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Kant D, Jha SK. The formation of compensatory contextual fear memory in the absence of dorsal hippocampus does not change sleep architecture. Behav Brain Res 2019; 370:111944. [PMID: 31100300 DOI: 10.1016/j.bbr.2019.111944] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 05/11/2019] [Accepted: 05/13/2019] [Indexed: 10/26/2022]
Abstract
Although the dorsal hippocampus (DH) plays an essential role in the consolidation of contextual fear-conditioned (CxFC) memory, this consolidation may also occur in the absence of DH. It is, however, not known if the development of a compensatory circuit for CxFC memory is time-dependent. The DH-dependent contextual fear memory influences sleep architecture, but whether the compensatory fear memory can influence sleep, is not known. Here, we have studied (a) the temporal progression of compensatory contextual fear memory in the absence of DH and (b) the influence of compensatory contextual fear memory on sleep architecture. Rats were surgically prepared for chronic polysomnographic recordings and drug injections in the DH. They were divided into four groups: DH-non-lesioned and fear-conditioned, DH-non-lesioned and non-fear-conditioned, DH-lesioned and fear-conditioned and DH-lesioned and non-fear-conditioned groups. The DH was lesioned with ibotenic acid. The animals were conditioned to contextual fear twice: 1st training on Day 5 and testing on Day 6; 2nd training on Day 10 and testing on Day 11. The DH-lesioned and fear-conditioned animals did not exhibit freezing response during the first testing but showed a robust freezing response when re-trained after a gap of three days. In addition, wakefulness and NREM sleep amount did not change, but REM sleep significantly decreased in the DH-dependent CxFC memory group. Interestingly, REM sleep did not decrease in the DH-independent CxFC memory group. Our findings suggest that the development of compensatory CxFC memory is a time-dependent process and the compensatory CxFC memory may not influence sleep architecture.
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Affiliation(s)
- Deepika Kant
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Sushil K Jha
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.
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Influence of cued-fear conditioning and its impairment on NREM sleep. Neurobiol Learn Mem 2017; 144:155-165. [PMID: 28733208 DOI: 10.1016/j.nlm.2017.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 05/30/2017] [Accepted: 07/15/2017] [Indexed: 01/03/2023]
Abstract
Many studies suggest that fear conditioning influences sleep. It is, however, not known if the changes in sleep architecture after fear conditioning are essentially associated with the consolidation of fearful memory or with fear itself. Here, we have observed that within sleep, NREM sleep consistently remained augmented after the consolidation of cued fear-conditioned memory. But a similar change did not occur after impairing memory consolidation by blocking new protein synthesis and glutamate transmission between glial-neuronal loop in the lateral amygdala (LA). Anisomycin (a protein synthesis inhibitor) and DL-α-amino-adipic acid (DL- α -AA) (a glial glutamine synthetase enzyme inhibitor) were microinjected into the LA soon after cued fear-conditioning to induce memory impairment. On the post-conditioning day, animals in both the groups exhibited significantly less freezing. In memory-consolidated groups (vehicle groups), NREM sleep significantly increased during 2nd to 5th hours after training compared to their baseline days. However, in memory impaired groups (anisomycin and DL- α -AA microinjected groups), similar changes were not observed. Our results thus suggest that changes in sleep architecture after cued fear-conditioning are indeed a consolidation dependent event.
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Headley DB, Weinberger NM. Relational associative learning induces cross-modal plasticity in early visual cortex. Cereb Cortex 2015; 25:1306-18. [PMID: 24275832 PMCID: PMC4397573 DOI: 10.1093/cercor/bht325] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Neurobiological theories of memory posit that the neocortex is a storage site of declarative memories, a hallmark of which is the association of two arbitrary neutral stimuli. Early sensory cortices, once assumed uninvolved in memory storage, recently have been implicated in associations between neutral stimuli and reward or punishment. We asked whether links between neutral stimuli also could be formed in early visual or auditory cortices. Rats were presented with a tone paired with a light using a sensory preconditioning paradigm that enabled later evaluation of successful association. Subjects that acquired this association developed enhanced sound evoked potentials in their primary and secondary visual cortices. Laminar recordings localized this potential to cortical Layers 5 and 6. A similar pattern of activation was elicited by microstimulation of primary auditory cortex in the same subjects, consistent with a cortico-cortical substrate of association. Thus, early sensory cortex has the capability to form neutral stimulus associations. This plasticity may constitute a declarative memory trace between sensory cortices.
