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Fry BR, Roberts D, Thakkar KN, Johnson AW. Variables influencing conditioning-evoked hallucinations: overview and future applications. Psychol Med 2022; 52:2937-2949. [PMID: 36138518 PMCID: PMC9693682 DOI: 10.1017/s0033291722002100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 06/13/2022] [Accepted: 06/20/2022] [Indexed: 01/05/2023]
Abstract
Hallucinations occur in the absence of sensory stimulation and result in vivid perceptual experiences of nonexistent events that manifest across a range of sensory modalities. Approaches from the field of experimental and cognitive psychology have leveraged the idea that associative learning experiences can evoke conditioning-induced hallucinations in both animals and humans. In this review, we describe classical and contemporary findings and highlight the variables eliciting these experiences. We also provide an overview of the neurobiological mechanisms, along with the associative and computational factors that may explain hallucinations that are generated by representation-mediated conditioning phenomena. Through the integration of animal and human research, significant advances into the psychobiology of hallucinations are possible, which may ultimately translate to more effective clinical applications.
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Affiliation(s)
- Benjamin R. Fry
- Department of Psychology, Michigan State University, East Lansing, MI, USA
| | - Dominic Roberts
- Department of Psychology, Michigan State University, East Lansing, MI, USA
| | - Katharine N. Thakkar
- Department of Psychology, Michigan State University, East Lansing, MI, USA
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Alexander W. Johnson
- Department of Psychology, Michigan State University, East Lansing, MI, USA
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
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2
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Fleming LM, Jaynes FJB, Thompson SL, Corlett PR, Taylor JR. Targeted effects of ketamine on perceptual expectation during mediated learning in rats. Psychopharmacology (Berl) 2022; 239:2395-2405. [PMID: 35389087 PMCID: PMC9296571 DOI: 10.1007/s00213-022-06128-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 03/26/2022] [Indexed: 10/18/2022]
Abstract
RATIONALE While neural correlates of hallucinations are known, the mechanisms have remained elusive. Mechanistic insight is more practicable in animal models, in which causal relationships can be established. Recent work developing animal models of hallucination susceptibility has focused on the genesis of perceptual expectations and perceptual decision-making. Both processes are encompassed within mediated learning, which involves inducing a strong perceptual expectation via associative learning, retrieving that memory representation, and deciding whether this internally generated percept is predictive of an external outcome. Mediated learning in rodents is sensitive to many psychotomimetic manipulations. However, we do not know if these manipulations selectively alter learning of perceptual expectations versus their retrieval because of their presence throughout all task phases. OBJECTIVES Here, we used mediated learning to study the targeted effect of a psychotomimetic agent on the retrieval of perceptual expectation. METHODS We administered (R,S)-ketamine to rats selectively during the devaluation phase of a mediated learning task, when the representation of the expected cue is retrieved, to test the hypothesis that internally generated perceptual experiences underlie this altered mediated learning. RESULTS We found that ketamine increased only mediated learning at a moderate dose in rats, but impaired direct learning at the high dose. CONCLUSIONS These results suggest that ketamine can augment retrieval of perceptual expectations and thus this may be how it induces hallucination-like experiences in humans. More broadly, mediated learning may unite the conditioning, perceptual decision-making, and even reality monitoring accounts of psychosis in a manner that translates across species.
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Affiliation(s)
- Leah M Fleming
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT, USA
| | - Frances-Julia B Jaynes
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Department of Psychology, University of New Haven, New Haven, CT, USA
- Department of Psychiatry, University of Connecticut Health, Farmington, CT, USA
| | - Summer L Thompson
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Philip R Corlett
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Department of Psychology, Yale University, New Haven, CT, USA
| | - Jane R Taylor
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA.
- Department of Psychology, Yale University, New Haven, CT, USA.
- Department of Neuroscience, Yale University, New Haven, CT, USA.
