avoidance task, when administered to CF-1 male mice immediately after retrieval. The effects of sildenafil (1mg/kg, ip) were time-dependent, long-lasting and inversely correlated with memory age. The administration of sildenafil (1mg/kg, ip) 30 min prior to the 2nd retention test did not affect retention of mice given post-retrieval injections of either vehicle or sildenafil (1mg/kg, ip). Finally, an enhancement of retention was also observed in CF-1 female mice receiving sildenafil (1mg/kg, ip) immediately, but not 180 min after retrieval. In the present paper we reported for the first time that systemic administration of sildenafil after memory reactivation enhances retention performance of the original learning. Our results indirectly point out cGMP, a component of the NO/cGMP/PKG pathway, as a necessary factor for memory reconsolidation.
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Affiliation(s)
- M M Boccia
- Laboratorio de Neurofarmacología de los Procesos de Memoria, Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina.
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456
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Orsi L, D'Agata F, Caroppo P, Franco A, Caglio MM, Avidano F, Manzone C, Mortara P. Neuropsychological picture of 33 spinocerebellar ataxia cases. J Clin Exp Neuropsychol 2011; 33:315-25. [DOI: 10.1080/13803395.2010.518139] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Laura Orsi
- a Department of Neuroscience , AOU San Giovanni Battista , Turin, Italy
- c Neurological Clinic II, AOU San Giovanni Battista , Turin, Italy
- e Center for Spinocerebellar Ataxia Diseases, AOU San Giovanni Battista , Turin, Italy
| | - Federico D'Agata
- a Department of Neuroscience , AOU San Giovanni Battista , Turin, Italy
- f Laboratory of Neuropsychology, AOU San Giovanni Battista , Turin, Italy
- g Department of Psychology , University of Turin , Turin, Italy
| | - Paola Caroppo
- a Department of Neuroscience , AOU San Giovanni Battista , Turin, Italy
- b Neurological Clinic I, AOU San Giovanni Battista , Turin, Italy
- e Center for Spinocerebellar Ataxia Diseases, AOU San Giovanni Battista , Turin, Italy
- f Laboratory of Neuropsychology, AOU San Giovanni Battista , Turin, Italy
| | - Alessandra Franco
- c Neurological Clinic II, AOU San Giovanni Battista , Turin, Italy
- d Neurological Division ASL 4, Ciriè Hospital , Ciriè, Italy
| | | | - Federica Avidano
- f Laboratory of Neuropsychology, AOU San Giovanni Battista , Turin, Italy
| | - Cristina Manzone
- f Laboratory of Neuropsychology, AOU San Giovanni Battista , Turin, Italy
| | - Paolo Mortara
- a Department of Neuroscience , AOU San Giovanni Battista , Turin, Italy
- b Neurological Clinic I, AOU San Giovanni Battista , Turin, Italy
- f Laboratory of Neuropsychology, AOU San Giovanni Battista , Turin, Italy
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457
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Storozheva ZI, Solntseva SV, Nikitin VP, Proshin AT, Sherstnev VV. Irreversible Amnesia in Rats and Edible Snails under Conditions of Associative Memory Reconsolidation Disturbance Caused by NMDA-Glutamate Receptor Antagonist. Bull Exp Biol Med 2011; 150:286-90. [DOI: 10.1007/s10517-011-1124-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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458
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The use of cognitive enhancers in animal models of fear extinction. Pharmacol Biochem Behav 2011; 99:217-28. [PMID: 21256147 DOI: 10.1016/j.pbb.2011.01.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2010] [Revised: 12/25/2010] [Accepted: 01/11/2011] [Indexed: 11/23/2022]
Abstract
In anxiety disorders, such as posttraumatic stress disorders and phobias, classical conditioning pairs natural (unconditioned) fear-eliciting stimuli with contextual or discrete cues resulting in enduring fear responses to multiple stimuli. Extinction is an active learning process that results in a reduction of conditioned fear responses after conditioned stimuli are no longer paired with unconditioned stimuli. Fear extinction often produces incomplete effects and this highlights the relative permanence of bonds between conditioned stimuli and conditioned fear responses. The animal research literature is rich in its demonstration of cognitive enhancing agents that alter fear extinction. This review specifically examines the fear extinguishing effects of cognitive enhancers that act on gamma-aminobutyric acid (GABA), glutamatergic, cholinergic, adrenergic, dopaminergic, and cannabinoid signaling pathways. It also examines the effects of compounds that alter epigenetic and neurotrophic mechanisms in fear extinction. Of these cognitive enhancers, glutamatergic N-methyl d-aspartate (NMDA) receptor agonists, such as D-cycloserine, have enhanced fear extinction in a context-, dose- and time-dependent manner. Agents that function as glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor agonists, alpha2-adrenergic receptor antagonists (such as yohimbine), neurotrophic factors (brain derived neurotrophic factor or BDNF) and histone deacetylase inhibitors (valproate and sodium butyrate) also improve fear extinction in animals. However, some have anxiogenic effects and their contextual and temporal effects need to be more reliably demonstrated. Various cognitive enhancers produce changes in cortico-amygdala synaptic plasticity through multiple mechanisms and these neural changes enhance fear extinction. We need to better define the changes in neural plasticity produced by these agents in order to develop more effective compounds. In the clinical setting, such use of effective cognitive enhancers with cue exposure therapy, using compounds derived from animal model studies, provides great hope for the future treatment of anxiety disorders.
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459
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Abstract
Drug addiction is a syndrome of impaired response inhibition and salience attribution, which involves a complex neurocircuitry underlying drug reinforcement, drug craving, and compulsive drug-seeking and drug-taking behaviors despite adverse consequences. The concept of disease stages with transitions from acute rewarding effects to early- and end-stage addiction has had an important impact on the design of nonclinical animal models. This chapter reviews the main advances in nonclinical paradigms that aim to at model (1) positive and negative reinforcing effects of addictive drugs; (2) relapse to drug-seeking behavior; (3) reconsolidation of drug cue memories, and (4) compulsive/impulsive drug intake. In addition, recent small animal neuroimaging studies and invertebrate models will be briefly discussed (see also Bifone and Gozzi, Animal models of ADHD, 2011). Continuous improvement in modeling drug intake, craving, withdrawal symptoms, relapse, and comorbid psychiatric associations is a necessary step to better understand the etiology of the disease and to ultimately foster the discovery, validation and optimization of new efficacious pharmacotherapeutic approaches. The modeling of specific subprocesses or constructs that address clinically defined criteria will ultimately increase our understanding of the disease as a whole. Future research will have to address the questions of whether some of these constructs can be reliably used as outcome measures to assess the effects of a treatment in clinical settings, whether changes in those measures can be a target of therapeutic efforts, and whether they relate to biological markers of traits such as impulsivity, which contribute to increased drug-seeking and may predict binge-like patterns of drug intake.
