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Rennó-Costa C, da Silva ACC, Blanco W, Ribeiro S. Computational models of memory consolidation and long-term synaptic plasticity during sleep. Neurobiol Learn Mem 2018; 160:32-47. [PMID: 30321652 DOI: 10.1016/j.nlm.2018.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 09/18/2018] [Accepted: 10/11/2018] [Indexed: 12/19/2022]
Abstract
The brain stores memories by persistently changing the connectivity between neurons. Sleep is known to be critical for these changes to endure. Research on the neurobiology of sleep and the mechanisms of long-term synaptic plasticity has provided data in support of various theories of how brain activity during sleep affects long-term synaptic plasticity. The experimental findings - and therefore the theories - are apparently quite contradictory, with some evidence pointing to a role of sleep in the forgetting of irrelevant memories, whereas other results indicate that sleep supports the reinforcement of the most valuable recollections. A unified theoretical framework is in need. Computational modeling and simulation provide grounds for the quantitative testing and comparison of theoretical predictions and observed data, and might serve as a strategy to organize the rather complicated and diverse pool of data and methodologies used in sleep research. This review article outlines the emerging progress in the computational modeling and simulation of the main theories on the role of sleep in memory consolidation.
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Affiliation(s)
- César Rennó-Costa
- BioMe - Bioinformatics Multidisciplinary Environment, Federal University of Rio Grande do Norte, Natal, Brazil; Digital Metropolis Institute, Federal University of Rio Grande do Norte, Natal, Brazil
| | - Ana Cláudia Costa da Silva
- BioMe - Bioinformatics Multidisciplinary Environment, Federal University of Rio Grande do Norte, Natal, Brazil; Digital Metropolis Institute, Federal University of Rio Grande do Norte, Natal, Brazil; Brain Institute, Federal University of Rio Grande do Norte, Natal, Brazil; Federal University of Paraiba, João Pessoa, Brazil
| | - Wilfredo Blanco
- BioMe - Bioinformatics Multidisciplinary Environment, Federal University of Rio Grande do Norte, Natal, Brazil; Brain Institute, Federal University of Rio Grande do Norte, Natal, Brazil; State University of Rio Grande do Norte, Natal, Brazil
| | - Sidarta Ribeiro
- Brain Institute, Federal University of Rio Grande do Norte, Natal, Brazil.
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Puentes-Mestril C, Aton SJ. Linking Network Activity to Synaptic Plasticity during Sleep: Hypotheses and Recent Data. Front Neural Circuits 2017; 11:61. [PMID: 28932187 PMCID: PMC5592216 DOI: 10.3389/fncir.2017.00061] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 08/23/2017] [Indexed: 12/22/2022] Open
Abstract
Research findings over the past two decades have supported a link between sleep states and synaptic plasticity. Numerous mechanistic hypotheses have been put forth to explain this relationship. For example, multiple studies have shown structural alterations to synapses (including changes in synaptic volume, spine density, and receptor composition) indicative of synaptic weakening after a period of sleep. Direct measures of neuronal activity and synaptic strength support the idea that a period of sleep can reduce synaptic strength. This has led to the synaptic homeostasis hypothesis (SHY), which asserts that during slow wave sleep, synapses are downscaled throughout the brain to counteract net strengthening of network synapses during waking experience (e.g., during learning). However, neither the cellular mechanisms mediating these synaptic changes, nor the sleep-dependent activity changes driving those cellular events are well-defined. Here we discuss potential cellular and network dynamic mechanisms which could underlie reductions in synaptic strength during sleep. We also discuss recent findings demonstrating circuit-specific synaptic strengthening (rather than weakening) during sleep. Based on these data, we explore the hypothetical role of sleep-associated network activity patterns in driving synaptic strengthening. We propose an alternative to SHY—namely that depending on experience during prior wake, a variety of plasticity mechanisms may operate in the brain during sleep. We conclude that either synaptic strengthening or synaptic weakening can occur across sleep, depending on changes to specific neural circuits (such as gene expression and protein translation) induced by experiences in wake. Clarifying the mechanisms underlying these different forms of sleep-dependent plasticity will significantly advance our understanding of how sleep benefits various cognitive functions.
