601
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Krasne FB, Fanselow MS, Zelikowsky M. Design of a neurally plausible model of fear learning. Front Behav Neurosci 2011; 5:41. [PMID: 21845175 PMCID: PMC3145244 DOI: 10.3389/fnbeh.2011.00041] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 07/07/2011] [Indexed: 01/07/2023] Open
Abstract
A neurally oriented conceptual and computational model of fear conditioning manifested by freezing behavior (FRAT), which accounts for many aspects of delay and context conditioning, has been constructed. Conditioning and extinction are the result of neuromodulation-controlled LTP at synapses of thalamic, cortical, and hippocampal afferents on principal cells and inhibitory interneurons of lateral and basal amygdala. The phenomena accounted for by the model (and simulated by the computational version) include conditioning, secondary reinforcement, blocking, the immediate shock deficit, extinction, renewal, and a range of empirically valid effects of pre- and post-training ablation or inactivation of hippocampus or amygdala nuclei.
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Affiliation(s)
- Franklin B Krasne
- Department of Psychology, University of California Los Angeles Los Angeles, CA, USA
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602
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Lamprecht R. The roles of the actin cytoskeleton in fear memory formation. Front Behav Neurosci 2011; 5:39. [PMID: 21808614 PMCID: PMC3139223 DOI: 10.3389/fnbeh.2011.00039] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Accepted: 07/02/2011] [Indexed: 01/08/2023] Open
Abstract
The formation and storage of fear memory is needed to adapt behavior and avoid danger during subsequent fearful events. However, fear memory may also play a significant role in stress and anxiety disorders. When fear becomes disproportionate to that necessary to cope with a given stimulus, or begins to occur in inappropriate situations, a fear or anxiety disorder exists. Thus, the study of cellular and molecular mechanisms underpinning fear memory may shed light on the formation of memory and on anxiety and stress related disorders. Evidence indicates that fear learning leads to changes in neuronal synaptic transmission and morphology in brain areas underlying fear memory formation including the amygdala and hippocampus. The actin cytoskeleton has been shown to participate in these key neuronal processes. Recent findings show that the actin cytoskeleton is needed for fear memory formation and extinction. Moreover, the actin cytoskeleton is involved in synaptic plasticity and in neuronal morphogenesis in brain areas that mediate fear memory. The actin cytoskeleton may therefore mediate between synaptic transmission during fear learning and long-term cellular alterations mandatory for fear memory formation.
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Affiliation(s)
- Raphael Lamprecht
- Faculty of Natural Sciences, Department of Neurobiology and Ethology, University of Haifa Haifa, Israel
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603
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Pagani JH, Lee HJ, Young WS. Postweaning, forebrain-specific perturbation of the oxytocin system impairs fear conditioning. GENES BRAIN AND BEHAVIOR 2011; 10:710-9. [PMID: 21668734 DOI: 10.1111/j.1601-183x.2011.00709.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Oxytocin (Oxt) and vasopressin (Avp) are important for a wide variety of behaviors and the use of transgenic mice lacking the peptides or their receptors, particularly when their loss is spatially and temporally manipulated, offers an opportunity to closely examine their role in a particular behavior. We used a cued fear conditioning paradigm to examine associative learning in three lines of transgenic mice: mice that constitutively lack vasopressin 1a (Avpr1a(-/-)) or Oxt receptors (Oxtr(-/-)) and mice that have Oxt receptor loss restricted to the forebrain that begins postweaning (Oxtr(FB/FB)). Oxtr(-/-) and Avpr1a(-/-) mice have normal conditioned freezing. Oxtr(FB/FB) mice have a reduction in freezing behavior during acquisition, as well as during context and cue retention. In addition to reduction of Oxtr in the central nucleus of the amygdala, in vitro receptor autoradiography showed that the Oxtr(FB/FB) mice have significantly reduced levels of Avpr1a only in that structure. Our results show that postweaning alteration of the distribution of Oxtr receptors is critically important for fear behavior, an effect mirrored in the neural structures that mediate it. While constitutive knockouts of Oxtr and Avpr1a are useful for identifying the neural underpinnings of some behaviors, compensatory mechanisms within some circuits may obscure other behavioral roles.
