1
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Davies JR, Clayton NS. Is episodic-like memory like episodic memory? Philos Trans R Soc Lond B Biol Sci 2024; 379:20230397. [PMID: 39278246 PMCID: PMC11449162 DOI: 10.1098/rstb.2023.0397] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 03/15/2024] [Accepted: 03/22/2024] [Indexed: 09/18/2024] Open
Abstract
Episodic memory involves the conscious recollection of personally experienced events and when absent, results in profound losses to the typical human conscious experience. Over the last 2.5 decades, the debate surrounding whether episodic memory is unique to humans has seen a lot of controversy and accordingly has received significant research attention. Various behavioural paradigms have been developed to test episodic-like memory; a term designed to reflect the behavioural characteristics of episodic memory in the absence of evidence for consciously experienced recall. In this review, we first outline the most influential paradigms that have been developed to assess episodic-like memory across a variety of non-human taxa (including mammals, birds and cephalopods), namely the what-where-when memory, incidental encoding and unexpected question, and source memory paradigms. Then, we examine whether various key features of human episodic memory are conceptually represented in episodic-like memory across phylogenetically and neurologically diverse taxa, identifying similarities, differences and gaps in the literature. We conclude that the evidence is mixed, and as episodic memory encompasses a variety of cognitive structures and processes, research on episodic-like memory in non-humans should follow this multifaceted approach and assess evidence across various behavioural paradigms that each target different aspects of human episodic memory.This article is part of the theme issue 'Elements of episodic memory: lessons from 40 years of research'.
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Affiliation(s)
- James R Davies
- Department of Psychology, University of Cambridge, Cambridge CB2 3EB, UK
| | - Nicola S Clayton
- Department of Psychology, University of Cambridge, Cambridge CB2 3EB, UK
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2
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Boyle A, Brown SAB. Why might animals remember? A functional framework for episodic memory research in comparative psychology. Learn Behav 2024:10.3758/s13420-024-00645-0. [PMID: 39289293 DOI: 10.3758/s13420-024-00645-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2024] [Indexed: 09/19/2024]
Abstract
One of Clayton's major contributions to our understanding of animal minds has been her work on episodic-like memory. A central reason for the success of this work was its focus on ecological validity: rather than looking for episodic memory for arbitrary stimuli in artificial contexts, focussing on contexts in which episodic memory would serve a biological function such as food caching. This review aims to deepen this insight by surveying the numerous functions that have been proposed for episodic memory, articulating a philosophically grounded framework for understanding what exactly functions are, and drawing on these to make suggestions for future directions in the comparative cognitive psychology of episodic memory. Our review suggests four key insights. First, episodic memory may have more than one function and may have different functions in different species. Second, cross-disciplinary work is key to developing a functional account of episodic memory. Third, there is scope for further theoretical elaboration of proposals relating episodic memory to food caching and, in particular, future-oriented cognition. Finally, learning-related functions suggested by AI (artificial intelligence)-based models are a fruitful avenue for future behavioural research.
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Affiliation(s)
- Alexandria Boyle
- London School of Economics and Political Science, London, UK.
- CIFAR Azrieli Global Scholars Program, London, UK.
| | - Simon A B Brown
- London School of Economics and Political Science, London, UK
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3
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Liu K, Sibille J, Dragoi G. Nested compressed co-representations of multiple sequential experiences during sleep. Nat Neurosci 2024; 27:1816-1828. [PMID: 39030341 DOI: 10.1038/s41593-024-01703-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 06/14/2024] [Indexed: 07/21/2024]
Abstract
Animals encounter and remember multiple experiences daily. During sleep, hippocampal neuronal ensembles replay past experiences and preplay future ones. Although most previous studies investigated p/replay of a single experience, it remains unclear how the hippocampus represents many experiences without major interference during sleep. By monitoring hippocampal neuronal ensembles as rats encountered 15 distinct linear track experiences, we uncovered principles for efficient multi-experience compressed p/replay representation. First, we found a serial position effect whereby the earliest and the most recent experiences had the strongest representations. Second, distinct experiences were co-represented in a multiplexed, flickering manner during nested p/replay events, which greatly enhanced the network's representational capacity. Third, spatially contiguous and disjunct track pairs were bound together into contiguous conjunctive representations during sleep. Finally, sequences spanning day-long multi-track experiences were p/replayed at hyper-compressed ratios during sleep. These coding schemes efficiently parallelize, bind and compress multiple sequential representations with reduced interference and enhanced capacity during sleep.
