51
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Shumake J, Jones C, Auchter A, Monfils MH. Data-driven criteria to assess fear remission and phenotypic variability of extinction in rats. Philos Trans R Soc Lond B Biol Sci 2019; 373:rstb.2017.0035. [PMID: 29352033 DOI: 10.1098/rstb.2017.0035] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/09/2017] [Indexed: 12/30/2022] Open
Abstract
Fear conditioning is widely employed to examine the mechanisms that underlie dysregulations of the fear system. Various manipulations are often used following fear acquisition to attenuate fear memories. In rodent studies, freezing is often the main output measure to quantify 'fear'. Here, we developed data-driven criteria for defining a standard benchmark that indicates remission from conditioned fear and for identifying subgroups with differential treatment responses. These analyses will enable a better understanding of individual differences in treatment responding.This article is part of a discussion meeting issue 'Of mice and mental health: facilitating dialogue between basic and clinical neuroscientists'.
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Affiliation(s)
- Jason Shumake
- Institute for Mental Health Research, The University of Texas at Austin, Austin, TX, USA.,Department of Psychology, The University of Texas at Austin, Austin, TX, USA
| | - Carolyn Jones
- Department of Psychology, The University of Texas at Austin, Austin, TX, USA
| | - Allison Auchter
- Department of Psychology, The University of Texas at Austin, Austin, TX, USA
| | - Marie-Hélène Monfils
- Institute for Mental Health Research, The University of Texas at Austin, Austin, TX, USA .,Department of Psychology, The University of Texas at Austin, Austin, TX, USA
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52
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Martínez-Rivera FJ, Bravo-Rivera C, Velázquez-Díaz CD, Montesinos-Cartagena M, Quirk GJ. Prefrontal circuits signaling active avoidance retrieval and extinction. Psychopharmacology (Berl) 2019; 236:399-406. [PMID: 30259076 PMCID: PMC6461357 DOI: 10.1007/s00213-018-5012-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 08/28/2018] [Indexed: 12/17/2022]
Abstract
OBJECTIVE Neurons in PL and IL project densely to two areas implicated in active avoidance: the basolateral amygdala (BLA) and the ventral striatum (VS). We therefore combined c-Fos immunohistochemistry with retrograde tracers to characterize signaling in platform-mediated active avoidance. METHODS Male rats were infused with retrograde tracers (CTB, FB) into basolateral amygdala and ventral striatum and conditioned to avoid tone-signaled footshocks by stepping onto a nearby platform. In a subsequent test session, rats received either 2 unreinforced tones (avoidance retrieval) or 15 unreinforced tones (avoidance extinction) followed by analysis of c-Fos combined with fluorescent imaging of retrograde tracers. RESULTS Retrieval of avoidance did not activate IL neurons, but did activate PL neurons projecting to BLA, and to a lesser extent VS. Extinction of avoidance activated IL neurons projecting to both BLA and VS, as well as PL neurons projecting to VS. CONCLUSIONS Our observation that avoidance retrieval is signaled by PL projections to BLA suggests that PL may modulate VS indirectly via BLA, and agrees with other findings implicating BLA in active avoidance. Less expected was the signaling of extinction via PL inputs to VS, which may converge with IL inputs to VS to inhibit expression of avoidance.
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Affiliation(s)
- Freddyson J Martínez-Rivera
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, P.O. Box 365067, San Juan, 00936-5067, Puerto Rico.
| | - Christian Bravo-Rivera
- Neuroscience Division, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Coraly D Velázquez-Díaz
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, P.O. Box 365067, San Juan, 00936-5067, Puerto Rico
| | - Marlian Montesinos-Cartagena
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, P.O. Box 365067, San Juan, 00936-5067, Puerto Rico
| | - Gregory J Quirk
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, P.O. Box 365067, San Juan, 00936-5067, Puerto Rico
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53
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Murray SB, Strober M, Craske MG, Griffiths S, Levinson CA, Strigo IA. Fear as a translational mechanism in the psychopathology of anorexia nervosa. Neurosci Biobehav Rev 2018; 95:383-395. [DOI: 10.1016/j.neubiorev.2018.10.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 10/11/2018] [Accepted: 10/22/2018] [Indexed: 12/30/2022]
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54
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Rosas-Vidal LE, Lozada-Miranda V, Cantres-Rosario Y, Vega-Medina A, Melendez L, Quirk GJ. Alteration of BDNF in the medial prefrontal cortex and the ventral hippocampus impairs extinction of avoidance. Neuropsychopharmacology 2018; 43:2636-2644. [PMID: 30127343 PMCID: PMC6224579 DOI: 10.1038/s41386-018-0176-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 07/11/2018] [Accepted: 07/24/2018] [Indexed: 01/09/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) is critical for establishing activity-related neural plasticity. There is increasing interest in the mechanisms of active avoidance and its extinction, but little is known about the role of BDNF in these processes. Using the platform-mediated avoidance task combined with local infusions of an antibody against BDNF, we show that blocking BDNF in either prelimbic (PL) or infralimbic (IL) medial prefrontal cortex during extinction training impairs subsequent recall of extinction of avoidance, differing from extinction of conditioned freezing. By combining retrograde tracers with BDNF immunohistochemistry, we show that extinction of avoidance increases BDNF expression in ventral hippocampal (vHPC) neurons, but not amygdala neurons, projecting to PL and IL. Using the CRISPR/Cas9 system, we further show that reducing BDNF production in vHPC neurons impairs recall of avoidance extinction. Thus, the vHPC may mediate behavioral flexibility in avoidance by driving extinction-related plasticity via BDNFergic projections to both PL and IL. These findings add to the growing body of knowledge implicating the hippocampal-prefrontal pathway in anxiety-related disorders and extinction-based therapies.