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Affiliation(s)
- J H Pagani
- Section on Neural Gene Expression, NIMH, NIH, DHHS, Bethesda, MD 20892-4483, USA
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604
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Viviani D, Charlet A, van den Burg E, Robinet C, Hurni N, Abatis M, Magara F, Stoop R. Oxytocin Selectively Gates Fear Responses Through Distinct Outputs from the Central Amygdala. Science 2011; 333:104-7. [DOI: 10.1126/science.1201043] [Citation(s) in RCA: 283] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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605
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Abstract
Large-scale projects are providing rapid global access to a wealth of mouse genetic resources to help discover disease genes and to manipulate their function.
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Affiliation(s)
| | | | - David J Adams
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
| | - Darren W Logan
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
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606
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Abstract
Learning to contend with threats in the environment is essential to survival, but dysregulation of memories for traumatic events can lead to disabling psychopathology. Recent years have witnessed an impressive growth in our understanding of the neural systems and synaptic mechanisms underlying emotional memory formation. As a consequence, interest has emerged in developing strategies for suppressing, if not eliminating, fear memories. Here, I review recent work employing sophisticated behavioral, pharmacological, and molecular tools to target fear memories, placing these memories firmly behind the crosshairs of neurobiologically informed interventions.
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Affiliation(s)
- Stephen Maren
- Department of Psychology and Neuroscience Program, University of Michigan, Ann Arbor, MI 48109-1043, USA.
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607
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Amir A, Amano T, Pare D. Physiological identification and infralimbic responsiveness of rat intercalated amygdala neurons. J Neurophysiol 2011; 105:3054-66. [PMID: 21471396 PMCID: PMC3118749 DOI: 10.1152/jn.00136.2011] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 04/03/2011] [Indexed: 11/22/2022] Open
Abstract
Intercalated (ITC) amygdala neurons are thought to play a critical role in the extinction of conditioned fear. However, several factors hinder progress in studying ITC contributions to extinction. First, although extinction is usually studied in rats and mice, most ITC investigations were performed in guinea pigs or cats. Thus it is unclear whether their connectivity is similar across species. Second, we lack criteria to identify ITC cells on the basis of their discharge pattern. As a result, key predictions of ITC extinction models remain untested. Among these, ITC cells were predicted to be strongly excited by infralimbic inputs, explaining why infralimbic inhibition interferes with extinction. To study the connectivity of ITC cells, we labeled them with neurobiotin during patch recordings in slices of the rat amygdala. This revealed that medially located ITC cells project topographically to the central nucleus and to other ITC clusters located more ventrally. To study the infralimbic responsiveness of ITC cells, we performed juxtacellular recording and labeling of amygdala cells with neurobiotin in anesthetized rats. All ITC cells were orthodromically responsive to infralimbic stimuli, and their responses usually consisted of high-frequency (~350 Hz) trains of four to six spikes, a response pattern never seen in neighboring amygdala nuclei. Overall, our results suggest that the connectivity of ITC cells is conserved across species and that ITC cells are strongly responsive to infralimbic stimuli, as predicted by extinction models. The unique response pattern of ITC cells to infralimbic stimuli can now be used to identify them in fear conditioning experiments.
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Affiliation(s)
- Alon Amir
- Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, NJ 07102, USA
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608
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Ciocchi S, Lüthi A, Herry C. [Novel amygdala neuronal circuits controlling fear behavior]. Med Sci (Paris) 2011; 27:455-7. [PMID: 21609659 DOI: 10.1051/medsci/2011275003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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609
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McNally GP, Johansen JP, Blair HT. Placing prediction into the fear circuit. Trends Neurosci 2011; 34:283-92. [PMID: 21549434 DOI: 10.1016/j.tins.2011.03.005] [Citation(s) in RCA: 193] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 03/28/2011] [Accepted: 03/29/2011] [Indexed: 10/18/2022]
Abstract
Pavlovian fear conditioning depends on synaptic plasticity at amygdala neurons. Here, we review recent electrophysiological, molecular and behavioral evidence suggesting the existence of a distributed neural circuitry regulating amygdala synaptic plasticity during fear learning. This circuitry, which involves projections from the midbrain periaqueductal gray region, can be linked to prediction error and expectation modulation of fear learning, as described by associative and computational learning models. It controls whether, and how much, fear learning occurs by signaling aversive events when they are unexpected. Functional neuroimaging and clinical studies indicate that this prediction circuit is recruited in humans during fear learning and contributes to exposure-based treatments for clinical anxiety. This aversive prediction error circuit might represent a conserved mechanism for regulating fear learning in mammals.