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Affiliation(s)
- Kefei Liu
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, USA
- Bioscience and Biomedical Engineering Thrust, Systems Hub, Hong Kong University of Science and Technology (Guangzhou), Guangzhou, China
| | - Jeremie Sibille
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, USA
| | - George Dragoi
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, USA.
- Department of Neuroscience, Yale School of Medicine, New Haven, CT, USA.
- Wu Tsai Institute, Yale University, New Haven, CT, USA.
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4
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Attaallah B, Petitet P, Zambellas R, Toniolo S, Maio MR, Ganse-Dumrath A, Irani SR, Manohar SG, Husain M. The role of the human hippocampus in decision-making under uncertainty. Nat Hum Behav 2024; 8:1366-1382. [PMID: 38684870 PMCID: PMC11272595 DOI: 10.1038/s41562-024-01855-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 02/29/2024] [Indexed: 05/02/2024]
Abstract
The role of the hippocampus in decision-making is beginning to be more understood. Because of its prospective and inferential functions, we hypothesized that it might be required specifically when decisions involve the evaluation of uncertain values. A group of individuals with autoimmune limbic encephalitis-a condition known to focally affect the hippocampus-were tested on how they evaluate reward against uncertainty compared to reward against another key attribute: physical effort. Across four experiments requiring participants to make trade-offs between reward, uncertainty and effort, patients with acute limbic encephalitis demonstrated blunted sensitivity to reward and effort whenever uncertainty was considered, despite demonstrating intact uncertainty sensitivity. By contrast, the valuation of these two attributes (reward and effort) was intact on uncertainty-free tasks. Reduced sensitivity to changes in reward under uncertainty correlated with the severity of hippocampal damage. Together, these findings provide evidence for a context-sensitive role of the hippocampus in value-based decision-making, apparent specifically under conditions of uncertainty.
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Affiliation(s)
- Bahaaeddin Attaallah
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Pierre Petitet
- Department of Experimental Psychology, University of Oxford, Oxford, UK
| | - Rhea Zambellas
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Sofia Toniolo
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Maria Raquel Maio
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Akke Ganse-Dumrath
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- Department of Experimental Psychology, University of Oxford, Oxford, UK
| | - Sarosh R Irani
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Sanjay G Manohar
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- Department of Experimental Psychology, University of Oxford, Oxford, UK
| | - Masud Husain
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- Department of Experimental Psychology, University of Oxford, Oxford, UK
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5
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Tononi G, Boly M, Cirelli C. Consciousness and sleep. Neuron 2024; 112:1568-1594. [PMID: 38697113 PMCID: PMC11105109 DOI: 10.1016/j.neuron.2024.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/04/2024] [Accepted: 04/10/2024] [Indexed: 05/04/2024]
Abstract
Sleep is a universal, essential biological process. It is also an invaluable window on consciousness. It tells us that consciousness can be lost but also that it can be regained, in all its richness, when we are disconnected from the environment and unable to reflect. By considering the neurophysiological differences between dreaming and dreamless sleep, we can learn about the substrate of consciousness and understand why it vanishes. We also learn that the ongoing state of the substrate of consciousness determines the way each experience feels regardless of how it is triggered-endogenously or exogenously. Dreaming consciousness is also a window on sleep and its functions. Dreams tell us that the sleeping brain is remarkably lively, recombining intrinsic activation patterns from a vast repertoire, freed from the requirements of ongoing behavior and cognitive control.
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Affiliation(s)
- Giulio Tononi
- Department of Psychiatry, University of Wisconsin, Madison, WI 53719, USA.
| | - Melanie Boly
- Department of Neurology, University of Wisconsin, Madison, WI 53719, USA
| | - Chiara Cirelli
- Department of Psychiatry, University of Wisconsin, Madison, WI 53719, USA
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6
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Miller TD, Kennard C, Gowland PA, Antoniades CA, Rosenthal CR. Differential effects of bilateral hippocampal CA3 damage on the implicit learning and recognition of complex event sequences. Cogn Neurosci 2024; 15:27-55. [PMID: 38384107 PMCID: PMC11147457 DOI: 10.1080/17588928.2024.2315818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 01/25/2024] [Indexed: 02/23/2024]
Abstract
Learning regularities in the environment is a fundament of human cognition, which is supported by a network of brain regions that include the hippocampus. In two experiments, we assessed the effects of selective bilateral damage to human hippocampal subregion CA3, which was associated with autobiographical episodic amnesia extending ~50 years prior to the damage, on the ability to recognize complex, deterministic event sequences presented either in a spatial or a non-spatial configuration. In contrast to findings from related paradigms, modalities, and homologue species, hippocampal damage did not preclude recognition memory for an event sequence studied and tested at four spatial locations, whereas recognition memory for an event sequence presented at a single location was at chance. In two additional experiments, recognition memory for novel single-items was intact, whereas the ability to recognize novel single-items in a different location from that presented at study was at chance. The results are at variance with a general role of the hippocampus in the learning and recognition of complex event sequences based on non-adjacent spatial and temporal dependencies. We discuss the impact of the results on established theoretical accounts of the hippocampal contributions to implicit sequence learning and episodic memory.