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Affiliation(s)
- Luis E Rosas-Vidal
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico, USA
- Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Valeria Lozada-Miranda
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico, USA
| | - Yisel Cantres-Rosario
- Department of Microbiology and Medical Zoology, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico, USA
| | - Alexis Vega-Medina
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico, USA
| | - Loyda Melendez
- Department of Microbiology and Medical Zoology, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico, USA
| | - Gregory J Quirk
- Departments of Psychiatry and Anatomy & Neurobiology, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico, USA.
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55
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Abstract
Active avoidance is the prototypical paradigm for studying aversively-motivated instrumental behavior. However, avoidance research stalled amid heated theoretical debates and the hypothesis that active avoidance is essentially Pavlovian flight. Here I reconsider key "avoidance problems" and review neurobehavioral data collected with modern tools. Although the picture remains incomplete, these studies strongly suggest that avoidance has an instrumental component and is mediated by brain circuits that resemble appetitive instrumental actions more than Pavlovian fear reactions. Rapid progress may be possible if investigators consider important factors like safety signals, response-competition, goal-directed vs. habitual control and threat imminence in avoidance study design. Since avoidance responses likely contribute to active coping, this research has important implications for understanding human resilience and disorders of control.
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Affiliation(s)
- Christopher K Cain
- NYU School of Medicine, Dept. of Child & Adolescent Psychiatry, 1 Park Avenue, 8 Floor, New York, NY 10016.,Nathan S. Kline Institute for Psychiatric Research, Emotional Brain Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962
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56
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Dynamics of defensive response mobilization during repeated terminations of exposure to increasing interoceptive threat. Int J Psychophysiol 2018; 131:44-56. [DOI: 10.1016/j.ijpsycho.2017.09.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 09/08/2017] [Accepted: 09/20/2017] [Indexed: 11/22/2022]
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57
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Avesar D, Stephens EK, Gulledge AT. Serotonergic Regulation of Corticoamygdalar Neurons in the Mouse Prelimbic Cortex. Front Neural Circuits 2018; 12:63. [PMID: 30131678 PMCID: PMC6090182 DOI: 10.3389/fncir.2018.00063] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 07/16/2018] [Indexed: 12/20/2022] Open
Abstract
Neuromodulatory transmitters, such as serotonin (5-HT), selectively regulate the excitability of subpopulations of cortical projection neurons to gate cortical output to specific target regions. For instance, in the mouse prelimbic cortex, 5-HT selectively excites commissurally projecting (COM) intratelencephalic neurons via activation of 5-HT2A (2A) receptors, while simultaneously inhibiting, via 5-HT1A (1A) receptors, corticofugally projecting pyramidal neurons targeting the pons. Here we characterize the physiology, morphology, and serotonergic regulation of corticoamygdalar (CAm) projection neurons in the mouse prelimbic cortex. Layer 5 CAm neurons shared a number of physiological and morphological characteristics with COM neurons, including higher input resistances, smaller HCN-channel mediated responses, and sparser dendritic arbors than corticopontine neurons. Across cortical lamina, CAm neurons also resembled COM neurons in their serotonergic modulation; focally applied 5-HT (100 μM; 1 s) generated 2A-receptor-mediated excitation, or 1A- and 2A-dependent biphasic responses, in ipsilaterally and contralaterally projecting CAm neurons. Serotonergic excitation depended on extrinsic excitatory drive, as 5-HT failed to depolarize CAm neurons from rest, but could enhance the number of action potentials generated by simulated barrages of synaptic input. Finally, using dual tracer injections, we identified double-labeled CAm/COM neurons that displayed primarily excitatory or biphasic responses to 5-HT. Overall, our findings reveal that prelimbic CAm neurons in layer 5 overlap, at least partially, with COM neurons, and that neurons projecting to either, or both targets, exhibit 2A-dependent serotonergic excitation. These results suggest that 5-HT, acting at 2A receptors, may promote cortical output to the amygdala.