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Affiliation(s)
- Gavan P McNally
- School of Psychology, The University of New South Wales, Sydney, NSW, Australia.
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610
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Vogt KE. Dousing the flames of fear. J Physiol 2011; 589:1865. [PMID: 21498379 DOI: 10.1113/jphysiol.2011.206920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Kaspar E Vogt
- Pharmacology/Neurobiology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
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611
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Li G, Amano T, Pare D, Nair SS. Impact of infralimbic inputs on intercalated amygdala neurons: a biophysical modeling study. Learn Mem 2011; 18:226-40. [PMID: 21436395 DOI: 10.1101/lm.1938011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Intercalated (ITC) amygdala neurons regulate fear expression by controlling impulse traffic between the input (basolateral amygdala; BLA) and output (central nucleus; Ce) stations of the amygdala for conditioned fear responses. Previously, stimulation of the infralimbic (IL) cortex was found to reduce fear expression and the responsiveness of Ce neurons to BLA inputs. These effects were hypothesized to result from the activation of ITC cells projecting to Ce. However, ITC cells inhibit each other, leading to the question of how IL inputs could overcome the inter-ITC inhibition to regulate the responses of Ce neurons to aversive conditioned stimuli (CSs). To investigate this, we first developed a compartmental model of a single ITC cell that could reproduce their bistable electroresponsive properties, as observed experimentally. Next, we generated an ITC network that implemented the experimentally observed short-term synaptic plasticity of inhibitory inter-ITC connections. Model experiments showed that strongly adaptive CS-related BLA inputs elicited persistent responses in ITC cells despite the presence of inhibitory interconnections. The sustained CS-evoked activity of ITC cells resulted from an unusual slowly deinactivating K(+) current. Finally, over a wide range of stimulation strengths, brief IL activation caused a marked increase in the firing rate of ITC neurons, leading to a persistent decrease in Ce output, despite inter-ITC inhibition. Simulations revealed that this effect depended on the bistable properties and synaptic heterogeneity of ITC neurons. These results support the notion that IL inputs are in a strategic position to control extinction of conditioned fear via the activation of ITC neurons.
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Affiliation(s)
- Guoshi Li
- Department of Psychology, Cornell University, Ithaca, New York 14850, USA
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612
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Abstract
A significant challenge for neuroscientists is to determine how both electrical and chemical signals affect the activity of cells and circuits and how the nervous system subsequently translates that activity into behavior. Remote, bidirectional manipulation of those signals with high spatiotemporal precision is an ideal approach to addressing that challenge. Neuroscientists have recently developed a diverse set of tools that permit such experimental manipulation with varying degrees of spatial, temporal, and directional control. These tools use light, peptides, and small molecules to primarily activate ion channels and G protein-coupled receptors (GPCRs) that in turn activate or inhibit neuronal firing. By monitoring the electrophysiological, biochemical, and behavioral effects of such activation/inhibition, researchers can better understand the links between brain activity and behavior. Here, we review the tools that are available for this type of experimentation. We describe the development of the tools and highlight exciting in vivo data. We focus primarily on designer GPCRs (receptors activated solely by synthetic ligands, designer receptors exclusively activated by designer drugs) and microbial opsins (e.g., channelrhodopsin-2, halorhodopsin, Volvox carteri channelrhodopsin) but also describe other novel techniques that use orthogonal receptors, caged ligands, allosteric modulators, and other approaches. These tools differ in the direction of their effect (activation/inhibition, hyperpolarization/depolarization), their onset and offset kinetics (milliseconds/minutes/hours), the degree of spatial resolution they afford, and their invasiveness. Although none of these tools is perfect, each has advantages and disadvantages, which we describe, and they are all still works in progress. We conclude with suggestions for improving upon the existing tools.
