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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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Nakamura T, Dinh TH, Asai M, Nishimaru H, Matsumoto J, Takamura Y, Hori E, Honda S, Yamada H, Mihara T, Matsumoto M, Nishijo H. Non-invasive electroencephalographical (EEG) recording system in awake monkeys. Heliyon 2020; 6:e04043. [PMID: 32490247 PMCID: PMC7260294 DOI: 10.1016/j.heliyon.2020.e04043] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/29/2019] [Accepted: 05/19/2020] [Indexed: 12/03/2022] Open
Abstract
Background Human clinical studies reported that several electroencephalographical (EEG) parameters can be used as biomarkers of psychiatric disorders. EEGs recorded from non-human primates (monkeys) is useful for understanding of human pathologies of psychiatric disorders and development of new therapeutic agents. New methods In this study, we expand a previous non-invasive head holding system with face masks for awake monkeys to be applied to scalp EEG recording. The new design of a head holding system allows to attach scalp EEG electrodes on the positions comparable to human electrode placement and to present auditory stimuli. Results With this system, we could record auditory evoked potentials (AEPs) in auditory sensory gating and oddball paradigms, which are often used as biomarkers of psychiatric disorders in animal models and human patients. The recorded AEPs were comparable to previous human clinical data. Comparison with existing methods Compared with previous non-invasive head holding systems, top, side (cheek and ears), and rear of the head can be open for attachment of EEG electrodes and auditory stimulation in the present system. Conclusions The results suggest that the present system is useful in EEG recording from awake monkeys. Furthermore, this system can be applied to eye-tracking and chronic intra-cerebral recording experiments.
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Affiliation(s)
- Tomoya Nakamura
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan.,Department of Anatomy, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Trong Ha Dinh
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Makoto Asai
- Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki 305-8585, Japan
| | - Hiroshi Nishimaru
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Jumpei Matsumoto
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Yusaku Takamura
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Etsuro Hori
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Sokichi Honda
- Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki 305-8585, Japan
| | - Hiroshi Yamada
- Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki 305-8585, Japan
| | - Takuma Mihara
- Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki 305-8585, Japan
| | - Mitsuyuki Matsumoto
- Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki 305-8585, Japan
| | - Hisao Nishijo
- System Emotional Science, Faculty of Medicine, University of Toyama, Toyama 930-0194, Japan
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You JC, Muralidharan K, Fu CH, Park J, Tosi U, Zhang X, Chin J. Distinct patterns of dentate gyrus cell activation distinguish physiologic from aberrant stimuli. PLoS One 2020; 15:e0232241. [PMID: 32407421 PMCID: PMC7224541 DOI: 10.1371/journal.pone.0232241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 04/10/2020] [Indexed: 11/20/2022] Open
Abstract
Under physiologic conditions, the dentate gyrus (DG) exhibits exceptionally low levels of activity compared to other brain regions. A sparse activation pattern is observed even when the DG is engaged to process new information; for example, only ~1–3% of neurons in the DG granule cell layer (GCL) are activated after placing animals in a novel, enriched environment. Moreover, such physiologic stimulation of GCL neurons recruits young granule cells more readily than older cells. This sparse pattern of cell activation has largely been attributed to intrinsic circuit properties of the DG, such as reduced threshold for activation in younger cells, and increased inhibition onto older cells. Given these intrinsic properties, we asked whether such activation of young granule cells was unique to physiologic stimulation, or could be elicited by general pharmacological activation of the hippocampus. We found that administration of kainic acid (KA) at a low dose (5 mg/kg) to wildtype C57BL/6 mice activated a similarly sparse number of cells in the GCL as physiologic DG stimulation by exposure to a novel, enriched environment. However, unlike physiologic stimulation, 5 mg/kg KA activated primarily old granule cells as well as GABAergic interneurons. This finding indicates that intrinsic circuit properties of the DG alone may not be sufficient to support the engagement of young granule cells, and suggest that other factors such as the specificity of the pattern of inputs, may be involved.
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Affiliation(s)
- Jason C. You
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- Memory & Brain Research Center, Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Kavitha Muralidharan
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- Memory & Brain Research Center, Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Chia-Hsuan Fu
- Memory & Brain Research Center, Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Jin Park
- Memory & Brain Research Center, Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Umberto Tosi
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Xiaohong Zhang
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Jeannie Chin
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- Memory & Brain Research Center, Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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Koh MT, Shao Y, Rosenzweig-Lipson S, Gallagher M. Treatment with levetiracetam improves cognition in a ketamine rat model of schizophrenia. Schizophr Res 2018; 193. [PMID: 28634087 PMCID: PMC5733713 DOI: 10.1016/j.schres.2017.06.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Imbalance in neural excitation and inhibition is associated with behavioral dysfunction in individuals with schizophrenia and at risk for this illness. We examined whether targeting increased neural activity with the antiepileptic agent, levetiracetam, would benefit memory performance in a preclinical model of schizophrenia that has been shown to exhibit hyperactivity in the hippocampus. Adult rats exposed to ketamine subchronically during late adolescence showed impaired hippocampal-dependent memory performance. Treatment with levetiracetam dose-dependently improved memory performance of the ketamine-exposed rats. In contrast, the antipsychotic medication risperidone was not effective in this assessment. Levetiracetam remained effective when administered concurrently with risperidone, supporting potential viability of adjunctive therapy with levetiracetam to treat cognitive deficits in schizophrenia patients under concurrent antipsychotic therapy. In addition to its pro-cognitive effect, levetiracetam was also effective in attenuating amphetamine-induced augmentation of locomotor activity, compatible with the need for therapeutic treatment of positive symptoms in schizophrenia.