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Affiliation(s)
- Christian Heidbreder
- Reckitt Benckiser Pharmaceuticals Inc., 10710 Midlothian Turnpike, Suite 430, Richmond, VA, 23235, USA,
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460
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Treatment of addiction and anxiety using extinction approaches: Neural mechanisms and their treatment implications. Pharmacol Biochem Behav 2011; 97:619-25. [DOI: 10.1016/j.pbb.2010.08.004] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2010] [Revised: 08/05/2010] [Accepted: 08/12/2010] [Indexed: 12/26/2022]
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461
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Abstract
Activins, which are members of the TGF-β superfamily, were initially isolated from gonads and served as modulators of follicle-stimulating hormone secretion. Activins regulate various biological functions, including induction of the dorsal mesoderm, craniofacial development, and differentiation of numerous cell types. Activin receptors are highly expressed in neuronal cells, and activin mRNA expression is upregulated by neuronal activity. Activins also exhibit neuroprotective action during excitotoxic brain injury. However, very little is known about the functional roles of activins in the brain. We recently generated various types of transgenic mice, demonstrating that activins regulate spine formation, behavioral activity, anxiety, adult neurogenesis, late-phase long-term potentiation, and maintenance of long-term memory. The present chapter describes recent progress in the study of the role of activin in the brain.
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Affiliation(s)
- Hiroshi Ageta
- Division for Therapies against Intractable Diseases, Institute for Comprehensive Medical Science (ICMS), Fujita Health University, Toyoake, Aichi, Japan
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462
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Maddox SA, Monsey MS, Schafe GE. Early growth response gene 1 (Egr-1) is required for new and reactivated fear memories in the lateral amygdala. Learn Mem 2011; 18:24-38. [PMID: 21177377 PMCID: PMC3023969 DOI: 10.1101/lm.1980211] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 10/13/2010] [Indexed: 01/16/2023]
Abstract
The immediate-early gene early growth response gene-1 (EGR-1, zif-268) has been extensively studied in synaptic plasticity and memory formation in a variety of memory systems. However, a convincing role for EGR-1 in amygdala-dependent memory consolidation processes has yet to emerge. In the present study, we have examined the role of EGR-1 in the consolidation and reconsolidation of amygdala-dependent auditory Pavlovian fear conditioning. In our first series of experiments, we show that EGR-1 is regulated following auditory fear conditioning in the lateral nucleus of the amygdala (LA). Next, we use antisense oligodeoxynucleotide (ODN) knockdown of EGR-1 in the LA to show that training-induced expression of EGR-1 is required for memory consolidation of auditory fear conditioning; that is, long-term memory (LTM) is significantly impaired while acquisition and short-term memory (STM) are intact. In a second set of experiments, we show that EGR-1 is regulated in the LA by retrieval of an auditory fear memory. We then show that retrieval-induced expression of EGR-1 in the LA is required for memory reconsolidation of auditory fear conditioning; that is, post-retrieval (PR)-LTM is significantly impaired while memory retrieval and PR-STM are intact. Additional experiments show these effects to be restricted to the LA, to be temporally graded, and unlikely to be due to nonspecific toxicity within the LA. Collectively, our findings strongly implicate a role for EGR-1 in both the initial consolidation and in the reconsolidation of auditory fear memories in the LA.
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Affiliation(s)
- Stephanie A. Maddox
- Department of Psychology, Yale University, New Haven, Connecticut 06520, USA
| | - Melissa S. Monsey
- Department of Psychology, Yale University, New Haven, Connecticut 06520, USA
| | - Glenn E. Schafe
- Department of Psychology, Yale University, New Haven, Connecticut 06520, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, Connecticut 06520, USA
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463
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Ogasawara H, Kawato M. The protein kinase Mζ network as a bistable switch to store neuronal memory. BMC SYSTEMS BIOLOGY 2010; 4:181. [PMID: 21194445 PMCID: PMC3022653 DOI: 10.1186/1752-0509-4-181] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2010] [Accepted: 12/31/2010] [Indexed: 11/10/2022]
Abstract
Background Protein kinase Mζ (PKMζ), the brain-specific, atypical protein kinase C isoform, plays a key role in long-term maintenance of memory. This molecule is essential for long-term potentiation of the neuron and various modalities of learning such as spatial memory and fear conditioning. It is unknown, however, how PKMζ stores information for long periods of time despite molecular turnover. Results We hypothesized that PKMζ forms a bistable switch because it appears to constitute a positive feedback loop (PKMζ induces its local synthesis) part of which is ultrasensitive (PKMζ stimulates its synthesis through dual pathways). To examine this hypothesis, we modeled the biochemical network of PKMζ with realistic kinetic parameters. Bifurcation analyses of the model showed that the system maintains either the up state or the down state according to previous inputs. Furthermore, the model was able to reproduce a variety of previous experimental results regarding synaptic plasticity and learning, which suggested that it captures the essential mechanism for neuronal memory. We proposed in vitro and in vivo experiments that would critically examine the validity of the model and illuminate the pivotal role of PKMζ in synaptic plasticity and learning. Conclusions This study revealed bistability of the PKMζ network and supported its pivotal role in long-term storage of memory.
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Affiliation(s)
- Hideaki Ogasawara
- National Institute of Information and Communications Technology, 2-2-2, Hikaridai, Seika, Kyoto 619-0288, Japan.
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464
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Sara SJ. Reactivation, retrieval, replay and reconsolidation in and out of sleep: connecting the dots. Front Behav Neurosci 2010; 4:185. [PMID: 21179586 PMCID: PMC3004439 DOI: 10.3389/fnbeh.2010.00185] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Accepted: 11/24/2010] [Indexed: 01/18/2023] Open
Abstract
The neurobiology of memory has taken on a new look over the past decade. Re-discovery of cue-dependent amnesia, wide availability of functional imaging tools and increased dialog among clinicians, cognitive psychologists, behavioral neuroscientists, and neurobiologists have provided impetus for the search for new paradigms for the study of memory. Memory is increasingly viewed as an open-ended process, with retrieval being recognized as an intricate part of the encoding process. New memories are always made on the background of past experience, so that every consolidation is, in fact reconsolidation, serving to update and strengthen memories after retrieval. Spontaneous reactivation of memory circuits occurs during sleep and there is converging evidence from rodent and human studies that this is an important part of the extended off-line memory processing. The noradrenergic neuromodulatory system is engaged at retrieval, facilitating recall. The noradrenergic system is also activated during sleep after learning and noradrenergic neurons fire in concert with cortical oscillations that are associated with reactivation of memory circuits. We suggest that the noradrenergic system and perhaps other neuromodulatory systems, may be a key to linking off-line memory reactivation, retrieval, and memory reconsolidation processes at both synaptic and systems levels, in and out of sleep.