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Affiliation(s)
- Thomas D. Miller
- Wellcome Centre for Human Neuroimaging, University College London, London, UK
- National Hospital for Neurology and Neurosurgery, Queen Square, London, UK
| | - Christopher Kennard
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Penny A. Gowland
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | | | - Clive R. Rosenthal
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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7
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Spens E, Burgess N. A generative model of memory construction and consolidation. Nat Hum Behav 2024; 8:526-543. [PMID: 38242925 PMCID: PMC10963272 DOI: 10.1038/s41562-023-01799-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 12/05/2023] [Indexed: 01/21/2024]
Abstract
Episodic memories are (re)constructed, share neural substrates with imagination, combine unique features with schema-based predictions and show schema-based distortions that increase with consolidation. Here we present a computational model in which hippocampal replay (from an autoassociative network) trains generative models (variational autoencoders) to (re)create sensory experiences from latent variable representations in entorhinal, medial prefrontal and anterolateral temporal cortices via the hippocampal formation. Simulations show effects of memory age and hippocampal lesions in agreement with previous models, but also provide mechanisms for semantic memory, imagination, episodic future thinking, relational inference and schema-based distortions including boundary extension. The model explains how unique sensory and predictable conceptual elements of memories are stored and reconstructed by efficiently combining both hippocampal and neocortical systems, optimizing the use of limited hippocampal storage for new and unusual information. Overall, we believe hippocampal replay training generative models provides a comprehensive account of memory construction, imagination and consolidation.
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Affiliation(s)
- Eleanor Spens
- UCL Institute of Cognitive Neuroscience, University College London, London, UK.
| | - Neil Burgess
- UCL Institute of Cognitive Neuroscience, University College London, London, UK.
- UCL Queen Square Institute of Neurology, University College London, London, UK.
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8
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Campo Redondo M, Andrade G. Nightmare experiences and perceived ethnic discrimination amongst female university students in the United Arab Emirates: a cross-sectional study. J Sleep Res 2024:e14148. [PMID: 38233953 DOI: 10.1111/jsr.14148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Revised: 12/28/2023] [Accepted: 01/02/2024] [Indexed: 01/19/2024]
Abstract
Perceived ethnic discrimination is known to be associated with anxiety and depression, and in turn, anxiety and depression are known to be associated with nightmare frequency and distress. This elicits a question: is perceived ethnic discrimination associated with nightmare frequency and distress? In this study, 179 female university students from the United Arab Emirates were assessed to answer that question. Results showed that while anxiety and depression were related to nightmare experiences, perceived ethnic discrimination was a stronger predictor of nightmare experiences. We posit two explanations for this finding: one based on psychoanalytical insights, and the other based on the Disposition-Stress model with neurobiological correlates. No significant differences were found across ethnicity when it comes to nightmare experiences or perceived ethnic discrimination. This is an encouraging sign of optimal societal integration in the United Arab Emirates.
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9
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Dragoi G. The generative grammar of the brain: a critique of internally generated representations. Nat Rev Neurosci 2024; 25:60-75. [PMID: 38036709 DOI: 10.1038/s41583-023-00763-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2023] [Indexed: 12/02/2023]
Abstract
The past decade of progress in neurobiology has uncovered important organizational principles for network preconfiguration and neuronal selection that suggest a generative grammar exists in the brain. In this Perspective, I discuss the competence of the hippocampal neural network to generically express temporally compressed sequences of neuronal firing that represent novel experiences, which is envisioned as a form of generative neural syntax supporting a neurobiological perspective on brain function. I compare this neural competence with the hippocampal network performance that represents specific experiences with higher fidelity after new learning during replay, which is envisioned as a form of neural semantic that supports a complementary neuropsychological perspective. I also demonstrate how the syntax of network competence emerges a priori during early postnatal life and is followed by the later development of network performance that enables rapid encoding and memory consolidation. Thus, I propose that this generative grammar of the brain is essential for internally generated representations, which are crucial for the cognitive processes underlying learning and memory, prospection, and inference, which ultimately underlie our reason and representation of the world.