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Affiliation(s)
- Ming Teng Koh
- Department of Psychological and Brain Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
| | - Yi Shao
- Department of Psychological and Brain Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 USA
| | | | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 USA,AgeneBio, Inc, 1101 E. 33rd Street, Suite C310, Baltimore, MD 21218, USA
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Leal SL, Yassa MA. Integrating new findings and examining clinical applications of pattern separation. Nat Neurosci 2018; 21:163-173. [PMID: 29371654 PMCID: PMC5898810 DOI: 10.1038/s41593-017-0065-1] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 10/28/2017] [Indexed: 11/09/2022]
Abstract
Pattern separation, the ability to independently represent and store similar experiences, is a crucial facet of episodic memory. Growing evidence suggests that the hippocampus possesses unique circuitry that is computationally capable of resolving mnemonic interference by using pattern separation. In this Review, we discuss recent advances in the understanding of this process and evaluate the caveats and limitations of linking across animal and human studies. We summarize clinical and translational studies using methods that are sensitive to pattern separation impairments, an approach that stems from the fact that the hippocampus is a major site of disruption in many brain disorders. We critically evaluate the assumptions that guide fundamental and translational studies in this area. Finally, we suggest guidelines for future research and offer ways to overcome potential interpretational challenges to increase the utility of pattern separation as a construct that can further understanding of both memory processes and brain disease.
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Affiliation(s)
- Stephanie L Leal
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Michael A Yassa
- Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA, USA.
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Koh MT, Shao Y, Sherwood A, Smith DR. Impaired hippocampal-dependent memory and reduced parvalbumin-positive interneurons in a ketamine mouse model of schizophrenia. Schizophr Res 2016; 171:187-94. [PMID: 26811256 PMCID: PMC4762714 DOI: 10.1016/j.schres.2016.01.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 01/09/2016] [Accepted: 01/11/2016] [Indexed: 01/23/2023]
Abstract
The hippocampus of patients with schizophrenia displays aberrant excess neuronal activity which affects cognitive function. Animal models of the illness have recapitulated the overactivity in the hippocampus, with a corresponding regionally localized reduction of inhibitory interneurons, consistent with that observed in patients. To better understand whether cognitive function is similarly affected in these models of hippocampal overactivity, we tested a ketamine mouse model of schizophrenia for cognitive performance in hippocampal- and medial prefrontal cortex (mPFC)-dependent tasks. We found that adult mice exposed to ketamine during adolescence were impaired on a trace fear conditioning protocol that relies on the integrity of the hippocampus. Conversely, the performance of the mice was normal on a delayed response task that is sensitive to mPFC damage. We confirmed that ketamine-exposed mice had reduced parvalbumin-positive interneurons in the hippocampus, specifically in the CA1, but not in the mPFC in keeping with the behavioral findings. These results strengthened the utility of the ketamine model for preclinical investigations of hippocampal overactivity in schizophrenia.
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Affiliation(s)
- Ming Teng Koh
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA.
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Tregellas JR, Smucny J, Legget KT, Stevens KE. Effects of a ketogenic diet on auditory gating in DBA/2 mice: A proof-of-concept study. Schizophr Res 2015; 169:351-354. [PMID: 26453015 PMCID: PMC4827327 DOI: 10.1016/j.schres.2015.09.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 09/18/2015] [Accepted: 09/21/2015] [Indexed: 11/20/2022]
Abstract
Although the ketogenic diet has shown promise in a pilot study and case report in schizophrenia, its effects in animal models of hypothesized disease mechanisms are unknown. This study examined effects of treatment with the ketogenic diet on hippocampal P20/N40 gating in DBA/2 mice, a translational endophenotype that mirrors inhibitory deficits in P50 sensory gating in schizophrenia patients. As expected, the diet increased blood ketone levels. Animals with the highest ketone levels showed the lowest P20/N40 gating ratios. These preliminary results suggest that the ketogenic diet may effectively target sensory gating deficits and is a promising area for additional research in schizophrenia.
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Affiliation(s)
- Jason R Tregellas
- Research Service, Denver VA Medical Center, Denver, CO, USA; Neuroscience Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Department of Psychiatry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
| | - Jason Smucny
- Neuroscience Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Department of Psychiatry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Kristina T Legget
- Neuroscience Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Department of Psychiatry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Karen E Stevens
- Department of Psychiatry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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