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Rootes-Murdy K, Goldsmith DR, Turner JA. Clinical and Structural Differences in Delusions Across Diagnoses: A Systematic Review. Front Integr Neurosci 2022; 15:726321. [PMID: 35140591 PMCID: PMC8818879 DOI: 10.3389/fnint.2021.726321] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 12/16/2021] [Indexed: 12/18/2022] Open
Abstract
Delusions are marked, fixed beliefs that are incongruent with reality. Delusions, with comorbid hallucinations, are a hallmark of certain psychotic disorders (e.g., schizophrenia). Delusions can present transdiagnostically, in neurodegenerative (e.g., Alzheimer's disease and fronto-temporal dementia), nervous system disorders (e.g., Parkinson's disease) and across other psychiatric disorders (e.g., bipolar disorder). The burden of delusions is severe and understanding the heterogeneity of delusions may delineate a more valid nosology of not only psychiatric disorders but also neurodegenerative and nervous system disorders. We systematically reviewed structural neuroimaging studies reporting on delusions in four disorder types [schizophrenia (SZ), bipolar disorder (BP), Alzheimer's disease (AD), and Parkinson's disease (PD)] to provide a comprehensive overview of neural changes and clinical presentations associated with delusions. Twenty-eight eligible studies were identified. This review found delusions were most associated with gray matter reductions in the dorsolateral prefrontal cortex (SZ, BP, and AD), left claustrum (SZ and AD), hippocampus (SZ and AD), insula (SZ, BP, and AD), amygdala (SZ and BP), thalamus (SZ and AD), superior temporal gyrus (SZ, BP, and AD), and middle frontal gyrus (SZ, BP, AD, and PD). However, there was a great deal of variability in the findings of each disorder. There is some support for the current dopaminergic hypothesis of psychosis, but we also propose new hypotheses related to the belief formation network and cognitive biases. We also propose a standardization of assessments to aid future transdiagnostic study approaches. Future studies should explore the neural and biological underpinnings of delusions to hopefully, inform future treatment.
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Affiliation(s)
- Kelly Rootes-Murdy
- Department of Psychology, Georgia State University, Atlanta, GA, United States
- Tri-institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
- *Correspondence: Kelly Rootes-Murdy
| | - David R. Goldsmith
- Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, United States
| | - Jessica A. Turner
- Department of Psychology, Georgia State University, Atlanta, GA, United States
- Tri-institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
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Fam J, Clemens KJ, Westbrook RF, Morris MJ, Kendig MD. Chronic exposure to cafeteria-style diet in rats alters sweet taste preference and reduces motivation for, but not 'liking' of sucrose. Appetite 2022; 168:105742. [PMID: 34634373 DOI: 10.1016/j.appet.2021.105742] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 10/07/2021] [Accepted: 10/07/2021] [Indexed: 12/27/2022]
Abstract
Obesity is associated with changes to taste perception and brain reward circuitry. It is important to understand how these effects alter the preference for palatable foods and drinks, given that these are widely consumed, and leading risk factors for obesity. This study examined the effects of diet-induced obesity on sweet taste preference by analysing the microstructure of licking for sugar solutions and assessing pERK expression in the nucleus accumbens shell and insula. Adult male Sprague-Dawley rats were fed standard chow (Control; n = 16) or a varied, palatable cafeteria diet (Caf; n = 16) for 12 weeks. Two-choice preference tests between 2%, 8% and 32% sucrose solutions were conducted at baseline and in weeks 11-12 of the diet. Rats in the Caf group trebled energy intake and doubled weight gain relative to controls. In tests held under water restriction after 11 weeks of diet, the Control group reliably preferred higher sucrose concentrations (i.e., 32% > 8% > 2%). Relative to controls, the Caf group showed a stronger preference for 32% vs. 2% sucrose, lower preference for 32% vs. 8% sucrose, and were indifferent to 8% vs. 2% sucrose. Testing without water restriction increased preference for higher sucrose concentrations in both groups. Chronic Caf diet increased the latency to lick, decreased total licks and reduced alternations between spouts, but did not alter lick cluster size, a measure of hedonic appraisal, on any test. Following a final exposure to a novel sucrose concentration, neuronal activity (pERK) in the insula and nucleus accumbens shell was significantly reduced in the Caf group. Results indicate that differences in 'liking' do not underlie obesity-induced changes to sweet taste preference.
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Affiliation(s)
- Justine Fam
- School of Psychology, UNSW Sydney, NSW, 2052, Australia
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Guerrin CGJ, Doorduin J, Sommer IE, de Vries EFJ. The dual hit hypothesis of schizophrenia: Evidence from animal models. Neurosci Biobehav Rev 2021; 131:1150-1168. [PMID: 34715148 DOI: 10.1016/j.neubiorev.2021.10.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 10/21/2021] [Accepted: 10/24/2021] [Indexed: 12/16/2022]
Abstract
Schizophrenia is a heterogeneous psychiatric disorder, which can severely impact social and professional functioning. Epidemiological and clinical studies show that schizophrenia has a multifactorial aetiology comprising genetic and environmental risk factors. Although several risk factors have been identified, it is still not clear how they result in schizophrenia. This knowledge gap, however, can be investigated in animal studies. In this review, we summarise animal studies regarding molecular and cellular mechanisms through which genetic and environmental factors may affect brain development, ultimately causing schizophrenia. Preclinical studies suggest that early environmental risk factors can affect the immune, GABAergic, glutamatergic, or dopaminergic system and thus increase the susceptibility to another risk factor later in life. A second insult, like social isolation, stress, or drug abuse, can further disrupt these systems and the interactions between them, leading to behavioural abnormalities. Surprisingly, first insults like maternal infection and early maternal separation can also have protective effects. Single gene mutations associated with schizophrenia did not have a major impact on the susceptibility to subsequent environmental hits.