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Affiliation(s)
| | | | - Allan T. Gulledge
- Department of Molecular and Systems Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH, United States
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58
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Piantadosi PT, Yeates DC, Floresco SB. Cooperative and dissociable involvement of the nucleus accumbens core and shell in the promotion and inhibition of actions during active and inhibitory avoidance. Neuropharmacology 2018; 138:57-71. [DOI: 10.1016/j.neuropharm.2018.05.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 05/07/2018] [Accepted: 05/21/2018] [Indexed: 11/28/2022]
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59
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Diehl MM, Lempert KM, Parr AC, Ballard I, Steele VR, Smith DV. Toward an integrative perspective on the neural mechanisms underlying persistent maladaptive behaviors. Eur J Neurosci 2018; 48:1870-1883. [PMID: 30044022 PMCID: PMC6113118 DOI: 10.1111/ejn.14083] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Revised: 06/13/2018] [Accepted: 06/26/2018] [Indexed: 01/29/2023]
Affiliation(s)
- Maria M. Diehl
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, PR 00936
| | - Karolina M. Lempert
- Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104
| | - Ashley C. Parr
- Centre for Neuroscience Studies, Queen’s University, Kingston, Ontario
| | - Ian Ballard
- Neurosciences Graduate Training Program, Stanford University, Stanford, CA 94305
| | - Vaughn R. Steele
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | - David V. Smith
- Department of Psychology, Temple University, Philadelphia, PA 19122
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60
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Diehl MM, Bravo-Rivera C, Rodriguez-Romaguera J, Pagan-Rivera PA, Burgos-Robles A, Roman-Ortiz C, Quirk GJ. Active avoidance requires inhibitory signaling in the rodent prelimbic prefrontal cortex. eLife 2018; 7:34657. [PMID: 29851381 PMCID: PMC5980229 DOI: 10.7554/elife.34657] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 05/06/2018] [Indexed: 12/27/2022] Open
Abstract
Much is known about the neural circuits of conditioned fear and its relevance to understanding anxiety disorders, but less is known about other anxiety-related behaviors such as active avoidance. Using a tone-signaled, platform-mediated avoidance task, we observed that pharmacological inactivation of the prelimbic prefrontal cortex (PL) delayed avoidance. Surprisingly, optogenetic silencing of PL glutamatergic neurons did not delay avoidance. Consistent with this, inhibitory but not excitatory responses of rostral PL neurons were associated with avoidance training. To test the importance of these inhibitory responses, we optogenetically stimulated PL neurons to counteract the tone-elicited reduction in firing rate. Photoactivation of rostral (but not caudal) PL neurons at 4 Hz impaired avoidance. These findings suggest that inhibitory responses of rostral PL neurons signal the avoidability of a potential threat and underscore the importance of designing behavioral optogenetic studies based on neuronal firing responses.
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Affiliation(s)
- Maria M Diehl
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, Puerto Rico.,Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, Puerto Rico
| | - Christian Bravo-Rivera
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, Puerto Rico.,Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, Puerto Rico
| | - Jose Rodriguez-Romaguera
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, Puerto Rico.,Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, Puerto Rico
| | - Pablo A Pagan-Rivera
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, Puerto Rico.,Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, Puerto Rico
| | - Anthony Burgos-Robles
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Ciorana Roman-Ortiz
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, Puerto Rico.,Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, Puerto Rico
| | - Gregory J Quirk
- Department of Psychiatry, University of Puerto Rico School of Medicine, San Juan, Puerto Rico.,Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, Puerto Rico
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61
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Gallo FT, Katche C, Morici JF, Medina JH, Weisstaub NV. Immediate Early Genes, Memory and Psychiatric Disorders: Focus on c-Fos, Egr1 and Arc. Front Behav Neurosci 2018; 12:79. [PMID: 29755331 PMCID: PMC5932360 DOI: 10.3389/fnbeh.2018.00079] [Citation(s) in RCA: 214] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 04/10/2018] [Indexed: 01/08/2023] Open
Abstract
Many psychiatric disorders, despite their specific characteristics, share deficits in the cognitive domain including executive functions, emotional control and memory. However, memory deficits have been in many cases undervalued compared with other characteristics. The expression of Immediate Early Genes (IEGs) such as, c-fos, Egr1 and arc are selectively and promptly upregulated in learning and memory among neuronal subpopulations in regions associated with these processes. Changes in expression in these genes have been observed in recognition, working and fear related memories across the brain. Despite the enormous amount of data supporting changes in their expression during learning and memory and the importance of those cognitive processes in psychiatric conditions, there are very few studies analyzing the direct implication of the IEGs in mental illnesses. In this review, we discuss the role of some of the most relevant IEGs in relation with memory processes affected in psychiatric conditions.
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Affiliation(s)
- Francisco T Gallo
- Instituto de Fisiología y Biofísica Bernardo Houssay, Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina
| | - Cynthia Katche
- Instituto de Biología Celular y Neurociencias (IBCN) Dr. Eduardo de Robertis, Facultad de Medicina, CONICET, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina
| | - Juan F Morici
- Instituto de Fisiología y Biofísica Bernardo Houssay, Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina
| | - Jorge H Medina
- Instituto de Biología Celular y Neurociencias (IBCN) Dr. Eduardo de Robertis, Facultad de Medicina, CONICET, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina.,Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos (UBA), Buenos Aires, Argentina
| | - Noelia V Weisstaub
- Instituto de Fisiología y Biofísica Bernardo Houssay, Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina
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62
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Neural Activity in Ventral Medial Prefrontal Cortex Is Modulated More Before Approach Than Avoidance During Reinforced and Extinction Trial Blocks. J Neurosci 2018; 38:4584-4597. [PMID: 29661965 DOI: 10.1523/jneurosci.2579-17.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 04/04/2018] [Accepted: 04/11/2018] [Indexed: 11/21/2022] Open
Abstract
Ventromedial prefrontal cortex (vmPFC) is thought to provide regulatory control over Pavlovian fear responses and has recently been implicated in appetitive approach behavior, but much less is known about its role in contexts in which appetitive and aversive outcomes can be obtained and avoided, respectively. To address this issue, we recorded from single neurons in vmPFC while male rats performed our combined approach and avoidance task under reinforced and non-reinforced (extinction) conditions. Surprisingly, we found that cues predicting reward modulated cell firing in vmPFC more often and more robustly than cues preceding avoidable shock; in addition, firing of vmPFC neurons was both response (press or no-press) and outcome (reinforced or extinction) selective. These results suggest a complex role for vmPFC in regulating behavior and support its role in appetitive contexts during both reinforced and non-reinforced conditions.SIGNIFICANCE STATEMENT Selecting context-appropriate behaviors to gain reward or avoid punishment is critical for survival. Although the role of ventromedial prefrontal cortex (vmPFC) in mediating fear responses is well established, vmPFC has also been implicated in the regulation of reward-guided approach and extinction. Many studies have used indirect methods and simple behavioral procedures to study vmPFC, which leaves the literature incomplete. We recorded vmFPC neural activity during a complex cue-driven combined approach and avoidance task and during extinction. Surprisingly, we found very little vmPFC modulation to cues predicting avoidable shock, whereas cues predicting reward approach robustly modulated vmPFC firing in a response- and outcome-selective manner. This suggests a more complex role for vmPFC than current theories suggest, specifically regarding context-specific behavioral optimization.