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Affiliation(s)
- Susan J Sara
- Laboratoire de Physiologie de la Perception et de l'Action, UMR 7152, Collège de France, Centre National de la Recherche Scientifique Paris, France
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465
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Boccia M, Blake M, Krawczyk M, Baratti C. Hippocampal alpha7 nicotinic receptors modulate memory reconsolidation of an inhibitory avoidance task in mice. Neuroscience 2010; 171:531-43. [DOI: 10.1016/j.neuroscience.2010.08.027] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/12/2010] [Accepted: 08/13/2010] [Indexed: 01/06/2023]
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466
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Wouda JA, Diergaarde L, Riga D, van Mourik Y, Schoffelmeer ANM, De Vries TJ. Disruption of Long-Term Alcohol-Related Memory Reconsolidation: Role of β-Adrenoceptors and NMDA Receptors. Front Behav Neurosci 2010; 4:179. [PMID: 21152256 PMCID: PMC2998860 DOI: 10.3389/fnbeh.2010.00179] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 11/09/2010] [Indexed: 11/13/2022] Open
Abstract
Disrupting reconsolidation of drug-related memories may be effective in reducing the incidence of relapse. In the current study we examine whether alcohol-related memories are prone to disruption by the β-adrenergic receptor antagonist propranolol (10 mg/kg) and the NMDA receptor antagonist MK801 (0.1 mg/kg) following their reactivation. In operant chambers, male Wistar rats were trained to self-administer a 12% alcohol solution. After 3 weeks of abstinence, the animals were placed in the self-administration cages and were re-exposed to the alcohol-associated cues for a 20-min retrieval period, immediately followed by a systemic injection of either propranolol, MK801 or saline. Rats were tested for cue-induced alcohol seeking on the following day. Retrieval session, injection and test were repeated on two further occasions at weekly intervals. Both propranolol and MK801 administration upon reactivation did not reduce alcohol seeking after the first reactivation test. However, a significant reduction of alcohol seeking was observed over three post-training tests in propranolol treated animals, and MK801 treated animals showed a strong tendency toward reduced alcohol seeking (p = 0.06). Our data indicate that reconsolidation of alcohol-related memories can be disrupted after a long post-training interval and that particularly β-adrenergic receptors may represent novel targets for pharmacotherapy of alcoholism, in combination with cue-exposure therapies.
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Affiliation(s)
- Jelte A Wouda
- Department of Anatomy and Neurosciences, VU University Medical Center, Neuroscience Campus Amsterdam Amsterdam, Netherlands
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467
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Davis S, Renaudineau S, Poirier R, Poucet B, Save E, Laroche S. The formation and stability of recognition memory: what happens upon recall? Front Behav Neurosci 2010; 4:177. [PMID: 21120149 PMCID: PMC2992451 DOI: 10.3389/fnbeh.2010.00177] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 10/29/2010] [Indexed: 12/13/2022] Open
Abstract
The idea that an already consolidated memory can become destabilized after recall and requires a process of reconsolidation to maintain it for subsequent use has gained much credence over the past decade. Experimental studies in rodents have shown pharmacological, genetic, or injurious manipulation at the time of memory reactivation can disrupt the already consolidated memory. Despite the force of experimental data showing this phenomenon, a number of questions have remained unanswered and no consensus has emerged as to the conditions under which a memory can be disrupted following reactivation. To date most rodent studies of reconsolidation are based on negatively reinforced memories, in particular fear-associated memories, while the storage and stability of forms of memory that do not rely on explicit reinforcement have been less often studied. In this review, we focus on recognition memory, a paradigm widely used in humans to probe declarative memory. We briefly outline recent advances in our understanding of the processes and brain circuits involved in recognition memory and review the evidence that recognition memory can undergo reconsolidation upon reactivation. We also review recent findings suggesting that some molecular mechanisms underlying consolidation of recognition memory are similarly recruited after recall to ensure memory stability, while others are more specifically engaged in consolidation or reconsolidation. Finally, we provide novel data on the role of Rsk2, a mental retardation gene, and of the transcription factor zif268/egr1 in reconsolidation of object-location memory, and offer suggestions as to how assessing the activation of certain molecular mechanisms following recall in recognition memory may help understand the relative importance of different aspects of remodeling or updating long-lasting memories.
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Affiliation(s)
- Sabrina Davis
- Centre de Neurosciences Paris-Sud, UMR 8195, Univ Paris-Sud Orsay, France
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468
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Barnes P, Kirtley A, Thomas KL. Quantitatively and qualitatively different cellular processes are engaged in CA1 during the consolidation and reconsolidation of contextual fear memory. Hippocampus 2010; 22:149-71. [PMID: 21080409 DOI: 10.1002/hipo.20879] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2010] [Indexed: 01/12/2023]
Abstract
Whether the consolidation and reconsolidation long-term memory relies on qualitatively different molecular and cellular processes is controversial. Using a novel experimental strategy of combining intrahippocampal antisense oligodeoxynucleotides targeting BDNF or zif268 to the block consolidation or reconsolidation of contextual fear memory respectively, and Affymetrix microarray technology, we identified a comprehensive list of nonoverlapping candidate genes regulated in CA1 during the initial stages consolidation and reconsolidation. Using RT-qPCR in subsequent validation experiments, we estimated that over 80% of the candidates reflect gene transcripts truly regulated following the acquisition or retrieval of contextual fear memory. Statistical and over-representation bioinformatics analyses revealed that cellular processes and signaling mechanisms were differentially regulated during consolidation and reconsolidation, particularly those associated with pro-inflammatory cytokine signaling. This predicts that the two mnemonic processes are qualitatively as well as quantitatively distinct. This experimental strategy was further validated because the cytokine interleukin 1 (IL-1) was reciprocally regulated in CA1 after contextual fear conditioning and fear memory retrieval, and we showed for the first time that that IL-1 receptor mediated signaling in the hippocampus was necessary for reconsolidation.
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Affiliation(s)
- Philip Barnes
- Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff, United Kingdom
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469
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Lee JLC. Memory reconsolidation mediates the updating of hippocampal memory content. Front Behav Neurosci 2010; 4:168. [PMID: 21120142 PMCID: PMC2991235 DOI: 10.3389/fnbeh.2010.00168] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 10/06/2010] [Indexed: 11/13/2022] Open
Abstract
The retrieval or reactivation of a memory places it into a labile state, requiring a process of reconsolidation to restabilize it. This retrieval-induced plasticity is a potential mechanism for the modification of the existing memory. Following previous data supportive of a functional role for memory reconsolidation in the modification of memory strength, here I show that hippocampal memory reconsolidation also supports the updating of contextual memory content. Using a procedure that separates the learning of pure context from footshock-motivated contextual fear learning, I demonstrate doubly dissociable hippocampal mechanisms of initial context learning and subsequent updating of the neutral contextual representation to incorporate the footshock. Contextual memory consolidation was dependent upon BDNF expression in the dorsal hippocampus, whereas the footshock modification of the contextual representation required the expression of Zif268. These mechanisms match those previously shown to be selectively involved in hippocampal memory consolidation and reconsolidation, respectively. Moreover, memory reactivation is a necessary step in modifying memory content, as inhibition of hippocampal synaptic protein degradation also prevented the footshock-mediated memory modification. Finally, dorsal hippocampal knockdown of Zif268 impaired the reconsolidation of the pure contextual memory only under conditions of weak context memory training, as well as failing to disrupt contextual freezing when a strong contextual fear memory is reactivated by further conditioning. Therefore, an adaptive function of the reactivation and reconsolidation process is to enable the updating of memory content.
