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Hippocampus and retrieval

Susumu Takahashi
In our minds we can vividly re-experience a series of past events or episodes that occurred along space and time. In 1957, a highly influential clinical investigation published by Scoville and Milner suggested that episodic memory retrieval is severely impaired after physical damage occurs to the hippocampus. In fact, loss of the hippocampus can lead to a profound disturbance to spatial navigation. Within the hippocampus reside place cells: excitatory pyramidal cells that maximally fire at a particular location...
2018: Advances in Neurobiology
Roger Marek, Pankaj Sah
The activity of neural circuits that underpin particular behaviours are one of the most interesting questions in neurobiology today. This understanding will not only lead to a detailed understanding of learning and memory formation, but also provides a platform for the development of novel therapeutic approaches to a range of neurological disorders that afflict humans. Among the different behavioural paradigms, Pavlovian fear conditioning and its extinction are two of the most extensively used to study acquisition, consolidation and retrieval of fear-related memories...
2018: Advances in Neurobiology
Fiorenza Stagni, Andrea Giacomini, Marco Emili, Beatrice Uguagliati, Maria Paola Bonasoni, Renata Bartesaghi, Sandra Guidi
Intellectual disability in Down syndrome (DS) has been attributed to neurogenesis impairment during fetal brain development. Consistently with explicit memory alterations observed in children with DS, fetuses with DS exhibit neurogenesis impairment in the hippocampus, a key region involved in memory formation and consolidation. Recent evidence suggests that the subiculum plays a unique role in memory retrieval, a process that is also altered in DS. While much attention has been devoted to the hippocampus, there is a striking lack of information regarding the subiculum of individuals with DS and DS models...
October 16, 2018: Brain Pathology
Roksana SoukhakLari, Leila Moezi, Fatema Pirsalami, Nahid Ashjazadeh, Maryam Moosavi
The loss of cholinergic neurons has been a major issue in researches on Alzheimer's disease (AD) for about 40 years. Therefore, the scopolamine model of amnesia has been widely used in AD researches. Recently, it was reported that the early stage amnesia of AD is related to memory retrieval deficit. Curcumin, as the main ingredient of turmeric, has been suggested to decrease the prevalence of AD in human population. This study was conducted to assess if curcumin prevents retrieval deficit induced by scopolamine in passive avoidance task...
October 12, 2018: European Journal of Pharmacology
Shira Meir Drexler, Christian J Merz, Oliver T Wolf
Extinction learning, which creates new safety associations, is thought to be the mechanism underlying exposure therapy, commonly used for the treatment of anxiety disorders and posttraumatic stress disorder. The relative strength and availability for retrieval of both the fear and safety memories determine the response in a given situation. While the fear memory is often context-independent and may easily generalize, extinction memory is highly context-specific. "Renewal" of the extinguished fear memory might thus occur following a shift in context...
November 2018: Behavior Therapy
Tanya R Jonker, Halle Dimsdale-Zucker, Maureen Ritchey, Alex Clarke, Charan Ranganath
Remembering is a complex process that involves recalling specific details, such as who you were with when you celebrated your last birthday, as well as contextual information, such as the place where you celebrated. It is well established that the act of remembering enhances long-term retention of the retrieved information, but the neural and cognitive mechanisms that drive memory enhancement are not yet understood. One possibility is that the process of remembering results in reactivation of the broader episodic context...
October 8, 2018: Proceedings of the National Academy of Sciences of the United States of America
Marius Rosier, Léa Le Barillier, David Meunier, Malika El Yacoubi, Gaël Malleret, Paul-Antoine Salin
Study Objectives: Paradoxical sleep (PS) has been shown to play an important role in memory, in particular in emotional memory processes. However, the involvement of this particular sleep stage in the systemic consolidation of remote (30 days old) memory has never been tested. We examined whether post-learning PS could play a role in the consolidation of remote fearful memory and in the brain network reorganization that depends on it. Methods: Mice were PS-deprived during 6 hours after contextual fear conditioning using an automated method, and their memory was tested either 1 day or 30 days after learning...