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63
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Hofmann SG, Hay AC. Rethinking avoidance: Toward a balanced approach to avoidance in treating anxiety disorders. J Anxiety Disord 2018; 55:14-21. [PMID: 29550689 PMCID: PMC5879019 DOI: 10.1016/j.janxdis.2018.03.004] [Citation(s) in RCA: 115] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 03/07/2018] [Accepted: 03/07/2018] [Indexed: 12/31/2022]
Abstract
Avoidance is typically considered a maladaptive behavioral response to excessive fear and anxiety, leading to the maintenance of anxiety disorders. Exposure is a core element of cognitive-behavioral therapy for anxiety disorders. One important aspect of this treatment is repeated and prolonged exposure to a threat while discouraging patients from using avoidance strategies, such as escape or safety behaviors. We will first revisit the role of avoidance learning in the development and maintenance of anxiety disorders, including important insights from the neuroscience literature. Next, we will consider both the negative and positive aspects of avoidance for therapeutic interventions. Finally, we will explore the application of adaptive avoidance in exposure therapy for anxiety disorders. We will argue that there are occasions when avoidance behaviors can serve as effective coping strategies to enhance the person's perception of control over the environment and the potential threat. We conclude that avoidance behaviors can be a valuable therapeutic element, depending on the function of these behaviors.
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Affiliation(s)
- Stefan G Hofmann
- Boston University, Department of Psychological and Brain Sciences, 648 Beacon St., 6(th) Floor, Boston, MA, 02215, USA.
| | - Aleena C Hay
- Boston University, Department of Psychological and Brain Sciences, 648 Beacon St., 6(th) Floor, Boston, MA, 02215, USA
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64
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Grunfeld IS, Likhtik E. Mixed selectivity encoding and action selection in the prefrontal cortex during threat assessment. Curr Opin Neurobiol 2018; 49:108-115. [PMID: 29454957 PMCID: PMC5889962 DOI: 10.1016/j.conb.2018.01.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 12/27/2017] [Accepted: 01/17/2018] [Indexed: 01/18/2023]
Abstract
The medial prefrontal cortex (mPFC) regulates expression of emotional behavior. The mPFC combines multivariate information from its inputs, and depending on the imminence of threat, activates downstream networks that either increase or decrease the expression of anxiety-related motor behavior and autonomic activation. Here, we selectively highlight how subcortical input to the mPFC from two example structures, the amygdala and ventral hippocampus, help shape mixed selectivity encoding and action selection during emotional processing. We outline a model where prefrontal subregions modulate behavior along orthogonal motor dimensions, and exhibit connectivity that selects for expression of one behavioral strategy while inhibiting the other.
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Affiliation(s)
- Itamar S Grunfeld
- Biology Department, Hunter College, CUNY, United States; Neuroscience Collaborative, The Graduate Center, CUNY, United States
| | - Ekaterina Likhtik
- Biology Department, Hunter College, CUNY, United States; Neuroscience Collaborative, The Graduate Center, CUNY, United States.
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65
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LeDoux J, Daw ND. Surviving threats: neural circuit and computational implications of a new taxonomy of defensive behaviour. Nat Rev Neurosci 2018; 19:269-282. [PMID: 29593300 DOI: 10.1038/nrn.2018.22] [Citation(s) in RCA: 199] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Research on defensive behaviour in mammals has in recent years focused on elicited reactions; however, organisms also make active choices when responding to danger. We propose a hierarchical taxonomy of defensive behaviour on the basis of known psychological processes. Included are three categories of reactions (reflexes, fixed reactions and habits) and three categories of goal-directed actions (direct action-outcome behaviours and actions based on implicit or explicit forecasting of outcomes). We then use this taxonomy to guide a summary of findings regarding the underlying neural circuits.