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470
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Angiotensin modulates long-term memory expression but not long-term memory storage in the crab Chasmagnathus. Neurobiol Learn Mem 2010; 94:509-20. [DOI: 10.1016/j.nlm.2010.09.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 08/30/2010] [Accepted: 09/01/2010] [Indexed: 12/20/2022]
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471
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Machado I, González P, Schiöth HB, Lasaga M, Scimonelli TN. α-Melanocyte-stimulating hormone (α-MSH) reverses impairment of memory reconsolidation induced by interleukin-1 beta (IL-1 beta) hippocampal infusions. Peptides 2010; 31:2141-4. [PMID: 20688120 DOI: 10.1016/j.peptides.2010.07.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Revised: 07/15/2010] [Accepted: 07/15/2010] [Indexed: 12/14/2022]
Abstract
Interleukin-1 beta (IL-1β) significantly influences cognitive processes. Treatments which raise the level of IL-1β in the brain impair memory consolidation in contextual fear conditioning. However, the effect of IL-1β on memory reconsolidation has not yet been established. The melanocortin α-melanocyte-stimulating hormone (α-MSH) exerts potent anti-inflammatory actions by antagonizing the effect of proinflammatory cytokines. Five subtypes of melanocortin receptors (MC1R-MC5R) have been identified, of which MC3R and MC4R are predominant in the central nervous system. The present experiments show that the injection of IL-1β (5 ng/0.25 μl) in dorsal hippocampus up to 30 min after re-exposition to the context decreases freezing during the contextual fear test. Impairment of memory reconsolidation was reversed by treatment with α-MSH (0.05 μg/0.25 μl). Administration of the MC4 receptor antagonist HS014 (0.5 μg/0.25 μl) blocked the effect of α-MSH. These results suggest that IL-1β may influence memory reconsolidation and that activation of central MC4R could lead to improve cognitive performance.
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Affiliation(s)
- Ivana Machado
- IFEC CONICET Departamento Farmacología, Facultad de Ciencias Químicas, UNC, Córdoba, Argentina
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472
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Role of beta-adrenergic receptors in the ventromedial prefrontal cortex during contextual fear extinction in rats. Neurobiol Learn Mem 2010; 94:318-28. [DOI: 10.1016/j.nlm.2010.07.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 07/11/2010] [Accepted: 07/20/2010] [Indexed: 11/19/2022]
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473
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Solntseva SV, Nikitin VP. Effects of agonists of NMDA and serotonin receptors at different stages of amnesia caused by impairment of long-term memory reconsolidation. NEUROCHEM J+ 2010. [DOI: 10.1134/s1819712410030050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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474
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Basolateral amygdala cdk5 activity mediates consolidation and reconsolidation of memories for cocaine cues. J Neurosci 2010; 30:10351-9. [PMID: 20685978 DOI: 10.1523/jneurosci.2112-10.2010] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Cocaine use and relapse involves learned associations between cocaine-associated environmental contexts and discrete stimuli and cocaine effects. Initially, these contextual and discrete cues undergo memory consolidation after being paired with cocaine exposure. During abstinence, cocaine cue memories can undergo memory reconsolidation after cue exposure without the drug. We used a conditioned place preference (CPP) procedure in rats to study the role of neuronal protein kinase cyclin-dependent kinase 5 (Cdk5) in consolidation and reconsolidation of cocaine cue memories. We found that the expression of cocaine CPP in drug-free tests 1 d after CPP training (four pairings of 10 mg/kg cocaine with one context and four pairings of saline with a different context) increased Cdk5 activity, and levels of the Cdk5 activator p35 in basolateral but not central amygdala. We also found that basolateral (but not central) amygdala injections of the Cdk5 inhibitor beta-butyrolactone (100 ng/side) immediately (but not 6 h) after cocaine-context pairings during training prevented subsequent cocaine CPP expression. After training, acute basolateral (but not central) amygdala beta-butyrolactone injections immediately before testing prevented the expression of cocaine CPP; this effect was also observed on a second test performed 1 d later, suggesting an effect on reconsolidation of cocaine cue memories. In support, basolateral beta-butyrolactone injections, given immediately (but not 6 h) after a single exposure to the cocaine-paired context, prevented cocaine CPP expression 1 and 14 d after the injections. Results indicate that basolateral amygdala Cdk5 activity is critical for consolidation and reconsolidation of the memories of cocaine-associated environmental cues.
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475
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Robinson MJF, Ross EC, Franklin KBJ. The effect of propranolol dose and novelty of the reactivation procedure on the reconsolidation of a morphine place preference. Behav Brain Res 2010; 216:281-4. [PMID: 20713093 DOI: 10.1016/j.bbr.2010.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 07/20/2010] [Accepted: 08/06/2010] [Indexed: 10/19/2022]
Abstract
Previously consolidated memories may become labile when they are reactivated and require reconsolidation. It has been suggested that when novel information is present at the time of memory reactivation reconsolidation is engaged but when no new information is present, reconsolidation may not occur, and extinction may be the dominant process instead. To test this idea we trained rats to associate a context with the rewarding properties of morphine (5 mg/kg, sc) over four conditioning pairings. Following training, animals were reactivated by a 30-min test session, once a day for 3 days. Rats were injected with the amnestic drug propranolol (10 or 40 mg/kg, sc) following reactivation either on the first or on the second day. They received saline on the alternate day. Propranolol disrupted reconsolidation for a conditioned place preference only when given on the first reactivation day, and this effect was more robust following the higher dose of propranolol. In contrast, animals given propranolol on the second reactivation day still displayed a preference for the morphine-paired context on the final test day. These results support the view that for memory to return to a labile state, the situation that evokes reactivation needs to be novel in some way. If the reactivation situation is familiar, reconsolidation may not occur.
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Affiliation(s)
- M J F Robinson
- Department of Psychology, McGill University, 1205 Dr. Penfield Ave., Montreal, Quebec, Canada H3A 1B1
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476
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Romero-Granados R, Fontán-Lozano A, Delgado-García JM, Carrión AM. From learning to forgetting: behavioral, circuitry, and molecular properties define the different functional states of the recognition memory trace. Hippocampus 2010; 20:584-95. [PMID: 19603520 DOI: 10.1002/hipo.20669] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neuropsychological analyses of amnesic patients, as well as lesion experiments, indicate that the temporal lobe is essential for the encoding, storage, and expression of object recognition memory (ORM). However, temporal lobe structures directly involved in the consolidation and reconsolidation of these memories are not yet well-defined. We report here that systemic administration of a protein synthesis inhibitor before or up to 4 h after training or reactivation sessions impairs consolidation and reconsolidation of ORM, without affecting short-term memory. We have also observed that ORM reconsolidation is sensitive to protein synthesis inhibition, independently of the ORM trace age. Using bdnf and egr-1 gene expression analysis, we defined temporal lobe areas related to consolidation and reconsolidation of ORM. Training and reactivation 21 days after ORM acquisition sessions provoked changes in bdnf mRNA in somatosensory, perirhinal, and hippocampal cortices. Reactivation 2 days after the training session elicited changes in bdnf and egr-1 mRNA in entorhinal and prefrontal cortices, while reactivation 9 days post-training provoked an increase in egr-1 transcription in somatosensory and entorhinal cortices. The differences in activated circuits and in the capacity to recall the memory trace after 9 or 21 days post-training suggest that memory trace suffers functional changes in this period of time. All these results indicate that the functional state of the recognition memory trace, from acquisition to forgetting, can be specifically defined by behavioral, circuitry, and molecular properties.