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Affiliation(s)
- Cyprien G J Guerrin
- Department of Nuclear Medicine and Medical Imaging, University of Groningen, University Medical Centre Groningen, Hanzeplein 1, 9713, GZ, Groningen, the Netherlands
| | - Janine Doorduin
- Department of Nuclear Medicine and Medical Imaging, University of Groningen, University Medical Centre Groningen, Hanzeplein 1, 9713, GZ, Groningen, the Netherlands
| | - Iris E Sommer
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713, GZ, Groningen, the Netherlands
| | - Erik F J de Vries
- Department of Nuclear Medicine and Medical Imaging, University of Groningen, University Medical Centre Groningen, Hanzeplein 1, 9713, GZ, Groningen, the Netherlands.
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Ioannidou C, Busquets-Garcia A, Ferreira G, Marsicano G. Neural Substrates of Incidental Associations and Mediated Learning: The Role of Cannabinoid Receptors. Front Behav Neurosci 2021; 15:722796. [PMID: 34421557 PMCID: PMC8378742 DOI: 10.3389/fnbeh.2021.722796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 07/14/2021] [Indexed: 11/13/2022] Open
Abstract
The ability to form associations between different stimuli in the environment to guide adaptive behavior is a central element of learning processes, from perceptual learning in humans to Pavlovian conditioning in animals. Like so, classical conditioning paradigms that test direct associations between low salience sensory stimuli and high salience motivational reinforcers are extremely informative. However, a large part of everyday learning cannot be solely explained by direct conditioning mechanisms - this includes to a great extent associations between individual sensory stimuli, carrying low or null immediate motivational value. This type of associative learning is often described as incidental learning and can be captured in animal models through sensory preconditioning procedures. Here we summarize the evolution of research on incidental and mediated learning, overview the brain systems involved and describe evidence for the role of cannabinoid receptors in such higher-order learning tasks. This evidence favors a number of contemporary hypotheses concerning the participation of the endocannabinoid system in psychosis and psychotic experiences and provides a conceptual framework for understanding how the use of cannabinoid drugs can lead to altered perceptive states.
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Affiliation(s)
- Christina Ioannidou
- INSERM, U1215 Neurocentre Magendie, Bordeaux, France
- University of Bordeaux, Bordeaux, France
| | - Arnau Busquets-Garcia
- Integrative Pharmacology and Systems Neuroscience Research Group, Neurosciences Research Program, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain
| | - Guillaume Ferreira
- University of Bordeaux, Bordeaux, France
- INRAE, Nutrition and Integrative Neurobiology, Bordeaux, France
| | - Giovanni Marsicano
- INSERM, U1215 Neurocentre Magendie, Bordeaux, France
- University of Bordeaux, Bordeaux, France
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Koh MT, Gallagher M. Using internal memory representations in associative learning to study hallucination-like phenomenon. Neurobiol Learn Mem 2020; 175:107319. [PMID: 33010386 PMCID: PMC7655598 DOI: 10.1016/j.nlm.2020.107319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/24/2020] [Accepted: 09/27/2020] [Indexed: 12/23/2022]
Abstract
Studies of Pavlovian conditioning have enriched our understanding of how relations among events can adaptively guide behavior through the formation and use of internal mental representations. In this review, we illustrate how internal representations flexibly integrate new updated information in reinforcer revaluation to influence relationships to impact actions and outcomes. We highlight representation-mediated learning to show the similarities in properties and functions between internally generated and directly activated representations, and how normal perception of internal representations could contribute to hallucinations. Converging evidence emerges from recent behavioral and neural activation studies using animal models of schizophrenia as well as clinical studies in patients to support increased tendencies in these populations to evoke internal representations from prior associative experience that approximate hallucination-like percepts. The heightened propensity is dependent on dopaminergic activation which is known to be sensitive to hippocampal overexcitability, a condition that has been observed in patients with psychosis. This presents a network that overlaps with cognitive neural circuits and offers a fresh approach for the development of therapeutic interventions targeting psychosis.
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Affiliation(s)
- Ming Teng Koh
- Department of Psychological and Brain Sciences, Johns Hopkins University, USA.
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, USA
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8
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Wu JL, Haberman RP, Gallagher M, Koh MT. Probing for Conditioned Hallucinations Through Neural Activation in a Ketamine Mouse Model of Schizophrenia. Neurosci Bull 2020; 36:937-941. [PMID: 32367251 PMCID: PMC7410946 DOI: 10.1007/s12264-020-00507-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Accepted: 01/31/2020] [Indexed: 11/26/2022] Open
Affiliation(s)
- Jenny L Wu
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Rebecca P Haberman
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Ming Teng Koh
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA.
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