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Affiliation(s)
- Joseph LeDoux
- Center for Neural Science and Department of Psychology, New York University, New York, NY, USA.,Department of Psychiatry and Department of Child and Adolescent Psychiatry, New York University Langone Medical School, New York, NY, USA.,Nathan Kline Institute for Psychiatry Research, Orangeburg, NY, USA
| | - Nathaniel D Daw
- Princeton Neuroscience Institute and Department of Psychology, Princeton University, Princeton, NJ, USA
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66
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Strigo IA, Spadoni AD, Inslicht SS, Simmons AN. Repeated Exposure to Experimental Pain Differentiates Combat Traumatic Brain Injury with and without Post-Traumatic Stress Disorder. J Neurotrauma 2017; 35:297-307. [PMID: 28931334 DOI: 10.1089/neu.2017.5061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD) are highly comorbid conditions that often co-occur with chronic pain. We have shown that women with PTSD subsequent to intimate partner violence show attenuated brain response to repeated experimental pain that was related to symptoms of avoidance. The aim of this study was to extend our past findings to males with combat trauma and to examine brain response to experimental pain in men with and without PTSD who sustained mTBI during combat. Seventy male veterans performed an experimental pain paradigm during functional magnetic resonance imaging fMRI. Of the 70 total subjects, 46 self-reported a history of mTBI during combat (46 of 70). Of those with mTBI, 26 also met criteria for PTSD (26 of 46). As in our previous study, we examined change in brain activity to repeated heat pain with linear mixed-effects modeling for group by administration interaction effects. We observed a significant group by administration interaction to repeated heat pain within insular, frontal, and parietal cortices, such that the control group showed increased activation over time, whereas mTBI groups (mTBI-only, mTBI + PTSD) showed decreased activation within bilateral anterior insulas (AIs) between administrations. Importantly, change in the right AI response was inversely correlated with avoidance symptoms, but only in those with comorbid mTBI + PTSD. Further, in the comorbid group, greater AI attenuation was associated with decreased connectivity with anterior cingulate (ACC). The current study provides further evidence that repeated exposure to brief painful stimuli results in attenuation of insula activation over time in traumatized individuals. Further, in PTSD, AI shows greatest attenuation in those with the highest level of avoidance-a finding that was replicated across diverse samples. Thus, this mechanism may be a generalized mechanism of maladaptive response to experimental pain in those with significant trauma.
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Affiliation(s)
- Irina A Strigo
- 1 Veterans Affairs San Francisco Healthcare System , San Francisco, California.,2 University of California San Francisco , San Francisco, California
| | - Andrea D Spadoni
- 3 Veterans Affairs San Diego Healthcare System , San Diego, California.,4 University of California , San Diego, La Jolla, California
| | - Sabra S Inslicht
- 1 Veterans Affairs San Francisco Healthcare System , San Francisco, California.,2 University of California San Francisco , San Francisco, California
| | - Alan N Simmons
- 3 Veterans Affairs San Diego Healthcare System , San Diego, California.,4 University of California , San Diego, La Jolla, California
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67
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Vervliet B, Lange I, Milad MR. Temporal dynamics of relief in avoidance conditioning and fear extinction: Experimental validation and clinical relevance. Behav Res Ther 2017; 96:66-78. [DOI: 10.1016/j.brat.2017.04.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 04/18/2017] [Accepted: 04/20/2017] [Indexed: 11/30/2022]
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68
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Treanor M, Barry TJ. Treatment of avoidance behavior as an adjunct to exposure therapy: Insights from modern learning theory. Behav Res Ther 2017; 96:30-36. [DOI: 10.1016/j.brat.2017.04.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 04/11/2017] [Accepted: 04/17/2017] [Indexed: 10/19/2022]
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Avoidant Responses to Interpersonal Provocation Are Associated with Increased Amygdala and Decreased Mentalizing Network Activity. eNeuro 2017; 4:eN-NWR-0337-16. [PMID: 28660251 PMCID: PMC5485378 DOI: 10.1523/eneuro.0337-16.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 05/19/2017] [Accepted: 06/06/2017] [Indexed: 12/30/2022] Open
Abstract
When intentionally pushed or insulted, one can either flee from the provoker or retaliate. The implementation of such fight-or-flight decisions is a central aspect in the genesis and evolution of aggression episodes, yet it is usually investigated only indirectly or in nonsocial situations. In the present fMRI study, we aimed to distinguish brain regions associated with aggressive and avoidant responses to interpersonal provocation in humans. Participants (thirty-six healthy young women) could either avoid or face a highly (HP) and a lowly (LP) provoking opponent in a competitive reaction time task: the fight-or-escape (FOE) paradigm. Subjects avoided the HP more often, but retaliated when facing her. Moreover, they chose to fight the HP more quickly, and showed increased heart rate (HR) right before confronting her. Orbitofrontal cortex (OFC) and sensorimotor cortex were more active when participants decided to fight, whereas the mentalizing network was engaged when deciding to avoid. Importantly, avoiding the HP relative to the LP was associated with both higher activation in the right basolateral amygdala and lower relative activity in several mentalizing regions [e.g., medial and inferior frontal gyrus (IFG), temporal-parietal junction (TPJ)]. These results suggest that avoidant responses to provocation might result from heightened threat anticipation and are associated with reduced perspective taking. Furthermore, our study helps to reconcile conflicting findings on the role of the mentalizing network, the amygdala, and the OFC in aggression.