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Affiliation(s)
- Rocío Romero-Granados
- División de Neurociencias, Universidad Pablo de Olavide de Sevilla, Carretera de Utrera, Km. 1, 41013-Sevilla, Spain
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477
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Impairment of contextual conditioned fear extinction after microinjection of alpha-1-adrenergic blocker prazosin into the medial prefrontal cortex. Behav Brain Res 2010; 211:89-95. [DOI: 10.1016/j.bbr.2010.03.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 03/01/2010] [Accepted: 03/05/2010] [Indexed: 11/22/2022]
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478
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Kozyrev SA, Nikitin VP. Neuronal Mechanisms of Reconsolidation of an Associative Aversive Skill to Food in the Common Snail. ACTA ACUST UNITED AC 2010; 40:715-22. [DOI: 10.1007/s11055-010-9317-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Indexed: 11/24/2022]
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479
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Dissociating response systems: Erasing fear from memory. Neurobiol Learn Mem 2010; 94:30-41. [DOI: 10.1016/j.nlm.2010.03.004] [Citation(s) in RCA: 222] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 03/05/2010] [Accepted: 03/25/2010] [Indexed: 11/22/2022]
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480
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Makkar SR, Zhang SQ, Cranney J. Behavioral and neural analysis of GABA in the acquisition, consolidation, reconsolidation, and extinction of fear memory. Neuropsychopharmacology 2010; 35:1625-52. [PMID: 20410874 PMCID: PMC3055480 DOI: 10.1038/npp.2010.53] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 03/17/2010] [Accepted: 03/22/2010] [Indexed: 11/09/2022]
Abstract
The current review systematically documents the role of gamma-amino-butyric acid (GABA) in different aspects of fear memory-acquisition and consolidation, reconsolidation, and extinction, and attempts to resolve apparent contradictions in the data in order to identify the function of GABA(A) receptors in fear memory. First, numerous studies have shown that pre- and post-training administration of drugs that facilitate GABAergic transmission disrupt the initial formation of fear memories, indicating a role for GABA(A) receptors, possibly within the amygdala and hippocampus, in the acquisition and consolidation of fear memories. Similarly, recent evidence indicates that these drugs are also detrimental to the restorage of fear memories after their reactivation. This suggests a role for GABA(A) receptors in the reconsolidation of fear memories, although the precise neural circuits are yet to be identified. Finally, research regarding the role of GABA in extinction has shown that GABAergic transmission is also disruptive to the formation of newly acquired extinction memories. We argue that contradictions to these patterns are the result of variations in (a) the location of drug infusion, (b) the dosage of the drug and/or (c) the time point of drug administration. The question of whether these GABA-induced memory deficits reflect deficits in retrieval is discussed. Overall, the evidence implies that the processes mediating memory stability consequent to initial fear learning, memory reactivation, and extinction training are dependent on a common mechanism of reduced GABAergic neurotransmission.
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Affiliation(s)
- Steve R Makkar
- School of Psychology, University of New South Wales, Sydney, NSW, Australia
| | - Shirley Q Zhang
- School of Psychology, University of New South Wales, Sydney, NSW, Australia
| | - Jacquelyn Cranney
- School of Psychology, University of New South Wales, Sydney, NSW, Australia
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481
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Yamada D, Wada E, Amano T, Wada K, Sekiguchi M. Lack of neurotensin type 1 receptor facilitates contextual fear memory depending on the memory strength. Pharmacol Biochem Behav 2010; 96:363-9. [PMID: 20600248 DOI: 10.1016/j.pbb.2010.06.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 05/26/2010] [Accepted: 06/11/2010] [Indexed: 12/18/2022]
Abstract
Neurotensin is known to have antipsychotic-like behavioral and neurochemical effects, but its participation in fear memory has not been fully elucidated. Here, we report that a lack of type 1 neurotensin receptor (Ntsr1) increases the behavioral fear response elicited by weak fear memory. Adult Ntsr1-knockout (KO) mice and their wild-type (WT) littermates were compared in contextual fear conditioning. The mice were exposed twice for 3min to the context 24 and 48h after conditioning (first and second exposure, respectively), and freezing response of mice at the exposure was measured to evaluate fear memory. Ntsr1-KO mice showed a higher freezing rate than WT mice at both first and second exposures under the condition where a relatively weak unconditioned stimulus (footshock) was applied and thus elicited a relatively lower freezing rate. The difference in the first exposure between Ntsr1-KO and WT mice disappeared under the condition where a more intense unconditioned stimulus was used. The enhancement of freezing response in Ntsr1-KO mice at second exposure was abolished by propranolol, a beta-adrenergic blocker that suppresses fear memory reconsolidation, and suppressed by MK-801, an NMDA receptor antagonist. These results suggest that Ntsr1 plays inhibitory roles in weak fear memory.
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Affiliation(s)
- Daisuke Yamada
- Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
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482
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Reversible and irreversible stages in the development of amnesia after disruption of the reactivation of associative memory in snails. ACTA ACUST UNITED AC 2010; 40:679-86. [PMID: 20544391 DOI: 10.1007/s11055-010-9311-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Accepted: 10/20/2008] [Indexed: 10/19/2022]
Abstract
Our previous studies on common snails have demonstrated that inhibition of NMDA glutamate receptors during reactivation of a skill consisting of refusal of a defined foodstuff leads to impairment of long-term memory. We report here our studies of the dynamics of the development of amnesia. Snails were trained to refuse a defined foodstuff and were injected 24 h later with the NMDA glutamate receptor antagonist MK-801, and were then presented with the conditioned food stimulus (a reminder). Testing on days 1 and 3 after exposure to MK-801 and the reminder showed gradual decreases in the number of refusals of the conditioned food stimulus. Repeat training of the animals to refuse the same foodstuff performed during these periods led to restoration of the skill seen after the initial training. The number of refusals by snails of the conditioned food stimulus 10 days after MK-801 and the reminder decreased to a minimal level. Repeat training at this time did not lead to the formation of a conditioned reflex to food. Thus, we have provided the first demonstration that impairment of the reactivation of long-term memory induces two stages in the development of amnesia. The first, reversible, stage, which lasted less than 10 days, was characterized by the potential for long-term memory to be restored by repeat training of the snails. The second, irreversible, stage developed 10 days after induction of amnesia and was characterized by disruption of the ability of long-term memory to be restored. These results may have practical value in terms of understanding the mechanisms of acute memory loss due to trauma and neurological diseases.
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483
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Abstract
This paper introduces a new model of associative memory, capable of both binary and continuous-valued inputs. Based on kernel theory, the memory model is on one hand a generalization of Radial Basis Function networks and, on the other, is in feature space, analogous to a Hopfield network. Attractors can be added, deleted, and updated on-line simply, without harming existing memories, and the number of attractors is independent of input dimension. Input vectors do not have to adhere to a fixed or bounded dimensionality; they can increase and decrease it without relearning previous memories. A memory consolidation process enables the network to generalize concepts and form clusters of input data, which outperforms many unsupervised clustering techniques; this process is demonstrated on handwritten digits from MNIST. Another process, reminiscent of memory reconsolidation is introduced, in which existing memories are refreshed and tuned with new inputs; this process is demonstrated on series of morphed faces.
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Affiliation(s)
- Dimitri Nowicki
- Biologically Inspired Neural and Dynamical Systems (BINDS) Lab, Department of Computer Science, University of Massachusetts Amherst, Amherst, Massachusetts, USA.
