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Alfieri V, Mattera A, Baldassarre G. Neural Circuits Underlying Social Fear in Rodents: An Integrative Computational Model. Front Syst Neurosci 2022; 16:841085. [PMID: 35350477 PMCID: PMC8957808 DOI: 10.3389/fnsys.2022.841085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 02/11/2022] [Indexed: 11/13/2022] Open
Abstract
Social avoidance in rodents arises from a complex interplay between the prefrontal cortex and subcortical structures, such as the ventromedial hypothalamus and the dorsal periaqueductal gray matter. Experimental studies are revealing the contribution of these areas, but an integrative view and model of how they interact to produce adaptive behavior are still lacking. Here, we present a computational model of social avoidance, proposing a set of integrated hypotheses on the possible macro organization of the brain system underlying this phenomenon. The model is validated by accounting for several different empirical findings and produces predictions to be tested in future experiments.
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Gunduz-Cinar O. The endocannabinoid system in the amygdala and modulation of fear. Prog Neuropsychopharmacol Biol Psychiatry 2021; 105:110116. [PMID: 32976951 PMCID: PMC7511205 DOI: 10.1016/j.pnpbp.2020.110116] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/07/2020] [Accepted: 09/20/2020] [Indexed: 01/01/2023]
Abstract
Posttraumatic stress disorder (PTSD) is a persistent, trauma induced psychiatric condition characterized by lifelong complex cognitive, emotional and behavioral phenotype. Although many individuals that experience trauma are able to gradually diminish their emotional responding to trauma-related stimuli over time, known as extinction learning, individuals suffering from PTSD are impaired in this capacity. An inability to decline this initially normal and adaptive fear response, can be confronted with exposure-based therapies, often in combination with pharmacological treatments. Due to the complexity of PTSD, currently available pharmacotherapeutics are inadequate in treating the deficient extinction observed in many PTSD patients. To develop novel therapeutics, researchers have exploited the conserved nature of fear and stress-associated behavioral responses and neurocircuits across species in an attempt to translate knowledge gained from preclinical studies into the clinic. There is growing evidence on the endocannabinoid modulation of fear and stress due to their 'on demand' synthesis and degradation. Involvement of the endocannabinoids in fear extinction makes the endocannabinoid system very attractive for finding effective therapeutics for trauma and stress related disorders. In this review, a brief introduction on neuroanatomy and circuitry of fear extinction will be provided as a model to study PTSD. Then, the endocannabinoid system will be discussed as an important component of extinction modulation. In this regard, anandamide degrading enzyme, fatty acid amide hydrolase (FAAH) will be exemplified as a target identified and validated strongly from preclinical to clinical translational studies of enhancing extinction.
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Affiliation(s)
- Ozge Gunduz-Cinar
- Laboratory of Behavioral and Genomic Neuroscience, National Institute on Alcoholism and Alcohol Abuse, NIH, Bethesda, MD, USA.
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Mattera A, Pagani M, Baldassarre G. A Computational Model Integrating Multiple Phenomena on Cued Fear Conditioning, Extinction, and Reinstatement. Front Syst Neurosci 2020; 14:569108. [PMID: 33132856 PMCID: PMC7550679 DOI: 10.3389/fnsys.2020.569108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/13/2020] [Indexed: 11/23/2022] Open
Abstract
Conditioning, extinction, and reinstatement are fundamental learning processes of animal adaptation, also strongly involved in human pathologies such as post-traumatic stress disorder, anxiety, depression, and dependencies. Cued fear conditioning, extinction, restatement, and systematic manipulations of the underlying brain amygdala and medial prefrontal cortex, represent key experimental paradigms to study such processes. Numerous empirical studies have revealed several aspects and the neural systems and plasticity underlying them, but at the moment we lack a comprehensive view. Here we propose a computational model based on firing rate leaky units that contributes to such integration by accounting for 25 different experiments on fear conditioning, extinction, and restatement, on the basis of a single neural architecture having a structure and plasticity grounded in known brain biology. This allows the model to furnish three novel contributions to understand these open issues: (a) the functioning of the central and lateral amygdala system supporting conditioning; (b) the role played by the endocannabinoids system in within- and between-session extinction; (c) the formation of three important types of neurons underlying fear processing, namely fear, extinction, and persistent neurons. The model integration of the results on fear conditioning goes substantially beyond what was done in previous models.