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70
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Paré D, Quirk GJ. WHEN SCIENTIFIC PARADIGMS LEAD TO TUNNEL VISION: LESSONS FROM THE STUDY OF FEAR. NPJ SCIENCE OF LEARNING 2017; 2:6. [PMID: 30294453 PMCID: PMC6171770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/07/2017] [Accepted: 02/21/2017] [Indexed: 10/05/2023]
Abstract
For the past 30 years, research on the amygdala has largely focused on the genesis of defensive behaviors as its main function. This focus originated from early lesion studies and was supported by extensive anatomical, physiological, and pharmacological data. Here we argue that while much data is consistent with the fear model of amygdala function, it has never been directly tested, in part due to overreliance on the fear conditioning task. In support of the fear model, amygdala neurons appear to signal threats and/or stimuli predictive of threats. However, recent studies in a natural threat setting show that amygdala activity does not correlate with threats, but simply with the movement of the rat, independent of valence. This was true for both natural threats as well as conditioned stimuli; indeed there was no evidence of threat signaling in amygdala neurons. Similar findings are emerging for prefrontal neurons that modulate the amygdala. These recent developments lead us to propose a new conceptualization of amygdala function whereby the amygdala inhibits behavioral engagement. Moreover, we propose that the goal of understanding the amygdala will be best served by shifting away from fear conditioning toward naturalistic approach and avoidance paradigms that involve decision making and a larger repertoire of spontaneous and learned behaviors, all the while keeping an open mind.
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Affiliation(s)
- Denis Paré
- Center for Molecular and Behavioral Neuroscience, Rutgers State University, Newark, NJ 07102 USA
| | - Gregory J. Quirk
- University of Puerto Rico School of Medicine, San Juan, PR 00936-5067 USA
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71
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Paré D, Quirk GJ. WHEN SCIENTIFIC PARADIGMS LEAD TO TUNNEL VISION: LESSONS FROM THE STUDY OF FEAR. NPJ SCIENCE OF LEARNING 2017; 2:6. [PMID: 30294453 PMCID: PMC6171770 DOI: 10.1038/s41539-017-0007-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/07/2017] [Accepted: 02/21/2017] [Indexed: 06/08/2023]
Abstract
For the past 30 years, research on the amygdala has largely focused on the genesis of defensive behaviors as its main function. This focus originated from early lesion studies and was supported by extensive anatomical, physiological, and pharmacological data. Here we argue that while much data is consistent with the fear model of amygdala function, it has never been directly tested, in part due to overreliance on the fear conditioning task. In support of the fear model, amygdala neurons appear to signal threats and/or stimuli predictive of threats. However, recent studies in a natural threat setting show that amygdala activity does not correlate with threats, but simply with the movement of the rat, independent of valence. This was true for both natural threats as well as conditioned stimuli; indeed there was no evidence of threat signaling in amygdala neurons. Similar findings are emerging for prefrontal neurons that modulate the amygdala. These recent developments lead us to propose a new conceptualization of amygdala function whereby the amygdala inhibits behavioral engagement. Moreover, we propose that the goal of understanding the amygdala will be best served by shifting away from fear conditioning toward naturalistic approach and avoidance paradigms that involve decision making and a larger repertoire of spontaneous and learned behaviors, all the while keeping an open mind.
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Affiliation(s)
- Denis Paré
- Center for Molecular and Behavioral Neuroscience, Rutgers State University, Newark, NJ 07102 USA
| | - Gregory J. Quirk
- University of Puerto Rico School of Medicine, San Juan, PR 00936-5067 USA
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72
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LeDoux JE, Moscarello J, Sears R, Campese V. The birth, death and resurrection of avoidance: a reconceptualization of a troubled paradigm. Mol Psychiatry 2017; 22:24-36. [PMID: 27752080 PMCID: PMC5173426 DOI: 10.1038/mp.2016.166] [Citation(s) in RCA: 210] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 08/03/2016] [Accepted: 08/11/2016] [Indexed: 12/28/2022]
Abstract
Research on avoidance conditioning began in the late 1930s as a way to use laboratory experiments to better understand uncontrollable fear and anxiety. Avoidance was initially conceived of as a two-factor learning process in which fear is first acquired through Pavlovian aversive conditioning (so-called fear conditioning), and then behaviors that reduce the fear aroused by the Pavlovian conditioned stimulus are reinforced through instrumental conditioning. Over the years, criticisms of both the avoidance paradigm and the two-factor fear theory arose. By the mid-1980s, avoidance had fallen out of favor as an experimental model relevant to fear and anxiety. However, recent progress in understanding the neural basis of Pavlovian conditioning has stimulated a new wave of research on avoidance. This new work has fostered new insights into contributions of not only Pavlovian and instrumental learning but also habit learning, to avoidance, and has suggested that the reinforcing event underlying the instrumental phase should be conceived in terms of cellular and molecular events in specific circuits rather than in terms of vague notions of fear reduction. In our approach, defensive reactions (freezing), actions (avoidance) and habits (habitual avoidance) are viewed as being controlled by unique circuits that operate nonconsciously in the control of behavior, and that are distinct from the circuits that give rise to conscious feelings of fear and anxiety. These refinements, we suggest, overcome older criticisms, justifying the value of the new wave of research on avoidance, and offering a fresh perspective on the clinical implications of this work.