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484
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Milton AL, Everitt BJ. The psychological and neurochemical mechanisms of drug memory reconsolidation: implications for the treatment of addiction. Eur J Neurosci 2010; 31:2308-19. [PMID: 20497475 DOI: 10.1111/j.1460-9568.2010.07249.x] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Memory reconsolidation is the process by which memories, destabilised at retrieval, require restabilisation to persist in the brain. It has been demonstrated that even old, well-established memories require reconsolidation following retrieval; therefore, memory reconsolidation could potentially be exploited to disrupt, or even erase, aberrant memories that underlie psychiatric disorders, thereby providing a novel therapeutic target. Drug addiction is one such disorder; it is both chronic and relapsing, and one prominent risk factor for a relapse episode is the presentation of environmental cues that have previously been associated with drugs of abuse. This 'cue-induced relapse' can be accounted for in psychological terms by reinforcing memories of the pavlovian association between the cue and the drug, which can thus influence behaviour through at least three psychologically and neurobiologically dissociable mechanisms: conditioned reinforcement, conditioned approach and conditioned motivation. As each of these psychological processes could contribute to the resumption of drug-seeking following abstinence, it is important to develop treatments that can reduce drug-seeking re-established via influences on each or all of these pavlovian processes, in order to minimise the risk of a subsequent relapse. Investigation of the memory reconsolidation mechanisms of the memories underlying conditioned reinforcement, conditioned approach and conditioned motivation indicate that they depend upon different neurochemical systems, including the glutamatergic and adrenergic systems within limbic corticostriatal circuitry. We also discuss here the subsequent translation to the clinic of this preclinical work.
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Affiliation(s)
- Amy L Milton
- Department of Experimental Psychology, Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK.
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485
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Rehberg K, Bergado-Acosta JR, Koch JC, Stork O. Disruption of fear memory consolidation and reconsolidation by actin filament arrest in the basolateral amygdala. Neurobiol Learn Mem 2010; 94:117-26. [PMID: 20416387 DOI: 10.1016/j.nlm.2010.04.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 03/19/2010] [Accepted: 04/16/2010] [Indexed: 10/19/2022]
Abstract
The dynamic re-arrangement of actin filaments is an essential process in the plasticity of synaptic connections during memory formation. In this study, we determined in mice effects of actin filament arrest in the basolateral complex of the amygdala (BLA) at different time points after memory acquisition and re-activation, using the fungal cytotoxin phalloidin. Our data show a selective disruption of auditory cued but not contextual fear memory, when phalloidin was injected 6h after conditioning. In contrast, no effect was observed when phalloidin was applied after 24h, ruling out an interference with the retrieval or expression of conditioned fear. A comparable result was obtained after memory re-activation, hence suggesting similar actin-dependent mechanisms to be active during consolidation and reconsolidation of auditory fear memory. Biochemical analysis showed that phalloidin-mediated filament arrest leads to a transient increase of highly cross-linked actin filaments in the BLA, evident 2h after injection. Together, these observations indicate that dynamic re-arrangements of actin filaments in the BLA during a late phase of fear memory consolidation and reconsolidation are critical for fear memory storage.
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Affiliation(s)
- Kati Rehberg
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, 39120 Magdeburg, Germany
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486
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Abstract
Drug addiction is a chronic disorder associated with recurrent craving and relapse often precipitated by the presence of drug-associated stimuli. Pharmacological and behavioral treatments that disrupt drug-associated stimulus memories could be beneficial in the treatment of addictive disorders. Memory restabilization (or reconsolidation) following retrieval of drug-paired stimuli depends upon the amygdala. Here we assessed whether amygdalar PKA is required for the reconsolidation of an appetitive, cocaine-paired stimulus. Rats were trained to lever press for intravenous cocaine infusions paired with a light/tone conditioned stimulus. After 12 d of acquisition, rats either underwent lever extinction (8-12 d) followed by light/tone reactivation and subsequent cue-induced and cocaine-induced (15 mg/kg, i.p.) reinstatement testing or were subsequently tested to assess the ability of the light/tone stimulus to serve as a conditioned reinforcer in the acquisition of a new instrumental response (nose poking). Bilateral intra-amygdalar infusions of the PKA inhibitor Rp-cAMPS (18 microg per side) given immediately following light/tone stimulus reactivation decreased subsequent cue-induced reinstatement and responding with a conditioned reinforcer, while having no effect on cocaine-induced reinstatement. Intra-amygdalar infusions of Rp-cAMPS made 3 h following reactivation or immediately following no stimulus reactivation had no effect on subsequent cue-induced reinstatement. These data show that memory reconsolidation for a cocaine-paired stimulus is retrieval dependent and time limited and critically depends upon amygdalar PKA.
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487
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Bustos SG, Giachero M, Maldonado H, Molina VA. Previous stress attenuates the susceptibility to Midazolam's disruptive effect on fear memory reconsolidation: influence of pre-reactivation D-cycloserine administration. Neuropsychopharmacology 2010; 35:1097-108. [PMID: 20043007 PMCID: PMC3055408 DOI: 10.1038/npp.2009.215] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
It is well known that, under certain boundary conditions, the retrieval of a stable consolidated memory results into a labile one. During this unstable phase, memory can be vulnerable to interference by a number of pharmacological agents, including benzodiazepines. One of the goals of this study was to evaluate the vulnerability to midazolam (MDZ) after reactivation of recent and remote contextual fear memories in animals that experienced a stressful situation before learning. Animals were subjected to a restraint session and trained in a contextual fear paradigm the following day; consolidated memories were reactivated at different times after learning and different MDZ doses (1.5, 3.0 mg/kg) were administered to rats after reactivation. Our results show that MDZ did not affect memory reconsolidation in older-than-one-day memories of stressed animals, even after the administration of a higher MDZ dose and a longer reactivation session (5 min). In contrast, MDZ was effective in blocking reconsolidation at all memory ages in unstressed animals. In addition, the current research investigated whether activating NMDA sites before reactivation promotes the destabilization of resistant memories such as those of stressed animals. We tested the influence of pre-reactivation D-cycloserine (DCS), a partial NMDA agonist, on MDZ's effect on fear memory reconsolidation in stressed animals. Our findings indicate that DCS before reactivation promotes retrieval-induced lability in resistant memory traces, as MDZ-induced memory impairment in stressed rats became evident with pre-reactivation DCS but not after pre-reactivation sterile isotonic saline.
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Affiliation(s)
- Silvia Gabriela Bustos
- Departamento de Farmacología, IFEC-CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, Córdoba, Argentina
| | - Marcelo Giachero
- Departamento de Farmacología, IFEC-CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, Córdoba, Argentina
| | - Héctor Maldonado
- Laboratorio de Neurobiología de la Memoria, Departamento de Fisiología y Biología Molecular, IFIBYNE-CONICET, Pabellón II, Facultad de Ciencias Exactas y Naturales (C1428EHA), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Víctor Alejandro Molina
- Departamento de Farmacología, IFEC-CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, Córdoba, Argentina,Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, Córdoba 5000, Argentina, Tel: +51 0351 4334437, Fax: +0351 433 4420, E-mail:
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488
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The amygdala encodes specific sensory features of an aversive reinforcer. Nat Neurosci 2010; 13:536-7. [PMID: 20348916 PMCID: PMC2860669 DOI: 10.1038/nn.2520] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 02/24/2010] [Indexed: 11/08/2022]
Abstract
Studies of reconsolidation, in which retrieved memories are altered and restored, offer a novel approach for exploring the associative structure of fear memory. Here we show in rats that exposure to the unconditioned stimulus initiates an unconditioned stimulus–specific reconsolidation of learned fear that depends on the amygdala. Thus, specific features of the unconditioned stimulus appear to be encoded in the amygdala as part of fear memories stored there.