October 4, 2018: Sleep
Karthik R Ramanathan, Reed L Ressler, Jingji Jin, Stephen Maren
The nucleus reuniens (RE) is a ventral midline thalamic nucleus that interconnects the medial prefrontal cortex (mPFC) and hippocampus (HPC). Considerable data indicate that HPC-mPFC circuits are involved in contextual and spatial memory; however, it is not clear whether the RE mediates the acquisition or retrieval of these memories. To examine this question, we inactivated the RE with muscimol before either the acquisition or retrieval of Pavlovian fear conditioning in rats; freezing served as the index of fear...
October 3, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
McKenzie J Fannon, Karthik K Mysore, Jefferson Williams, Leon W Quach, Dvijen C Purohit, Britta D Sibley, Janna S Sage-Sepulveda, Khush M Kharidia, Roberto J Morales Silva, Michael J Terranova, Sucharita S Somkuwar, Miranda C Staples, Chitra D Mandyam
Adult male and female GFAP-TK transgenic rats experienced six weeks of chronic intermittent ethanol vapor inhalation (CIE). During the last week of CIE, a subset of male and female TK rats were fed with Valcyte to ablate neural progenitor cells (NPCs). Seventy-two hours after CIE cessation, all CIE and age-matched ethanol naïve controls experienced auditory trace fear conditioning (TFC). Twenty-four hours later all animals were tested for cue-mediated retrieval in the fear context. Adult male CIE rats showed a significant burst in NPCs paralleled by reduction in fear retrieval compared to naïve controls and Valcyte treated CIE rats...
September 28, 2018: Neuropharmacology
Espen Langnes, Didac Vidal-Piñeiro, Markus H Sneve, Inge K Amlien, Kristine B Walhovd, Anders M Fjell
Change in hippocampal function is a major factor in life span development and decline of episodic memory. Evidence indicates a long-axis specialization where anterior hippocampus is more engaged during encoding than during retrieval, and posterior more engaged during retrieval than during encoding. We tested the life span trajectory of hippocampal long-axis episodic memory-related activity and functional connectivity (FC) in 496 participants (6.8-80.8 years) encoding and retrieving associative memories. We found evidence for a long-axis encoding-retrieval specialization that declined linearly during development and aging, eventually vanishing in the older adults...
October 1, 2018: Cerebral Cortex
Xi Zhu, Benjamin Suarez-Jimenez, Amit Lazarov, Liat Helpman, Santiago Papini, Ari Lowell, Ariel Durosky, Martin A Lindquist, John C Markowitz, Franklin Schneier, Tor D Wager, Yuval Neria
BACKGROUND: Recent research suggests that posttraumatic stress disorder (PTSD) is associated with altered amygdala and hippocampal resting-state functional connectivity (rsFC). However, less research has examined whether Prolonged Exposure (PE), a first line exposure-based treatment for PTSD, has the potential to alter resting state neural networks. METHODS: A total of 24 patients with PTSD and 26 matched trauma-exposed healthy controls (TEHCs) underwent resting-state functional magnetic resonance imaging (fMRI) at baseline...
October 2018: Depression and Anxiety
Travis D Goode, Stephen Maren
BACKGROUND: Comorbidity of anxiety disorders, stressor- and trauma-related disorders, and substance use disorders is extremely common. Moreover, therapies that reduce pathological fear and anxiety on the one hand, and drug-seeking on the other, often prove short-lived and are susceptible to relapse. Considerable advances have been made in the study of the neurobiology of both aversive and appetitive extinction, and this work reveals shared neural circuits that contribute to both the suppression and relapse of conditioned responses associated with trauma or drug use...
September 25, 2018: Psychopharmacology
Nicole A Guitar, David F Sherry
Adult hippocampal neurogenesis has been proposed to both aid memory formation and disrupt memory. We examined the role of adult hippocampal neurogenesis in spatial working and reference memory in black-capped chickadees (Poecile atricapillus), a passerine bird that relies on spatial memory for cache retrieval and foraging. We tested spatial working and spatial reference memory in birds that had received methylazoxymethanol acetate (MAM), a neurotoxin that decreases hippocampal neurogenesis. MAM treatment significantly reduced neurogenesis in the hippocampus quantified by doublecortin (DCX) labeling of newly divided and migrating neurons...