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Affiliation(s)
- George Dragoi
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA.
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA.
- Wu Tsai Institute, Yale University, New Haven, CT, USA.
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10
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Unlu MD, Asci H, Yusuf Tepebasi M, Arlioglu M, Huseynov I, Ozmen O, Sezer S, Demirci S. The ameliorative effects of cannabidiol on methotrexate-induced neuroinflammation and neuronal apoptosis via inhibiting endoplasmic reticulum and mitochondrial stress. J Biochem Mol Toxicol 2024; 38:e23571. [PMID: 37927177 DOI: 10.1002/jbt.23571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 08/16/2023] [Accepted: 10/18/2023] [Indexed: 11/07/2023]
Abstract
Methotrexate (MTX) is an antineoplastic agent and has neurotoxic effects. It exerts its toxic effect on the brain by triggering inflammation and apoptosis. Cannabidiol (CBD) is an agent known for its antioxidant, anti-inflammatory effects in various tissues. The aim of this study is to examine the protective effects of CBD treatment in various brain structures from MTX damage and to evaluate the effect of intracellular pathways involved in apoptosis. Thirty-two adult Wistar Albino female rats were divided into four groups as control, MTX (20 mg/kg intraperitoneally [i.p.]), MTX + CBD (0.1 mL of 5 mg/kg i.p.), and CBD (for 7 days, i.p.). At the end of the experiment, brain tissues collected for biochemical analyses as total oxidant status (TOS), total antioxidant status, oxidative stress index (OSI), histopathological and immunohistochemical analyses as tumor necrosis factor-α (TNF-α), serotonin, mammalian target of rapamycin (mTOR) staining, genetic analyses as caspase-9 (Cas-9), caspase-12 (Cas-12), C/EBP homologous protein (CHOP), and cytochrome-c (Cyt-c) gene expressions. In the histopathological and immunohistochemical evaluation, hyperemia, microhemorrhage, neuronal loss, and significant decreasing expressions of seratonin were observed in the cortex, hippocampus, and cerebellum regions in the MTX group. mTOR, TNF-α, Cas-9, Cas-12, CHOP, and Cyt-c expressions with TOS and OSI levels were increased in the cortex. It was observed that these findings were reversed after CBD application in all regions. MTX triggers neuronal apoptosis via endoplasmic reticulum and mitochondrial stress while destroying serotonergic neurons. The reversal of the pathological changes with CBD treatment proves that it has anti-inflammatory and antiapoptotic activity in brain.
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Affiliation(s)
- Melike D Unlu
- Department of Neurology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Halil Asci
- Department of Pharmacology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - M Yusuf Tepebasi
- Department of Genetic, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Melih Arlioglu
- Department of Pharmacology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Ibrahim Huseynov
- Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| | - Ozlem Ozmen
- Department of Pathology, Faculty of Veterinary, Burdur Mehmet Akif Ersoy University, Burdur, Turkey
| | - Serdar Sezer
- Department of Pharmacology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
- Department of Pharmacology, Natural Products Application and Research Center (SUDUM), Suleyman Demirel University, Isparta, Turkey
| | - Serpil Demirci
- Department of Neurology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
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11
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Picard-Deland C, Bernardi G, Genzel L, Dresler M, Schoch SF. Memory reactivations during sleep: a neural basis of dream experiences? Trends Cogn Sci 2023; 27:568-582. [PMID: 36959079 DOI: 10.1016/j.tics.2023.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 02/18/2023] [Accepted: 02/28/2023] [Indexed: 03/25/2023]
Abstract
Newly encoded memory traces are spontaneously reactivated during sleep. Since their discovery in the 1990s, these memory reactivations have been discussed as a potential neural basis for dream experiences. New results from animal and human research, as well as from the rapidly growing field of sleep and dream engineering, provide essential insights into this question, and reveal both strong parallels and disparities between the two phenomena. We suggest that, although memory reactivations may contribute to subjective experiences across different states of consciousness, they are not likely to be the primary neural basis of dreaming. We identify important limitations in current research paradigms and suggest novel strategies to address this question empirically.