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Affiliation(s)
- J E LeDoux
- Center for Neural Science, New York University, New York, NY, USA
- Nathan Kline Institute, Orangeburg, NY, USA
| | - J Moscarello
- Center for Neural Science, New York University, New York, NY, USA
| | - R Sears
- Center for Neural Science, New York University, New York, NY, USA
| | - V Campese
- Center for Neural Science, New York University, New York, NY, USA
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73
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Rodriguez-Romaguera J, Greenberg BD, Rasmussen SA, Quirk GJ. An Avoidance-Based Rodent Model of Exposure With Response Prevention Therapy for Obsessive-Compulsive Disorder. Biol Psychiatry 2016; 80:534-40. [PMID: 27086546 PMCID: PMC4988932 DOI: 10.1016/j.biopsych.2016.02.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 01/30/2016] [Accepted: 02/11/2016] [Indexed: 10/22/2022]
Abstract
BACKGROUND Obsessive-compulsive disorder is treated with exposure with response prevention (ERP) therapy, in which patients are repeatedly exposed to compulsive triggers but prevented from expressing their compulsions. Many compulsions are an attempt to avoid perceived dangers, and the intent of ERP is to extinguish compulsions. Patients failing ERP therapy are candidates for deep brain stimulation (DBS) of the ventral capsule/ventral striatum, which facilitates patients' response to ERP therapy. An animal model of ERP would be useful for understanding the neural mechanisms of extinction in obsessive-compulsive disorder. METHODS Using a platform-mediated signaled avoidance task, we developed a rodent model of ERP called extinction with response prevention (Ext-RP), in which avoidance-conditioned rats are given extinction trials while blocking access to the avoidance platform. Following 3 days of Ext-RP, rats were tested with the platform unblocked to evaluate persistent avoidance. We then assessed if pharmacologic inactivation of lateral orbitofrontal cortex (lOFC) or DBS of the ventral striatum reduced persistent avoidance. RESULTS Following Ext-RP training, most rats showed reduced avoidance at test (Ext-RP success), but a subset persisted in their avoidance (Ext-RP failure). Pharmacologic inactivation of lOFC eliminated persistent avoidance, as did DBS applied to the ventral striatum during Ext-RP. CONCLUSIONS DBS of ventral striatum has been previously shown to inhibit lOFC activity. Thus, activity in lOFC, which is known to be hyperactive in obsessive-compulsive disorder, may be responsible for impairing patients' response to ERP therapy.
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Affiliation(s)
- Jose Rodriguez-Romaguera
- Departments of Psychiatry and Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, PR 00936
| | | | - Steven A. Rasmussen
- Department of Psychiatry and Human Behavior, Brown University, Providence, RI 02906
| | - Gregory J. Quirk
- Departments of Psychiatry and Anatomy & Neurobiology, University of Puerto Rico School of Medicine, San Juan, PR 00936
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Halladay LR, Blair HT. Prefrontal infralimbic cortex mediates competition between excitation and inhibition of body movements during pavlovian fear conditioning. J Neurosci Res 2016; 95:853-862. [PMID: 26997207 DOI: 10.1002/jnr.23736] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 02/29/2016] [Accepted: 02/29/2016] [Indexed: 01/21/2023]
Abstract
The infralimbic subregion of the prefrontal cortex (IL) is broadly involved in behavioral flexibility, risk assessment, and outcome reinforcement. In aversive conditioning tasks, the IL has been implicated in fear extinction and in mediating transitions between Pavlovian and instrumental responses. Here we examine the role of the IL in mediating transitions between two competing Pavlovian fear responses, conditioned motor inhibition (CMI) and conditioned motor excitation (CME). Rats were trained to fear an auditory conditioned stimulus (CS) by pairing it with periorbital shock to one eyelid (the unconditioned stimulus [US]). Trained animals exhibited CMI responses (movement suppression) to the CS when they had not recently encountered the US (>24 hr), but, after recent encounters with the US (<5 min), the CS evoked CME responses (turning in circles away from anticipated shock). Animals then received bilateral infusions of muscimol or picrotoxin to inactivate or hyperactivate the IL, respectively. Neither drug reliably affected CMI responses, but there was a bidirectional effect on CME responses; inactivation of the IL attenuated CME responses, whereas hyperactivation potentiated CME responses. These results provide evidence that activation of the IL may promote behavioral strategies that involve mobilizing the body and suppress strategies that involve immobilizing the body. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Lindsay R Halladay
- Department of Psychology, University of California Los Angeles, Los Angeles, California.,National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland
| | - Hugh T Blair
- Department of Psychology, University of California Los Angeles, Los Angeles, California
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Ahmadi-Mahmoodabadi N, Nasehi M, Emam Ghoreishi M, Zarrindast MR. Synergistic effect between prelimbic 5-HT3 and CB1 receptors on memory consolidation deficit in adult male Sprague–Dawley rats: An isobologram analysis. Neuroscience 2016; 317:173-83. [DOI: 10.1016/j.neuroscience.2015.12.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 11/20/2015] [Accepted: 12/07/2015] [Indexed: 10/22/2022]
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Campese VD, Sears RM, Moscarello JM, Diaz-Mataix L, Cain CK, LeDoux JE. The Neural Foundations of Reaction and Action in Aversive Motivation. Curr Top Behav Neurosci 2016; 27:171-195. [PMID: 26643998 DOI: 10.1007/7854_2015_401] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Much of the early research in aversive learning concerned motivation and reinforcement in avoidance conditioning and related paradigms. When the field transitioned toward the focus on Pavlovian threat conditioning in isolation, this paved the way for the clear understanding of the psychological principles and neural and molecular mechanisms responsible for this type of learning and memory that has unfolded over recent decades. Currently, avoidance conditioning is being revisited, and with what has been learned about associative aversive learning, rapid progress is being made. We review, below, the literature on the neural substrates critical for learning in instrumental active avoidance tasks and conditioned aversive motivation.