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Affiliation(s)
- Andrea Mattera
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome, Italy
| | - Marco Pagani
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome, Italy
| | - Gianluca Baldassarre
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome, Italy
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A model of amygdala function following plastic changes at specific synapses during extinction. Neurobiol Stress 2019; 10:100159. [PMID: 31193487 PMCID: PMC6535631 DOI: 10.1016/j.ynstr.2019.100159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 11/21/2022] Open
Abstract
The synaptic networks in the amygdala have been the subject of intense interest in recent times, primarily because of the role of this structure in emotion. Fear and its extinction depend on the workings of these networks, with particular interest in extinction because of its potential to ameliorate adverse symptoms associated with post-traumatic stress disorder. Here we place emphasis on the extinction networks revealed by recent techniques, and on the probable plasticity properties of their synaptic connections. We use modules of neurons representing each of the principal components identified as involved in extinction. Each of these modules consists of neural networks, containing specific ratios of excitatory and specialized inhibitory neurons as well as synaptic plasticity mechanisms appropriate for the component of the amygdala they represent. While these models can produce dynamic output, here we concentrate on the equilibrium outputs and do not model the details of the plasticity mechanisms. Pavlovian fear conditioning generates a fear memory in the lateral amygdala module that leads to activation of neurons in the basal nucleus fear module but not in the basal nucleus extinction module. Extinction protocols excite infralimbic medial prefrontal cortex neurons (IL) which in turn excite so-called extinction neurons in the amygdala, leading to the release of endocannabinoids from them and an increase in efficacy of synapses formed by lateral amygdala neurons on them. The model simulations show how such a mechanism could explain experimental observations involving the role of IL as well as endocannabinoids in different temporal phases of extinction.
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Bennett MR, Arnold J, Hatton SN, Lagopoulos J. Regulation of fear extinction by long-term depression: The roles of endocannabinoids and brain derived neurotrophic factor. Behav Brain Res 2016; 319:148-164. [PMID: 27867101 DOI: 10.1016/j.bbr.2016.11.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 11/10/2016] [Accepted: 11/15/2016] [Indexed: 11/19/2022]
Abstract
The extinction of a conditioned fear response is of great interest in the search for a means of ameliorating adverse neurobiological changes resulting from stress. The discovery that endocannibinoid (EC) levels are inversely related to the extent of such stress, and that the amygdala is a primary site mediating stress, suggests that ECs in this brain region might play a major role in extinction. Supporting this are the observations that the basolateral complex of the amygdala shows an increase in ECs only during extinction and that early clinical trials indicate that cannabinoid-like agents, when taken orally by patients suffering from post traumatic stress disorder (PTSD), reduce insomnia and nightmares. In order to optimize the potential of these agents to ameliorate symptoms of PTSD four important questions need to be answered: first, what is the identity of the cells that release ECs in the amygdala during extinction; second, what are their sites of action; third, what roles do the ECs play in the alleviation of long- depression (LTD), a process central to extinction; and finally, to what extent does brain derived neurotrophic factor (BDNF) facilitate the release of ECs? A review of the relevant literature is presented in an attempt to answer these questions. It is suggested that the principal cell involved in EC synthesis and release during extinction is the so-called excitatory extinction neuron in the basal nucleus of the amygdala. Furthermore that the main site of action of the ECs is the adjacent calcitonin gene-related peptide inhibitory interneurons, whose normal role of blocking the excitatory neurons is greatly diminished. The molecular pathways leading (during extinction trials) to the synthesis and release of ECs from synaptic spines of extinction neurons, that is potentiated by BDNF, are also delineated in this review. Finally, consideration is given to how the autocrine action of BDNF, linked to the release of ECs, can lead to the sustained release of these, so maintaining extinction over long times.