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Affiliation(s)
- Sarah C Rogan
- University of North Carolina School of Medicine, Department of Pharmacology, 120 Mason Farm Rd, Chapel Hill, NC 27514, USA
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613
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Tye KM, Prakash R, Kim SY, Fenno LE, Grosenick L, Zarabi H, Thompson KR, Gradinaru V, Ramakrishnan C, Deisseroth K. Amygdala circuitry mediating reversible and bidirectional control of anxiety. Nature 2011; 471:358-62. [PMID: 21389985 DOI: 10.1038/nature09820] [Citation(s) in RCA: 882] [Impact Index Per Article: 67.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 01/14/2011] [Indexed: 11/09/2022]
Abstract
Anxiety--a sustained state of heightened apprehension in the absence of immediate threat--becomes severely debilitating in disease states. Anxiety disorders represent the most common of psychiatric diseases (28% lifetime prevalence) and contribute to the aetiology of major depression and substance abuse. Although it has been proposed that the amygdala, a brain region important for emotional processing, has a role in anxiety, the neural mechanisms that control anxiety remain unclear. Here we explore the neural circuits underlying anxiety-related behaviours by using optogenetics with two-photon microscopy, anxiety assays in freely moving mice, and electrophysiology. With the capability of optogenetics to control not only cell types but also specific connections between cells, we observed that temporally precise optogenetic stimulation of basolateral amygdala (BLA) terminals in the central nucleus of the amygdala (CeA)--achieved by viral transduction of the BLA with a codon-optimized channelrhodopsin followed by restricted illumination in the downstream CeA--exerted an acute, reversible anxiolytic effect. Conversely, selective optogenetic inhibition of the same projection with a third-generation halorhodopsin (eNpHR3.0) increased anxiety-related behaviours. Importantly, these effects were not observed with direct optogenetic control of BLA somata, possibly owing to recruitment of antagonistic downstream structures. Together, these results implicate specific BLA-CeA projections as critical circuit elements for acute anxiety control in the mammalian brain, and demonstrate the importance of optogenetically targeting defined projections, beyond simply targeting cell types, in the study of circuit function relevant to neuropsychiatric disease.
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Affiliation(s)
- Kay M Tye
- Department of Bioengineering, Stanford University, Stanford, California 94305, USA
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614
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Lüscher C, Malenka RC. Drug-evoked synaptic plasticity in addiction: from molecular changes to circuit remodeling. Neuron 2011; 69:650-63. [PMID: 21338877 PMCID: PMC4046255 DOI: 10.1016/j.neuron.2011.01.017] [Citation(s) in RCA: 774] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2011] [Indexed: 12/20/2022]
Abstract
Addictive drugs have in common that they target the mesocorticolimbic dopamine (DA) system. This system originates in the ventral tegmental area (VTA) and projects mainly to the nucleus accumbens (NAc) and prefrontal cortex (PFC). Here, we review the effects that such drugs leave on glutamatergic and GABAergic synaptic transmission in these three brain areas. We refer to these changes as drug-evoked synaptic plasticity, which outlasts the presence of the drug in the brain and contributes to the reorganization of neural circuits. While in most cases these early changes are not sufficient to induce the disease, with repetitive drug exposure, they may add up and contribute to addictive behavior.
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Affiliation(s)
- Christian Lüscher
- Department of Basic Neuroscience, University of Geneva, 1211 Geneva, Switzerland.
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615
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Optogenetic investigation of neural circuits in vivo. Trends Mol Med 2011; 17:197-206. [PMID: 21353638 DOI: 10.1016/j.molmed.2010.12.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/13/2010] [Accepted: 12/14/2010] [Indexed: 01/23/2023]
Abstract
The recent development of light-activated optogenetic probes allows for the identification and manipulation of specific neural populations and their connections in awake animals with unprecedented spatial and temporal precision. This review describes the use of optogenetic tools to investigate neurons and neural circuits in vivo. We describe the current panel of optogenetic probes, methods of targeting these probes to specific cell types in the nervous system, and strategies of photostimulating cells in awake, behaving animals. Finally, we survey the application of optogenetic tools to studying functional neuroanatomy, behavior and the etiology and treatment of various neurological disorders.
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616
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Fear: a frightful circuit. Nat Rev Neurosci 2011; 12:2. [PMID: 21218566 DOI: 10.1038/nrn2975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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617
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Encoding of conditioned fear in central amygdala inhibitory circuits. Nature 2010; 468:277-82. [DOI: 10.1038/nature09559] [Citation(s) in RCA: 682] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Accepted: 10/07/2010] [Indexed: 12/18/2022]
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