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Affiliation(s)
- Claudia Picard-Deland
- Dream and Nightmare Laboratory, Center for Advanced Research in Sleep Medicine, University of Montreal, Montreal, QC, Canada
| | - Giulio Bernardi
- Institutions, Markets, Technologies (IMT) School for Advanced Studies Lucca, Lucca, Italy
| | - Lisa Genzel
- Donders Institute for Brain, Cognition, and Behaviour, Radboud University, Nijmegen, The Netherlands
| | - Martin Dresler
- Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Sarah F Schoch
- Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands; Center of Competence Sleep and Health Zurich, University of Zurich, Zurich, Switzerland.
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12
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Bergouignan L, Paz-Alonso PM. Simulating the situated-self drives hippocampo-cortical engagement during inner narration of events. Cereb Cortex 2022; 32:5716-5731. [PMID: 35275987 DOI: 10.1093/cercor/bhac047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 01/25/2023] Open
Abstract
We often use inner narration when thinking about past and future events. The present paradigm explicitly addresses the influence of the language used in inner narration on the hippocampus-dependent event construction process. We assessed the language context effect during the inner narration of different event types: past, future, daydream, and self-unrelated fictitious events. The language context was assessed via a fluent bilingual population who used inner narration, either in their first language (L1) or second language (L2). Not all inner narration of events elicited hippocampo-cortical activity. In fact, only the angular gyrus and precuneus-retrosplenial cortex were activated by inner narration across all event types. More precisely, only inner narration of events which entailed the simulation of bodily self-location in space (whether or not they were time-marked: past, future, daydream) depended on the hippocampo-cortical system, while inner narration of events that did not entail bodily self-location (self-unrelated fictitious) did not. The language context of the narration influenced the bilinguals' hippocampo-cortical system by enhancing the co-activation of semantic areas with the hippocampus for inner narration of events in the L2. Overall, this study highlights 2 important characteristics of hippocampo-cortical-dependent inner narration of events: The core episodic hippocampal system is activated for inner narration of events simulating self-location in space (regardless of time-marking), and the inner language used for narration (L1 or L2) mediates hippocampal functional connectivity.
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Affiliation(s)
- Loretxu Bergouignan
- BCBL - Basque Center on Cognition, Brain and Language, Mikeletegi Pasealekua 69, 20009 Donostia, Gipuzkoa, Spain
| | - Pedro M Paz-Alonso
- BCBL - Basque Center on Cognition, Brain and Language, Mikeletegi Pasealekua 69, 20009 Donostia, Gipuzkoa, Spain.,IKERBASQUE - Basque Foundation for Science, 48013 Bilbo, Bizkaia, Spain
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13
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Murillo-Rodríguez E, Coronado-Álvarez A, López-Muciño LA, Pastrana-Trejo JC, Viana-Torre G, Barberena JJ, Soriano-Nava DM, García-García F. Neurobiology of dream activity and effects of stimulants on dreams. Curr Top Med Chem 2022; 22:1280-1295. [PMID: 35761491 DOI: 10.2174/1568026622666220627162032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Revised: 03/18/2022] [Accepted: 04/11/2022] [Indexed: 11/22/2022]
Abstract
The sleep-wake cycle is the result of the activity of a multiple neurobiological network interaction. Dreaming feature is one interesting sleep phenomena that represents sensorial components, mostly visual perceptions, accompanied with intense emotions. Further complexity has been added to the topic of the neurobiological mechanism of dreams generation by the current data that suggests the influence of drugs on dream generation. Here, we discuss the review on some of the neurobiological mechanism of the regulation of dream activity, with special emphasis on the effects of stimulants on dreaming.