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489
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Ageta H, Ikegami S, Miura M, Masuda M, Migishima R, Hino T, Takashima N, Murayama A, Sugino H, Setou M, Kida S, Yokoyama M, Hasegawa Y, Tsuchida K, Aosaki T, Inokuchi K. Activin plays a key role in the maintenance of long-term memory and late-LTP. Learn Mem 2010; 17:176-85. [PMID: 20332189 DOI: 10.1101/lm.16659010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A recent study has revealed that fear memory may be vulnerable following retrieval, and is then reconsolidated in a protein synthesis-dependent manner. However, little is known about the molecular mechanisms of these processes. Activin betaA, a member of the TGF-beta superfamily, is increased in activated neuronal circuits and regulates dendritic spine morphology. To clarify the role of activin in the synaptic plasticity of the adult brain, we examined the effect of inhibiting or enhancing activin function on hippocampal long-term potentiation (LTP). We found that follistatin, a specific inhibitor of activin, blocked the maintenance of late LTP (L-LTP) in the hippocampus. In contrast, administration of activin facilitated the maintenance of early LTP (E-LTP). We generated forebrain-specific activin- or follistatin-transgenic mice in which transgene expression is under the control of the Tet-OFF system. Maintenance of hippocampal L-LTP was blocked in the follistatin-transgenic mice. In the contextual fear-conditioning test, we found that follistatin blocked the formation of long-term memory (LTM) without affecting short-term memory (STM). Furthermore, consolidated memory was selectively weakened by the expression of follistatin during retrieval, but not during the maintenance phase. On the other hand, the maintenance of memory was also influenced by activin overexpression during the retrieval phase. Thus, the level of activin in the brain during the retrieval phase plays a key role in the maintenance of long-term memory.
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Affiliation(s)
- Hiroshi Ageta
- Mitsubishi Kagaku Institute of Life Sciences, MITILS, Machida, Tokyo 194-8511, Japan
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490
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491
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Wang SH, Morris RGM. Hippocampal-neocortical interactions in memory formation, consolidation, and reconsolidation. Annu Rev Psychol 2010; 61:49-79, C1-4. [PMID: 19575620 DOI: 10.1146/annurev.psych.093008.100523] [Citation(s) in RCA: 305] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review, focusing on work using animals, updates a theoretical approach whose aim is to translate neuropsychological ideas about the psychological and anatomical organization of memory into the neurobiological domain. It is suggested that episodic-like memory consists of both automatic and controlled components, with the medial temporal mediation of memory encoding including neurobiological mechanisms that are primarily automatic or incidental. These ideas, in the cognitive and behavioral domain, are linked to neurophysiological ideas about cellular consolidation concerning synaptic potentiation, particularly the relationship between protein synthesis-dependent long-term changes and shorter-lasting post-translational mechanisms. Ideas from psychology about mental schemas are considered in relation to the phenomenon of systems consolidation and, specifically, about how prior knowledge can alter the rate at which consolidation occurs. Finally, the hippocampal-neocortical interactions theory is updated in relation to reconsolidation, a process that enables updating of stored memory traces in response to novelty.
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Affiliation(s)
- Szu-Han Wang
- Center for Cognitive and Neural Systems, Neuroscience, The University of Edinburgh, Edinburgh EH8 9JZ, Scotland.
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492
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Distress call-induced gene expression in the brain of the Indian short-nosed fruit bat, Cynopterus sphinx. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2010; 196:155-64. [DOI: 10.1007/s00359-009-0502-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 12/16/2009] [Accepted: 12/21/2009] [Indexed: 01/26/2023]
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493
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Jong YJI, Kumar V, O'Malley KL. Intracellular metabotropic glutamate receptor 5 (mGluR5) activates signaling cascades distinct from cell surface counterparts. J Biol Chem 2010; 284:35827-38. [PMID: 19840937 DOI: 10.1074/jbc.m109.046276] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G-protein-coupled receptors are thought to transmit extracellular signals to the cytoplasm from their position on the cell surface. Some receptors, including the metabotropic glutamate receptor 5 (mGluR5), are also highly expressed on intracellular membranes where they serve unknown functions. Here, we show that activation of cell surface versus intracellular mGluR5 results in unique Ca(2+) signatures leading to unique cellular responses. Specifically, activation of either cell surface or intracellular mGluR5 leads to JNK, Ca(2+)/calmodulin-dependent protein kinase (CaMK), and cyclic adenosine 3',5'-monophosphate-responsive element-binding protein phosphorylation, whereas activation of only intracellular mGluR5 leads to ERK1/2 and Elk-1 phosphorylation. Using pharmacological and genetic approaches, the present findings support a role for CaMK kinase in mediating mGluR5-dependent cyclic adenosine 3',5'-monophosphate-responsive element-binding protein phosphorylation, whereas CaMKII is upstream of intracellular mGluR5-mediated Elk-1 phosphorylation. Consistent with models showing Elk-1 regulating cascades of gene expression, the known Elk-1 targets c-fos and egr1 were up-regulated following intracellular mGluR5 activation, whereas a representative non-Elk-1 target, c-jun, was not. These findings emphasize that glutamate not only serves as a neurotransmitter for cell surface receptors but, when transported into the cell, can also activate intracellular receptors such as mGluR5. Glutamate activation of intracellular mGluR5 serves an important role in the regulation of nuclear Ca(2+), transcriptional activation, and gene expression necessary for physiological processes such as synaptic plasticity.
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Affiliation(s)
- Yuh-Jiin I Jong
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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494
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Zoladz PR, Woodson JC, Haynes VF, Diamond DM. Activation of a remote (1-year old) emotional memory interferes with the retrieval of a newly formed hippocampus-dependent memory in rats. Stress 2010; 13:36-52. [PMID: 19658031 DOI: 10.3109/10253890902853123] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The persistent intrusion of remote traumatic memories in people with post-traumatic stress disorder (PTSD) may contribute to the impairment of their ongoing hippocampal and prefrontal cortical functioning. In the current work, we have developed a rodent analogue of the intrusive memory phenomenon. We studied the influence of the activation of a remote traumatic memory in rats on their ability to retrieve a newly formed hippocampus-dependent memory. Adult male Sprague-Dawley rats were given inhibitory avoidance (IA) training, and then 24 h or 1, 6 or 12 months later, the same rats were trained to learn, and then remember across a 30-min delay period, the location of a hidden escape platform in the radial-arm water maze (RAWM). When IA-trained rats spent the 30-min delay period in the IA apparatus, they exhibited intact remote (1-year old) memory of the shock experience. More importantly, activation of the rats' memory of the shock experience profoundly impaired their ability to retrieve the newly formed spatial memory of the hidden platform location in the RAWM. Our finding that reactivation of a remote emotional memory exerted an intrusive effect on new spatial memory processing in rats provides a novel approach toward understanding how intrusive memories of traumatic experiences interfere with ongoing cognitive processing in people with PTSD.