September 24, 2018: Developmental Neurobiology
Da Song, Qinghu Yang, Yiran Lang, Zhaosen Wen, Zhen Xie, Da Zheng, Tianyi Yan, Yujun Deng, Hiroshi Nakanishi, Zhenzhen Quan, Hong Qing
The CA3 subregion of the hippocampus is important for rapid encoding, storage and retrieval of associative memories. Lesions and pharmacological inhibitions of hippocampal CA3 suggest that it is essential for different memories. However, how CA3 functions in spatial and episodic memory in different time scales (i.e. short-term versus long term) without permanent lesions has not been systematically investigated yet. Taking advantage of the chemogenetic access to opsins, this study used luminopsins, fusion proteins of luciferase and optogenetic elements, to manipulate neuronal activity in CA3 during memory tasks over a range of spatial and temporal scales...
September 19, 2018: Neurobiology of Learning and Memory
Laura A Libby, Zachariah M Reagh, Nichole R Bouffard, J Daniel Ragland, Charan Ranganath
Episodic memory is known to rely on the hippocampus, but how the hippocampus organizes different episodes to permit their subsequent retrieval remains controversial. One major area of debate hinges on a discrepancy between two hypothesized roles of the hippocampus: differentiating between similar events to reduce interference and assigning similar representations to events that share overlapping items and contextual information. Here, we used multivariate analyses of activity patterns measured with fMRI to characterize how the hippocampus distinguishes between memories based on similarity at the level of items and/or context...
September 21, 2018: Journal of Cognitive Neuroscience
Raphael Koster, Martin J Chadwick, Yi Chen, David Berron, Andrea Banino, Emrah Düzel, Demis Hassabis, Dharshan Kumaran
Recent evidence challenges the widely held view that the hippocampus is specialized for episodic memory, by demonstrating that it also underpins the integration of information across experiences. Contemporary computational theories propose that these two contrasting functions can be accomplished by big-loop recurrence, whereby the output of the system is recirculated back into the hippocampus. We use ultra-high-resolution fMRI to provide support for this hypothesis, by showing that retrieved information is presented as a new input on the superficial entorhinal cortex-driven by functional connectivity between the deep and superficial entorhinal layers...
September 19, 2018: Neuron
Jozien Goense
Memory encoding and retrieval require directional exchange of information between different areas in the medial temporal lobe. In this issue of Neuron, Koster et al. (2018) use high-resolution fMRI combined with state-of-the-art data analysis methods to trace the information flow in memory circuits in hippocampus and entorhinal cortex.
September 19, 2018: Neuron
Rebecca F Stevenson, Jie Zheng, Lilit Mnatsakanyan, Sumeet Vadera, Robert T Knight, Jack J Lin, Michael A Yassa
The hippocampus plays a critical role in spatial memory. However, the exact neural mechanisms underlying high-fidelity spatial memory representations are unknown. We report findings from presurgical epilepsy patients with bilateral hippocampal depth electrodes performing an object-location memory task that provided a broad range of spatial memory precision. During encoding, patients were shown a series of objects along the circumference of an invisible circle. At test, the same objects were shown at the top of the circle (0°), and patients used a dial to move the object to its location shown during encoding...
October 2, 2018: Proceedings of the National Academy of Sciences of the United States of America
Boyoung Lee, Eunyoung Bang, Won Suk Yang, Afshin Paydar, Go Eun Ha, Sujin Kim, Jong-Hyun Kim, Taesup Cho, Seung Eun Lee, Sukchan Lee, Myoung-Goo Kang, Eunji Cheong, Key-Sun Kim, Cheolju Lee, Myeong-Hee Yu, Hee-Sup Shin
Established fear memory becomes vulnerable to disruption after memory retrieval and extinction; this labile state is critical for inhibiting the return of fear memory. However, the labile state has a very narrow time window after retrieval, and underlying molecular mechanisms are not well known. To that end, we isolated the hippocampus immediately after fear memory retrieval and performed proteomics. We identified Neurobeachin (NBEA), an autism-related regulator of synaptic protein trafficking, to be upregulated after contextual fear memory retrieval...
September 13, 2018: Scientific Reports
Fiammetta Cosci, Giovanni Mansueto
Objective: Classifying mental disorders on the basis of objective makers might clarify their aetiology, help in making the diagnosis, identify "at risk" individuals, determine the severity of mental illness, and predict the course of the disorder. This study aims to review biological and clinical markers of panic disorder (PD). Methods: A computerized search was carried out in PubMed and Science Direct using the key words: "marker/biomarker/clinical marker/neurobiology/staging" combined using Boolean AND operator with "panic...
September 5, 2018: Psychiatry Investigation
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