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Affiliation(s)
- Eric Murillo-Rodríguez
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México.,Intercontinental Neuroscience Research Group
| | - Astrid Coronado-Álvarez
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México.,Intercontinental Neuroscience Research Group
| | - Luis Angel López-Muciño
- Health Sciences Program. Health Sciences Institute. Veracruzana University. Xalapa. Veracruz. Mexico
| | - José Carlos Pastrana-Trejo
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México.,Intercontinental Neuroscience Research Group
| | - Gerardo Viana-Torre
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México.,Intercontinental Neuroscience Research Group
| | - Juan José Barberena
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México.,Intercontinental Neuroscience Research Group.,Escuela de Psicología, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México
| | - Daniela Marcia Soriano-Nava
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud. Universidad Anáhuac Mayab. Mérida, Yucatán. México.,Intercontinental Neuroscience Research Group
| | - Fabio García-García
- Intercontinental Neuroscience Research Group.,Health Sciences Program. Health Sciences Institute. Veracruzana University. Xalapa. Veracruz. Mexico
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14
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Deperrois N, Petrovici MA, Senn W, Jordan J. Learning cortical representations through perturbed and adversarial dreaming. eLife 2022; 11:76384. [PMID: 35384841 PMCID: PMC9071267 DOI: 10.7554/elife.76384] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 03/07/2022] [Indexed: 11/24/2022] Open
Abstract
Humans and other animals learn to extract general concepts from sensory experience without extensive teaching. This ability is thought to be facilitated by offline states like sleep where previous experiences are systemically replayed. However, the characteristic creative nature of dreams suggests that learning semantic representations may go beyond merely replaying previous experiences. We support this hypothesis by implementing a cortical architecture inspired by generative adversarial networks (GANs). Learning in our model is organized across three different global brain states mimicking wakefulness, non-rapid eye movement (NREM), and REM sleep, optimizing different, but complementary, objective functions. We train the model on standard datasets of natural images and evaluate the quality of the learned representations. Our results suggest that generating new, virtual sensory inputs via adversarial dreaming during REM sleep is essential for extracting semantic concepts, while replaying episodic memories via perturbed dreaming during NREM sleep improves the robustness of latent representations. The model provides a new computational perspective on sleep states, memory replay, and dreams, and suggests a cortical implementation of GANs.
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Affiliation(s)
| | | | - Walter Senn
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Jakob Jordan
- Department of Physiology, University of Bern, Bern, Switzerland
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15
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Circadian and Sleep Modulation of Dreaming in Women with Major Depression. Clocks Sleep 2022; 4:114-128. [PMID: 35323166 PMCID: PMC8947272 DOI: 10.3390/clockssleep4010012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/16/2022] Open
Abstract
Growing evidence indicates an association between reduced dream recall and depressive symptomatology. Here, we tested the prediction that reduced dream recall in individuals experiencing major depressive disorder (MDD) is due to alterations in circadian and sleep processes. Nine young healthy women (20−31 years) and eight young unmedicated women (20−31 years) diagnosed with MDD underwent a 40 h multiple nap protocol with ten alternating cycles of 150 min wake/75 min sleep under a stringently controlled circadian laboratory protocol. After each nap, we assessed dream recall, number of dreams and dream emotional load using the Sleep Mentation Questionnaire. Dream recall and the number of dreams did not significantly differ between groups (pFDR > 0.1). However, there was a significant difference for the dream emotional load (interaction of “Group” vs. “Time”, pFDR = 0.01). Women with MDD had a two-fold higher (negative) emotional load as compared to healthy control women, particularly after naps during the circadian night (between ~22:00 h and ~05:00 h; Tukey−Kramer test, p = 0.009). Furthermore, higher (negative) dream emotional load was associated with impaired mood levels in both groups (R2 = 0.71; p < 0.001). Our findings suggest that the circadian and sleep modulation of dreaming may remain intact in unmedicated young women experiencing MDD.
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Triantafyllou AS, Ilias I, Economou NT, Pappa A, Koukkou E, Steiropoulos P. Dream Recall/Affect and Cortisol: An Exploratory Study. Clocks Sleep 2022; 4:9-15. [PMID: 35225949 PMCID: PMC8883916 DOI: 10.3390/clockssleep4010003] [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: 12/31/2021] [Revised: 01/19/2022] [Accepted: 01/26/2022] [Indexed: 11/16/2022] Open
Abstract
The effect of cortisol on dreams has been scarcely studied. The aim of this exploratory study was to assess the possible effect of cortisol levels on dream recall/affect, considering, in female subjects, their menstrual cycle phase. Fifteen men and fifteen women were recruited. Saliva samples were used for the detection of cortisol levels. Participants were instructed to provide four saliva samples, during three consecutive days. After awakening, on the second and third day, they were asked whether they could recall the previous night’s dreams and whether these were pleasant or unpleasant. Female subjects followed this procedure twice: firstly, during the luteal phase and, secondly, during the follicular phase of the menstrual cycle. Subjects with higher evening or higher morning cortisol levels tended to show increased dream recall; a non-statistically significant association between morning cortisol levels and positive dream affect was also found. This association acquired statistical significance for salivary morning cortisol levels exceeding the upper normal level of 19.1 nmol/L (OR: 4.444, 95% CI: 1.108–17.830, p-value: 0.039). No connection between menstrual cycle stages and dream recall/affect was detected. In conclusion, cortisol may be a crucial neuromodulator, affecting dream recall and content. Therefore, its effects on sleep and dreams should be further studied.