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Affiliation(s)
- Drew B Headley
- Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800, USA
| | - Norman M Weinberger
- Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800, USA
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Vakalopoulos C. The EEG as an index of neuromodulator balance in memory and mental illness. Front Neurosci 2014; 8:63. [PMID: 24782698 PMCID: PMC3986529 DOI: 10.3389/fnins.2014.00063] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/18/2014] [Indexed: 11/24/2022] Open
Abstract
There is a strong correlation between signature EEG frequency patterns and the relative levels of distinct neuromodulators. These associations become particularly evident during the sleep-wake cycle. The monoamine-acetylcholine balance hypothesis is a theory of neurophysiological markers of the EEG and a detailed description of the findings that support this proposal are presented in this paper. According to this model alpha rhythm reflects the relative predominance of cholinergic muscarinic signals and delta rhythm that of monoaminergic receptor effects. Both high voltage synchronized rhythms are likely mediated by inhibitory Gαi/o-mediated transduction of inhibitory interneurons. Cognitively, alpha and delta EEG measures are proposed to indicate automatic and flexible strategies, respectively. Sleep is associated with marked changes in relative neuromodulator levels corresponding to EEG markers of distinct stages. Sleep studies on memory consolidation present some of the strongest evidence yet for the respective roles of monoaminergic and cholinergic projections in declarative and non-declarative memory processes, a key theoretical premise for understanding the data. Affective dysregulation is reflected in altered EEG patterns during sleep.
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Kim D, Paré D, Nair SS. Mechanisms contributing to the induction and storage of Pavlovian fear memories in the lateral amygdala. Learn Mem 2013; 20:421-30. [PMID: 23864645 PMCID: PMC3718199 DOI: 10.1101/lm.030262.113] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 05/21/2013] [Indexed: 11/24/2022]
Abstract
The relative contributions of plasticity in the amygdala vs. its afferent pathways to conditioned fear remain controversial. Some believe that thalamic and cortical neurons transmitting information about the conditioned stimulus (CS) to the lateral amygdala (LA) serve a relay function. Others maintain that thalamic and/or cortical plasticity is critically involved in fear conditioning. To address this question, we developed a large-scale biophysical model of the LA that could reproduce earlier findings regarding the cellular correlates of fear conditioning in LA. We then conducted model experiments that examined whether fear memories depend on (1) training-induced increases in the responsiveness of thalamic and cortical neurons projecting to LA, (2) plasticity at the synapses they form in LA, and/or (3) plasticity at synapses between LA neurons. These tests revealed that training-induced increases in the responsiveness of afferent neurons are required for fear memory formation. However, once the memory has been formed, this factor is no longer required because the efficacy of the synapses that thalamic and cortical neurons form with LA cells has augmented enough to maintain the memory. In contrast, our model experiments suggest that plasticity at synapses between LA neurons plays a minor role in maintaining the fear memory.
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Affiliation(s)
- Dongbeom Kim
- Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211, USA
| | - Denis Paré
- Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, USA
| | - Satish S. Nair
- Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211, USA
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Mild Transient Hypercapnia as a Novel Fear Conditioning Stimulus Allowing Re-Exposure during Sleep. PLoS One 2013; 8:e67435. [PMID: 23840700 PMCID: PMC3693948 DOI: 10.1371/journal.pone.0067435] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 05/20/2013] [Indexed: 12/31/2022] Open
Abstract
Introduction Studies suggest that sleep plays a role in traumatic memories and that treatment of sleep disorders may help alleviate symptoms of posttraumatic stress disorder. Fear-conditioning paradigms in rodents are used to investigate causal mechanisms of fear acquisition and the relationship between sleep and posttraumatic behaviors. We developed a novel conditioning stimulus (CS) that evoked fear and was subsequently used to study re-exposure to the CS during sleep. Methods Experiment 1 assessed physiological responses to a conditioned stimulus (mild transient hypercapnia, mtHC; 3.0% CO2; n = 17)+footshock for the purpose of establishing a novel CS in male FVB/J mice. Responses to the novel CS were compared to tone+footshock (n = 18) and control groups of tone alone (n = 17) and mild transient hypercapnia alone (n = 10). A second proof of principle experiment re-exposed animals during sleep to mild transient hypercapnia or air (control) to study sleep processes related to the CS. Results Footshock elicited a response of acute tachycardia (30–40 bpm) and increased plasma epinephrine. When tone predicted footshock it elicited mild hypertension (1–2 mmHg) and a three-fold increase in plasma epinephrine. When mtHC predicted footshock it also induced mild hypertension, but additionally elicited a conditioned bradycardia and a smaller increase in plasma epinephrine. The overall mean 24 hour sleep–wake profile was unaffected immediately after fear conditioning. Discussion Our study demonstrates the efficacy of mtHC as a conditioning stimulus that is perceptible but innocuous (relative to tone) and applicable during sleep. This novel model will allow future studies to explore sleep-dependent mechanisms underlying maladaptive fear responses, as well as elucidate the moderators of the relationship between fear responses and sleep.