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Affiliation(s)
- Carlos Puentes-Mestril
- Neuroscience Graduate Program, Department of Molecular, Cellular, and Developmental Biology, University of MichiganAnn Arbor, MI, United States
| | - Sara J Aton
- Neuroscience Graduate Program, Department of Molecular, Cellular, and Developmental Biology, University of MichiganAnn Arbor, MI, United States
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Potential Role of Synaptic Activity to Inhibit LTD Induction in Rat Visual Cortex. Neural Plast 2017; 2016:1401935. [PMID: 28050286 PMCID: PMC5168486 DOI: 10.1155/2016/1401935] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 09/08/2016] [Accepted: 10/05/2016] [Indexed: 12/31/2022] Open
Abstract
Long-term depression (LTD), a widely studied form of activity-dependent synaptic plasticity, is typically induced by prolonged low-frequency stimulation (LFS). Interestingly, LFS is highly effective in eliciting LTD in vitro, but much less so under in vivo conditions; the reasons for the resistance of the intact brain to express LTD are not well understood. We examined if levels of background electrocorticographic (ECoG) activity influence LTD induction in the thalamocortical visual system of rats under very deep urethane anesthesia, inducing a brain state of reduced spontaneous cortical activity. Under these conditions, LFS applied to the lateral geniculate nucleus resulted in LTD of field postsynaptic potentials (fPSPs) recorded in the primary visual cortex (V1). Pairing LFS with stimulation of the brainstem (pedunculopontine) reticular formation resulted in the appearance of faster, more complex activity in V1 and prevented LTD induction, an effect that did not require muscarinic or nicotinic receptors. Reticular stimulation alone (without LFS) had no effect on cortical fPSPs. These results show that excitation of the brainstem activating system blocks the induction of LTD in V1. Thus, higher levels of neural activity may inhibit depression at cortical synapses, a hypothesis that could explain discrepancies regarding LTD induction in previous in vivo and in vitro work.
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Age-Dependent Switch of the Role of Serotonergic 5-HT1A Receptors in Gating Long-Term Potentiation in Rat Visual Cortex In Vivo. Neural Plast 2016; 2016:6404082. [PMID: 27247804 PMCID: PMC4877497 DOI: 10.1155/2016/6404082] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 04/15/2016] [Accepted: 04/17/2016] [Indexed: 11/30/2022] Open
Abstract
The rodent primary visual cortex (V1) is densely innervated by serotonergic axons and previous in vitro work has shown that serotonin (5-HT) can modulate plasticity (e.g., long-term potentiation (LTP)) at V1 synapses. However, little work has examined the effects of 5-HT on LTP under in vivo conditions. We examined the role of 5-HT on LTP in V1 elicited by theta burst stimulation (TBS) of the lateral geniculate nucleus in urethane-anesthetized (adult and juvenile) rats. Thalamic TBS consistently induced potentiation of field postsynaptic potentials (fPSPs) recorded in V1. While 5-HT application (0.1–10 mM) itself did not alter LTP levels, the broad-acting 5-HT receptor antagonists methiothepin (1 mM) resulted in a clear facilitation of LTP in adult animals, an effect that was mimicked by the selective 5-HT1A receptor antagonist WAY 100635 (1 mM). Interestingly, in juvenile rats, WAY 100635 application inhibited LTP, indicative of an age-dependent switch in the role of 5-HT1A receptors in gating V1 plasticity. Analyses of spontaneous electrocorticographic (ECoG) activity in V1 indicated that the antagonist-induced LTP enhancement was not related to systematic changes in oscillatory activity in V1. Together, these data suggest a facilitating role of 5-HT1A receptor activation on LTP in the juvenile V1, which switches to a tonic, inhibitory influence in adulthood.
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Rodríguez-Durán LF, Escobar ML. NMDA receptor activation and PKC but not PKA lead to the modification of the long-term potentiation in the insular cortex induced by conditioned taste aversion: Differential role of kinases in metaplasticity. Behav Brain Res 2014; 266:58-62. [DOI: 10.1016/j.bbr.2014.02.049] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 02/20/2014] [Accepted: 02/27/2014] [Indexed: 11/15/2022]
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Abstract
Over more than a century of research has established the fact that sleep benefits the retention of memory. In this review we aim to comprehensively cover the field of "sleep and memory" research by providing a historical perspective on concepts and a discussion of more recent key findings. Whereas initial theories posed a passive role for sleep enhancing memories by protecting them from interfering stimuli, current theories highlight an active role for sleep in which memories undergo a process of system consolidation during sleep. Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms, as well as developmental aspects in these processes. Specifically, newer findings characterize sleep as a brain state optimizing memory consolidation, in opposition to the waking brain being optimized for encoding of memories. Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. While elaborated with respect to hippocampus-dependent memories, the concept of an active redistribution of memory representations from networks serving as temporary store into long-term stores might hold also for non-hippocampus-dependent memory, and even for nonneuronal, i.e., immunological memories, giving rise to the idea that the offline consolidation of memory during sleep represents a principle of long-term memory formation established in quite different physiological systems.
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Affiliation(s)
- Björn Rasch
- Division of Biopsychology, Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland.