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Affiliation(s)
- Alexandros S. Triantafyllou
- MSc Program in Sleep Medicine, Medical School, Democritus University of Thrace, 68100 Alexandroupolis, Greece; (A.S.T.); (N.-T.E.); (P.S.)
| | - Ioannis Ilias
- Department of Endocrinology, Diabetes and Metabolism, Elena Venizelou Hospital, 11521 Athens, Greece; (A.P.); (E.K.)
- Correspondence: ; Tel.: +30-213-205-1389
| | - Nicholas-Tiberio Economou
- MSc Program in Sleep Medicine, Medical School, Democritus University of Thrace, 68100 Alexandroupolis, Greece; (A.S.T.); (N.-T.E.); (P.S.)
- Sleep Study Unit, Eginition Hospital, University of Athens & Enypnion Sleep Disorders—Epilepsy Center, 11521 Athens, Greece
| | - Athina Pappa
- Department of Endocrinology, Diabetes and Metabolism, Elena Venizelou Hospital, 11521 Athens, Greece; (A.P.); (E.K.)
| | - Eftychia Koukkou
- Department of Endocrinology, Diabetes and Metabolism, Elena Venizelou Hospital, 11521 Athens, Greece; (A.P.); (E.K.)
| | - Paschalis Steiropoulos
- MSc Program in Sleep Medicine, Medical School, Democritus University of Thrace, 68100 Alexandroupolis, Greece; (A.S.T.); (N.-T.E.); (P.S.)
- Department of Pneumonology, Medical School, Democritus University of Thrace, 68100 Alexandroupolis, Greece
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17
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O’Mara S. Biopsychosocial Functions of Human Walking and Adherence to Behaviourally Demanding Belief Systems: A Narrative Review. Front Psychol 2021; 12:654122. [PMID: 34421710 PMCID: PMC8371042 DOI: 10.3389/fpsyg.2021.654122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 07/02/2021] [Indexed: 01/05/2023] Open
Abstract
Human walking is a socially embedded and shaped biological adaptation: it frees our hands, makes our minds mobile, and is deeply health promoting. Yet, today, physical inactivity is an unsolved, major public health problem. However, globally, tens of millions of people annually undertake ancient, significant and enduring traditions of physiologically and psychologically arduous walks (pilgrimages) of days-to-weeks extent. Pilgrim walking is a significant human activity requiring weighty commitments of time, action and belief, as well as community support. Paradoxically, human walking is most studied on treadmills, not 'in the wild', while mechanistically vital, treadmill studies of walking cannot, in principle, address why humans walk extraordinary distances together to demonstrate their adherence to a behaviourally demanding belief system. Pilgrim walkers provide a rich 'living laboratory' bridging humanistic inquiries, to progressive theoretical and empirical investigations of human walking arising from a behaviourally demanding belief system. Pilgrims vary demographically and undertake arduous journeys on precisely mapped routes of tracked, titrated doses and durations on terrain of varying difficulty, allowing investigations from molecular to cultural levels of analysis. Using the reciprocal perspectives of 'inside→out' (where processes within brain and body initiate, support and entrain movement) and 'outside→in' (where processes in the world beyond brain and body drive activity within brain and body), we examine how pilgrim walking might shape personal, social and transcendental processes, revealing potential mechanisms supporting the body and brain in motion, to how pilgrim walking might offer policy solutions for physical inactivity.
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Affiliation(s)
- Shane O’Mara
- School of Psychology and Institute of Neuroscience, Trinity College Dublin, University of Dublin, Dublin, Ireland
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18
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Dream Recall/Affect and the Hypothalamic-Pituitary-Adrenal Axis. Clocks Sleep 2021; 3:403-408. [PMID: 34449575 PMCID: PMC8395463 DOI: 10.3390/clockssleep3030027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 07/08/2021] [Accepted: 07/16/2021] [Indexed: 12/02/2022] Open
Abstract
In this concise review, we present an overview of research on dream recall/affect and of the hypothalamic–pituitary–adrenal (HPA) axis, discussing caveats regarding the action of hormones of the HPA axis (mainly cortisol and its free form, cortisol-binding globulin and glucocorticoid receptors). We present results of studies regarding dream recall/affect and the HPA axis under physiological (such as waking) or pathological conditions (such as in Cushing’s syndrome or stressful situations). Finally, we try to integrate the effect of the current COVID-19 situation with dream recall/affect vis-à-vis the HPA axis.