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Affiliation(s)
- Maxwell R Bennett
- The Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW, Australia.
| | - Jonathon Arnold
- The Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW, Australia
| | - Sean N Hatton
- The Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW, Australia
| | - Jim Lagopoulos
- The Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, NSW, Australia; The Sunshine Coast Mind and Neuroscience, Thompson Institute, The University of the Sunshine Coast, QLD, Australia
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Laricchiuta D, Saba L, De Bartolo P, Caioli S, Zona C, Petrosini L. Maintenance of aversive memories shown by fear extinction-impaired phenotypes is associated with increased activity in the amygdaloid-prefrontal circuit. Sci Rep 2016; 6:21205. [PMID: 26875790 PMCID: PMC4753413 DOI: 10.1038/srep21205] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 01/19/2016] [Indexed: 11/08/2022] Open
Abstract
Although aversive memory has been mainly addressed by analysing the changes occurring in average populations, the study of neuronal mechanisms of outliers allows understanding the involvement of individual differences in fear conditioning and extinction. We recently developed an innovative experimental model of individual differences in approach and avoidance behaviors, classifying the mice as Approaching, Balancing or Avoiding animals according to their responses to conflicting stimuli. The approach and avoidance behaviors appear to be the primary reactions to rewarding and threatening stimuli and may represent predictors of vulnerability (or resilience) to fear. We submitted the three mice phenotypes to Contextual Fear Conditioning. In comparison to Balancing animals, Approaching and Avoiding mice exhibited no middle- or long-term fear extinction. The two non-extinguishing phenotypes exhibited potentiated glutamatergic neurotransmission (spontaneous excitatory postsynaptic currents/spinogenesis) of pyramidal neurons of medial prefrontal cortex and basolateral amygdala. Basing on the a priori individuation of outliers, we demonstrated that the maintenance of aversive memories is linked to increased spinogenesis and excitatory signaling in the amygdala-prefrontal cortex fear matrix.
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Affiliation(s)
- Daniela Laricchiuta
- IRCCS Fondazione Santa Lucia, Rome, Italy
- Department of Psychology, University Sapienza of Rome, Rome, Italy
| | - Luana Saba
- IRCCS Fondazione Santa Lucia, Rome, Italy
- Department of Neuroscience, University of Rome “Tor Vergata”, Rome, Italy
| | - Paola De Bartolo
- IRCCS Fondazione Santa Lucia, Rome, Italy
- Department of Sociological and Psychopedagogical Studies, University Guglielmo Marconi of Rome, Rome, Italy
| | - Silvia Caioli
- IRCCS Fondazione Santa Lucia, Rome, Italy
- Department of Neuroscience, University of Rome “Tor Vergata”, Rome, Italy
| | - Cristina Zona
- IRCCS Fondazione Santa Lucia, Rome, Italy
- Department of Neuroscience, University of Rome “Tor Vergata”, Rome, Italy
| | - Laura Petrosini
- IRCCS Fondazione Santa Lucia, Rome, Italy
- Department of Psychology, University Sapienza of Rome, Rome, Italy
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The microinjection of a cannabinoid agonist into the accumbens shell induces anxiogenesis in the elevated plus-maze. Pharmacol Biochem Behav 2014; 124:160-6. [PMID: 24887448 DOI: 10.1016/j.pbb.2014.05.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 05/19/2014] [Accepted: 05/22/2014] [Indexed: 11/23/2022]
Abstract
This study investigated the effect of a cannabinoid agonist injected into the shell region of the nucleus accumbens (nAcb shell) on anxiety-related behaviors. The animals (male Wistar rats) were unilaterally microinjected with either ACEA (arachidonyl-2'-chloroethylamide a CB1 receptor agonist) at doses of 0.005, 0.05 or 0.5 pmol, or vehicle (ethanol 0.04% in saline 0.9%) and submitted to the elevated plus-maze (EPM), a pre-clinical test of anxiety. The data showed that rats microinjected with ACEA (0.05 pmol/0.2 μl) into the nAcb shell exhibited decreased % open arm time and open arm entries in comparison with the control group, which is compatible with an anxiogenic-like effect. To rule out the hypothesis that spread of the drug into the ventricle was responsible for the observed anxiogenic effect, 0.05 pmol ACEA was injected into the lateral ventricle and shown not to alter the responses representative of fear/anxiety and locomotion. The locomotor activity was not changed at the dose of 0.05 pmol ACEA microinjected into the nAcb shell. The present data suggest that activation of cannabinoid receptors in the nAcb shell may modulate fear/anxiety in the EPM.
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