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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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Total sleep deprivation impairs the encoding of trace-conditioned memory in the rat. Neurobiol Learn Mem 2011; 95:355-60. [DOI: 10.1016/j.nlm.2011.01.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 12/25/2010] [Accepted: 01/25/2011] [Indexed: 12/30/2022]
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Transient changes in frontal alpha asymmetry as a measure of emotional and physical distress during sleep. Brain Res 2011; 1367:234-49. [DOI: 10.1016/j.brainres.2010.09.090] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 09/24/2010] [Accepted: 09/25/2010] [Indexed: 11/22/2022]
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The medial geniculate, not the amygdala, as the root of auditory fear conditioning. Hear Res 2010; 274:61-74. [PMID: 20466051 DOI: 10.1016/j.heares.2010.03.093] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 03/25/2010] [Accepted: 03/27/2010] [Indexed: 11/23/2022]
Abstract
The neural basis of auditory fear conditioning (AFC) is almost universally believed to be the amygdala, where auditory fear memories are reputedly acquired and stored. This widely-accepted amygdala model holds that the auditory conditioned stimulus (CS) and the nociceptive unconditioned stimulus (US) first converge in the lateral nucleus of the amygdala (AL), and are projected independently to it from the medial division of the medial geniculate nucleus (MGm) and the adjacent posterior intralaminar nucleus (PIN), which serve merely as sensory relays. However, the four criteria that are used to support the AL model, (a) CS-US convergence, (b) associative plasticity, (c) LTP and (d) lesion-induced learning impairment, are also met by the MGm/PIN. Synaptic and molecular approaches supporting the AL also implicate the MGm/PIN. As both the AL and its preceding MGm/PIN are critically involved, we propose that the latter be considered the "root" of AFC.
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Wamsley EJ, Antrobus JS. The expression of trace conditioning during non-REM sleep and its relation to subjective experience. Neurobiol Learn Mem 2009; 92:283-91. [DOI: 10.1016/j.nlm.2009.02.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 02/03/2009] [Accepted: 02/21/2009] [Indexed: 11/29/2022]
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Hennevin E, Huetz C, Edeline JM. Neural representations during sleep: From sensory processing to memory traces. Neurobiol Learn Mem 2007; 87:416-40. [PMID: 17178239 DOI: 10.1016/j.nlm.2006.10.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2006] [Revised: 10/20/2006] [Accepted: 10/26/2006] [Indexed: 10/23/2022]
Abstract
In the course of a day, the brain undergoes large-scale changes in functional modes, from attentive wakefulness to the deepest stage of sleep. The present paper evaluates how these state changes affect the neural bases of sensory and cognitive representations. Are organized neural representations still maintained during sleep? In other words, despite the absence of conscious awareness, do neuronal signals emitted during sleep contain information and have a functional relevance? Through a critical evaluation of the animal and human literature, neural representations at different levels of integration (from the most elementary sensory level to the most cognitive one) are reviewed. Recordings of neuronal activity in animals at presentation of neutral or significant stimuli show that some analysis of the external word remains possible during sleep, allowing recognition of behaviorally relevant stimuli. Event-related brain potentials in humans confirm the preservation of some sensory integration and discriminative capacity. Behavioral and neuroimaging studies in humans substantiate the notion that memory representations are reactivated and are reorganized during post-learning sleep; these reorganisations may account for the beneficial effects of sleep on behavioral performance. Electrophysiological results showing replay of neuronal sequences in animals are presented, and their relevance as neuronal correlates of memory reactivation is discussed. The reviewed literature provides converging evidence that structured neural representations can be activated during sleep. Which reorganizations unique to sleep benefit memory representations, and to what extent the operations still efficient in processing environmental information during sleep are similar to those underlying the non-conscious, automatic processing continually at work in wakefulness, are challenging questions open to investigation.
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Affiliation(s)
- Elizabeth Hennevin
- Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, UMR CNRS 8620, Université Paris-Sud, Bâtiment 446, 91405 Orsay Cedex, France.
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