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495
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Knight M, Mather M. Reconciling findings of emotion-induced memory enhancement and impairment of preceding items. Emotion 2009; 9:763-81. [PMID: 20001121 PMCID: PMC2917000 DOI: 10.1037/a0017281] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A large body of work has revealed that people remember emotionally arousing information better than neutral information. However, previous research has revealed contradictory effects of emotional events on memory for neutral events that precede or follow them: In some studies, emotionally arousing items have impaired memory for immediately preceding or following items, and in others arousing items enhanced memory for preceding items. By demonstrating both emotion-induced enhancement and impairment, Experiments 1 and 2 clarified the conditions under which these effects are likely to occur. The results suggest that emotion-induced enhancement is most likely to occur for neutral items that (a) precede (and so are poised to predict the onset of) emotionally arousing items, (b) have high attentional weights at encoding, and (c) are tested after a delay period of a week rather than within the same experimental session. In contrast, emotion-induced impairment is most likely to occur for neutral items near the onset of emotional arousal that are overshadowed by highly activated competing items during encoding.
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Affiliation(s)
- Marisa Knight
- Psychology Department, University of San Francisco, 2130 FultonStreet, San Francisco, CA 94117, USA.
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496
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Mueller D, Cahill SP. Noradrenergic modulation of extinction learning and exposure therapy. Behav Brain Res 2009; 208:1-11. [PMID: 19931568 DOI: 10.1016/j.bbr.2009.11.025] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2009] [Revised: 11/12/2009] [Accepted: 11/15/2009] [Indexed: 11/16/2022]
Abstract
Memory consolidation is enhanced by emotional arousal, an effect mediated by noradrenergic beta-receptor signaling. Norepinephrine strengthens consolidation of both appetitive and aversive learning, and is implicated in extinction of conditioned responses. In this review, we summarize work on the noradrenergic mechanisms of extinction learning and implications for extinction-based exposure therapy. The evidence suggests that norepinephrine release evoked by conditioned stimuli during extinction strengthens extinction memory via beta-receptor signaling. The modulatory effect of norepinephrine during extinction depends on predictable presentation of conditioned stimuli and optimal levels of norepinephrine release. Mechanistically, norepinephrine acts to increase cellular excitability and enhance synaptic plasticity within extinction-related neural circuitry. Currently, drugs that modulate norepinephrine are being used to treat symptoms of anxiety disorders, and are now being tested as pharmacotherapeutic prophalactics in the prevention of chronic posttraumatic stress reactions and as adjuncts to extinction-based exposure therapy. Studies of these new applications of noradrenergic drugs show a converging pattern of results with basic science suggesting ways in which basic laboratory findings can be translated into procedures to enhance clinical outcomes.
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Affiliation(s)
- Devin Mueller
- Department of Psychology, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201-0413, USA.
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497
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Bernardi RE, Ryabinin AE, Berger SP, Lattal KM. Post-retrieval disruption of a cocaine conditioned place preference by systemic and intrabasolateral amygdala beta2- and alpha1-adrenergic antagonists. Learn Mem 2009; 16:777-89. [PMID: 19940038 DOI: 10.1101/lm.1648509] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Previous work has demonstrated post-retrieval impairment in associative learning paradigms, including those mediated by drugs of abuse, using nonspecific beta-adrenergic receptor (beta-AR) antagonists. Remarkably little is known about the role of the specific beta-AR subtypes, or other adrenergic receptors, in these effects. The current study examined the effects of beta(1) and beta(2), as well as alpha(1)-adrenergic receptor antagonism following retrieval of a cocaine conditioned place preference (CPP). We found that rats administered the beta(2) antagonist ICI 118,551 (8 mg/kg intraperitoneal [IP]) or the alpha(1) antagonist prazosin (1 mg/kg IP) following a drug-free test for CPP showed attenuated preference during a subsequent test, while the beta(1) antagonist betaxolol (5 or 10 mg/kg IP) and a lower dose of prazosin (0.3 mg/kg IP) had no effect. Furthermore, post-test microinfusion of ICI 118,551 (6 nmol/side) or prazosin (0.5 nmol/side) into the basolateral amygdala (BLA) also impaired a subsequent preference. Systemic or intra-BLA ICI 118,551 or prazosin administered to rats in their home cages, in the absence of a preference test, had no effect on CPP 24 h later. ICI 118,551 also attenuated the FOS response in the BLA induced by the CPP test. These results are the first to demonstrate a role for alpha(1)- and beta(2)-specific adrenergic mechanisms in post-retrieval memory processes. These systemic and site-specific injections, as well as the FOS immunohistochemical analyses, implicate the importance of specific noradrenergic signaling mechanisms within the BLA in post-retrieval plasticity.
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Affiliation(s)
- Rick E Bernardi
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oregon 97239, USA.
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498
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The Hippocampal System as the Cortical Resource Manager: A Model Connecting Psychology, Anatomy and Physiology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 657:315-64. [DOI: 10.1007/978-0-387-79100-5_18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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499
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Languille S, Davis S, Richer P, Alcacer C, Laroche S, Hars B. Extracellular signal-regulated kinase activation is required for consolidation and reconsolidation of memory at an early stage of ontogenesis. Eur J Neurosci 2009; 30:1923-30. [DOI: 10.1111/j.1460-9568.2009.06971.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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500
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Pharmacological discrimination of extinction and reconsolidation of contextual fear memory by a potentiator of AMPA receptors. Neuropsychopharmacology 2009; 34:2574-84. [PMID: 19675539 DOI: 10.1038/npp.2009.86] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Conditioned fear memory, once formed through fear conditioning, is modulated by reexposure of individuals to a conditioned stimulus. The reexposure reactivates the fear memory, which induces reconsolidation of the memory first, and then extinction of the fear response. Both attenuating the former and facilitating the latter are effective in reducing the fear response, and these findings are potentially translatable to the enhancement of exposure therapy for complex anxiety disorders. Currently, there is no drug that is established to modulate either reconsolidation or extinction selectively, which are thought to be independent processes. Here, we report that an extinction-facilitating AMPA potentiator, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), does not act on the reconsolidation of fear memory formed by contextual fear conditioning in mice. The freezing rates observed in contextually conditioned mice following short reexposure (3 min) to the context were not influenced by intraperitoneal or intra-amygdala administration of PEPA. The same short reexposure to the context enhanced freezing responses in mice that were similarly administered D-cycloserine (DCS), a drug that facilitates both extinction and reconsolidation, and this enhancement of freezing responses in mice intraperitoneally administered DCS was abolished by propranolol, a drug that suppresses reconsolidation. At the same doses used in the short reexposure experiments, PEPA and DCS facilitated extinction of the fear response induced by long reexposure to the context and suppressed reinstatement of the conditioned fear memory. PEPA and DCS did not affect reextinction. These results suggest that PEPA acts on extinction of contextual fear memory without having detectable influences on its reconsolidation.
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