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Affiliation(s)
| | - Robert M Sears
- Emotional Brain Institute at NYU and Nathan Kline Institute, New York, USA
| | | | | | - Christopher K Cain
- Emotional Brain Institute at NYU and Nathan Kline Institute, New York, USA
| | - Joseph E LeDoux
- Center for Neural Science, NYU, New York, USA
- Emotional Brain Institute at NYU and Nathan Kline Institute, New York, USA
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Vervliet B, Indekeu E. Low-Cost Avoidance Behaviors are Resistant to Fear Extinction in Humans. Front Behav Neurosci 2015; 9:351. [PMID: 26733837 PMCID: PMC4689807 DOI: 10.3389/fnbeh.2015.00351] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 12/03/2015] [Indexed: 12/01/2022] Open
Abstract
Elevated levels of fear and avoidance are core symptoms across the anxiety disorders. It has long been known that fear serves to motivate avoidance. Consequently, fear extinction has been the primary focus in pre-clinical anxiety research for decades, under the implicit assumption that removing the motivator of avoidance (fear) would automatically mitigate the avoidance behaviors as well. Although this assumption has intuitive appeal, it has received little scientific scrutiny. The scarce evidence from animal studies is mixed, while the assumption remains untested in humans. The current study applied an avoidance conditioning protocol in humans to investigate the effects of fear extinction on the persistence of low-cost avoidance. Online danger-safety ratings and skin conductance responses documented the dynamics of conditioned fear across avoidance and extinction phases. Anxiety- and avoidance-related questionnaires explored individual differences in rates of avoidance. Participants first learned to click a button during a predictive danger signal, in order to cancel an upcoming aversive electrical shock (avoidance conditioning). Next, fear extinction was induced by presenting the signal in the absence of shocks while button-clicks were prevented (by removing the button in Experiment 1, or by instructing not to click the button in Experiment 2). Most importantly, post-extinction availability of the button caused a significant return of avoidant button-clicks. In addition, trait-anxiety levels correlated positively with rates of avoidance during a predictive safety signal, and with the rate of pre- to post-extinction decrease during this signal. Fear measures gradually decreased during avoidance conditioning, as participants learned that button-clicks effectively canceled the shock. Preventing button-clicks elicited a sharp increase in fear, which subsequently extinguished. Fear remained low during avoidance testing, but danger-safety ratings increased again when button-clicks were subsequently prevented. Together, these results show that low-cost avoidance behaviors can persist following fear extinction and induce increased threat appraisal. On the other hand, fear extinction did reduce augmented rates of unnecessary avoidance during safety in trait-anxious individuals, and instruction-based response prevention was more effective than removal of response cues. More research is needed to characterize the conditions under which fear extinction might mitigate avoidance.
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Affiliation(s)
- Bram Vervliet
- Department of Psychiatry, Massachusetts General Hospital and Harvard Medical SchoolBoston, MA, USA; Center for Excellence on Generalization in Health and Psychopathology, University of Leuven-KU LeuvenLeuven, Belgium
| | - Ellen Indekeu
- Department of Psychology, University of Leuven-KU Leuven Leuven, Belgium
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Abstract
RATIONALE There is a high degree of comorbidity between alcohol use disorder and post-traumatic stress disorder (PTSD), but little is known about the interactions of ethanol with traumatic memories. OBJECTIVES Using auditory fear conditioning in rats, we asked if repeated exposure to ethanol could modify the retrieval of fear memories acquired prior to ethanol exposure. METHODS Following auditory fear conditioning, Sprague-Dawley rats were given daily injections of ethanol (1.5 g/kg) or saline over 5 days. Two days later, they were given 20 trials of extinction training and then tested for extinction memory the following day. In a separate experiment, conditioned rats were given repeated ethanol injections and processed for c-Fos immunohistochemistry following a fear retrieval session. RESULTS Two days following the cessation of ethanol, the magnitude of conditioned fear responses (freezing and suppression of bar pressing) was significantly increased. This increase persisted the following day. Waiting 10 days following cessation of ethanol eliminated the effect on fear retrieval. In rats conditioned with low shock levels, repeated exposure to ethanol converted a sub-threshold fear memory into a supra-threshold fear memory. It also increased c-Fos expression in the prelimbic prefrontal cortex, paraventricular thalamus, and the central and basolateral nuclei of the amygdala, areas implicated in the retrieval of fear memories. CONCLUSIONS These results suggest that repeated exposure to ethanol may exacerbate pre-existing traumatic memories.
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