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Scarpelli S, Alfonsi V, Gorgoni M, Giannini AM, De Gennaro L. Investigation on Neurobiological Mechanisms of Dreaming in the New Decade. Brain Sci 2021; 11:brainsci11020220. [PMID: 33670180 PMCID: PMC7916906 DOI: 10.3390/brainsci11020220] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/06/2021] [Accepted: 02/08/2021] [Indexed: 02/05/2023] Open
Abstract
Dream research has advanced significantly over the last twenty years, thanks to the new applications of neuroimaging and electrophysiological techniques. Many findings pointed out that mental activity during sleep and wakefulness shared similar neural bases. On the other side, recent studies have highlighted that dream experience is promoted by significant brain activation, characterized by reduced low frequencies and increased rapid frequencies. Additionally, several studies confirmed that the posterior parietal area and prefrontal cortex are responsible for dream experience. Further, early results revealed that dreaming might be manipulated by sensory stimulations that would provoke the incorporation of specific cues into the dream scenario. Recently, transcranial stimulation techniques have been applied to modulate the level of consciousness during sleep, supporting previous findings and adding new information about neural correlates of dream recall. Overall, although multiple studies suggest that both the continuity and activation hypotheses provide a growing understanding of neural processes underlying dreaming, several issues are still unsolved. The impact of state-/trait-like variables, the influence of circadian and homeostatic factors, and the examination of parasomnia-like events to access dream contents are all opened issues deserving further deepening in future research.
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Affiliation(s)
- Serena Scarpelli
- Body and Action Lab, IRCCS Fondazione Santa Lucia, 00179 Rome, Italy; (V.A.); (L.D.G.)
- Department of Psychology, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (A.M.G.)
- Correspondence: ; Tel.: +39-06-4991-7508
| | - Valentina Alfonsi
- Body and Action Lab, IRCCS Fondazione Santa Lucia, 00179 Rome, Italy; (V.A.); (L.D.G.)
| | - Maurizio Gorgoni
- Department of Psychology, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (A.M.G.)
| | - Anna Maria Giannini
- Department of Psychology, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (A.M.G.)
| | - Luigi De Gennaro
- Body and Action Lab, IRCCS Fondazione Santa Lucia, 00179 Rome, Italy; (V.A.); (L.D.G.)
- Department of Psychology, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (A.M.G.)
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McCormick C, Dalton MA, Zeidman P, Maguire EA. Characterising the hippocampal response to perception, construction and complexity. Cortex 2021; 137:1-17. [PMID: 33571913 PMCID: PMC8048772 DOI: 10.1016/j.cortex.2020.12.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 11/25/2020] [Accepted: 12/04/2020] [Indexed: 12/31/2022]
Abstract
The precise role played by the hippocampus in supporting cognitive functions such as episodic memory and future thinking is debated, but there is general agreement that it involves constructing representations comprised of numerous elements. Visual scenes have been deployed extensively in cognitive neuroscience because they are paradigmatic multi-element stimuli. However, questions remain about the specificity and nature of the hippocampal response to scenes. Here, we devised a paradigm in which we had participants search pairs of images for either colour or layout differences, thought to be associated with perceptual or spatial constructive processes respectively. Importantly, images depicted either naturalistic scenes or phase-scrambled versions of the same scenes, and were either simple or complex. Using this paradigm during functional MRI scanning, we addressed three questions: 1. Is the hippocampus recruited specifically during scene processing? 2. If the hippocampus is more active in response to scenes, does searching for colour or layout differences influence its activation? 3. Does the complexity of the scenes affect its response? We found that, compared to phase-scrambled versions of the scenes, the hippocampus was more responsive to scene stimuli. Moreover, a clear anatomical distinction was evident, with colour detection in scenes engaging the posterior hippocampus whereas layout detection in scenes recruited the anterior hippocampus. The complexity of the scenes did not influence hippocampal activity. These findings seem to align with perspectives that propose the hippocampus is especially attuned to scenes, and its involvement occurs irrespective of the cognitive process or the complexity of the scenes.
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Affiliation(s)
- Cornelia McCormick
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, WC1N 3AR, UK
| | - Marshall A Dalton
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, WC1N 3AR, UK
| | - Peter Zeidman
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, WC1N 3AR, UK
| | - Eleanor A Maguire
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, WC1N 3AR, UK.
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22
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Abstract
Deep inside the temporal lobe of the brain, the hippocampus has a central role in our ability to remember, imagine and dream.
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Affiliation(s)
- Erin J Wamsley
- Department of Psychology and Program in Neuroscience, Furman UniversityGreenvilleUnited States
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