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Comparison of long-term potentiation (LTP) in the medial (monocular) and lateral (binocular) rat primary visual cortex. Brain Res 2012; 1488:51-9. [PMID: 23063890 DOI: 10.1016/j.brainres.2012.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 09/04/2012] [Accepted: 10/02/2012] [Indexed: 11/23/2022]
Abstract
Recent evidence suggests that the primary visual cortex (V1) of rodents expresses surprisingly high levels of plasticity into adulthood. For example, long-term potentiation (LTP) is readily induced in the mature V1 of adult rodents in vivo. Here, adult, urethane-anesthetized rats were used for a detailed characterization of LTP in the pathway between the dorsal lateral geniculate nucleus (dLGN) and ipsilateral V1. Strong theta-burst stimulation (TBS) of the LGN resulted in LTP of field postsynaptic potentials (fPSPs) recorded in the lateral (binocular) aspects of V1 (l-V1), but failed to do so in the medial (monocular) V1 (m-V1). Administration of MK 801 (1mg/kg, i.p.) blocked LTP in l-V1, indicative of a critical role of NMDA receptors in this effect. Interestingly, weaker TBS induction protocols resulted in synaptic depression in both l-V1 and m-V1, an effect that was blocked by MK 801 only in m-V1. Finally, dLGN stimulation also elicited long-latency fPSPs in the V1 contralateral to the stimulation site, likely reflecting polysynaptic activity crossing the midline via callosal fibers. Relative to ipsilateral recordings, contralateral fPSPs showed greater LTP in both V1 segments, which could not be blocked by MK 801 administration. Together, these data reveal clear differences in the expression of LTP at synapses in l-V1 and m-V1, with greater plasticity in the lateral V1 segment. Further, we confirm that NMDA receptors mediate some, but not all forms of synaptic plasticity in the V1 of adult rodents.
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Nuñez A, Domínguez S, Buño W, Fernández de Sevilla D. Cholinergic-mediated response enhancement in barrel cortex layer V pyramidal neurons. J Neurophysiol 2012; 108:1656-68. [PMID: 22723675 DOI: 10.1152/jn.00156.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neocortical cholinergic activity plays a fundamental role in sensory processing and cognitive functions, but the underlying cellular mechanisms are largely unknown. We analyzed the effects of acetylcholine (ACh) on synaptic transmission and cell excitability in rat "barrel cortex" layer V (L5) pyramidal neurons in vitro. ACh through nicotinic and M1 muscarinic receptors enhanced excitatory postsynaptic currents and through nicotinic and M2 muscarinic receptors reduced inhibitory postsynaptic currents. These effects increased excitability and contributed to the generation of Ca(2+) spikes and bursts of action potentials (APs) when inputs in basal dendrites were stimulated. Ca(2+) spikes were mediated by activation of NMDA receptors (NMDARs) and L-type voltage-gated Ca(2+) channels. Additionally, we demonstrate in vivo that basal forebrain stimulation induced an atropine-sensitive increase of L5 AP responses evoked by vibrissa deflection, an effect mainly due to the enhancement of an NMDAR component. Therefore, ACh modified the excitatory/inhibitory balance and switched L5 pyramidal neurons to a bursting mode that caused a potent and sustained response enhancement with possible fundamental consequences for the function of the barrel cortex.
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Affiliation(s)
- Angel Nuñez
- Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, 28029 Madrid, Spain
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Erasing synapses in sleep: is it time to be SHY? Neural Plast 2012; 2012:264378. [PMID: 22530156 PMCID: PMC3317003 DOI: 10.1155/2012/264378] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 12/04/2011] [Indexed: 02/04/2023] Open
Abstract
Converging lines of evidence strongly support a role for sleep in brain plasticity. An elegant idea that may explain how sleep accomplishes this role is the "synaptic homeostasis hypothesis (SHY)." According to SHY, sleep promotes net synaptic weakening which offsets net synaptic strengthening that occurs during wakefulness. SHY is intuitively appealing because it relates the homeostatic regulation of sleep to an important function (synaptic plasticity). SHY has also received important experimental support from recent studies in Drosophila melanogaster. There remain, however, a number of unanswered questions about SHY. What is the cellular mechanism governing SHY? How does it fit with what we know about plasticity mechanisms in the brain? In this review, I discuss the evidence and theory of SHY in the context of what is known about Hebbian and non-Hebbian synaptic plasticity. I conclude that while SHY remains an elegant idea, the underlying mechanisms are mysterious and its functional significance unknown.
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Hager AM, Dringenberg HC. Training-induced plasticity in the visual cortex of adult rats following visual discrimination learning. Learn Mem 2010; 17:394-401. [DOI: 10.1101/lm.1787110] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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