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Hippocampus and retrieval

Sheng-Chiang Wang, Chen-Cheng Lin, Chun-Chuan Chen, Nian-Sheng Tzeng, Yia-Ping Liu
Posttraumatic stress disorder (PTSD) is a trauma-induced mental disorder characterized by fear extinction abnormalities, which involve biological dysfunctions among fear circuit areas in the brain. Oxytocin (OXT) is a neuropeptide that regulates sexual reproduction and social interaction and has recently earned specific attention due to its role in adjusting neurobiological and behavioral correlates of PTSD; however, the mechanism by which this is achieved remains unclear. The present study aimed to examine whether the effects of OXT on traumatic stress-induced abnormalities of fear extinction (specifically induced by single prolonged stress (SPS), an animal model of PTSD) are associated with pro-inflammatory cytokines...
December 3, 2018: International Journal of Molecular Sciences
Kennett D Radford, Thomas Y Park, Shalini Jaiswal, Hongna Pan, Andrew Knutsen, Michael Zhang, Mercedes Driscoll, Lisa A Osborne-Smith, Bernard J Dardzinski, Kwang H Choi
Ketamine is a multimodal dissociative anesthetic, which provides powerful analgesia for victims with traumatic injury. However, the impact of ketamine administration in the peri-trauma period on the development of post-traumatic stress disorder (PTSD) remains controversial. Moreover, there is a major gap between preclinical and clinical studies because they utilize different doses and routes of ketamine administration. Here, we investigated the effects of sub-anesthetic doses of intravenous (IV) ketamine infusion on fear memory and brain glucose metabolism (BGluM) in rats...
November 30, 2018: Translational Psychiatry
Yingwei Zheng, Shouya Feng, Xutao Zhu, Wentao Jiang, Pengjie Wen, Feiyang Ye, Xiaoping Rao, Sen Jin, Xiaobin He, Fuqiang Xu
The mammalian basal forebrain (BF), a heterogenous structure providing the primary cholinergic inputs to cortical and limbic structures, plays a crucial role in various physiological processes such as learning/memory and attention. Despite the involvement of the BF cholinergic neurons (BFCNs) in olfaction related memory has been reported, the underlying neural circuits remain poorly understood. Here, we combined viral trans-synaptic tracing systems and ChAT-cre transgenic mice to systematically reveal the relationship between the olfactory system and the different subsets of BFCNs...
2018: Frontiers in Neural Circuits
Tirzah Kreisel, Brachi Wolf, Eli Keshet, Tamar Licht
Neurogenic roles of microglia (MG) are thought to include an active role in adult hippocampal neurogenesis in addition to their established roles in pruning surplus dendrites and clearing dead neuroblasts. However, identification of such a role and its delineation in the neurogenic cascade is yet to be established. Using diphtheria toxin-aided MG ablation, we show that MG reduction in the DG-the site where neuronal stem cells (NSCs) reside-is sufficient to impede overall hippocampal neurogenesis due to reduced survival of newly formed neuroblasts...
November 19, 2018: Glia
Yudan Ren, Vinh T Nguyen, Saurabh Sonkusare, Jinglei Lv, Tianji Pang, Lei Guo, Simon B Eickhoff, Michael Breakspear, Christine C Guo
Human interactions with the world are influenced by memories of recent events. This effect, often triggered by perceptual cues, occurs naturally and without conscious effort. However, the neuroscience of involuntary memory in a dynamic milieu has received much less attention than the mechanisms of voluntary retrieval with deliberate purpose. Here, we investigate the neural processes driven by naturalistic cues that relate to, and presumably trigger the retrieval of recent experiences. Viewing the continuation of recently viewed clips evokes greater bilateral activation in anterior hippocampus, precuneus and angular gyrus than naïve clips...
November 19, 2018: Nature Communications
Laura Serra, Marco Bozzali, Lucia Fadda, Maria Stefania De Simone, Michela Bruschini, Roberta Perri, Carlo Caltagirone, Giovanni A Carlesimo
The role of the hippocampus and neocortical areas in the retrieval of past memories in pre-dementia Alzheimer's disease (AD) patients was investigated. The aim was to assess whether the hippocampus has a temporary role in memory trace formation, according to the Cortical Reallocation Theory (CRT), or whether it continuously updates and enriches memories, according to the Multiple Trace Theory. According to the former theory, hippocampal damage should affect more recent memories, whereas the association cortex is expected to affect memories of the entire lifespan...
November 19, 2018: Journal of Neuropsychology
Kamilla Irigaray Torquatto, Ana Paula Menegolla, Bruno Popik, Mirelle Araujo Casagrande, Lucas de Oliveira Alvares
The role of the calcium-permeable AMPA receptor (CP-AMPAR) in synaptic plasticity is well established. CP-AMPAR is believed to be recruited to synapse when the memory trace is in a plastic state; however, the direct implications of its expression for memory processes is less known. Here, we investigated the contribution of CP-AMPAR expressed in the basolateral amygdala (BLA) and hippocampus (HPC) in consolidation of different types of memory, retrieval and memory update. We showed that CP-AMPAR blockade by NASPM in the BLA and HPC impaired fear memory consolidation...
October 26, 2018: Neuropharmacology
Molly S Hermiller, Stephen VanHaerents, Tommi Raij, Joel L Voss
Episodic memory is thought to rely on interactions of the hippocampus with other regions of the distributed hippocampal-cortical network (HCN) via interregional activity synchrony in the theta frequency band. We sought to causally test this hypothesis using network-targeted transcranial magnetic stimulation. Healthy humans participants completed four experimental sessions, each involving a different stimulation pattern delivered to the same individualized parietal cortex location of the HCN for all sessions...
November 17, 2018: Hippocampus
Ruud M W J Berkers, Matthias Ekman, Eelco V van Dongen, Atsuko Takashima, Markus Barth, Ken A Paller, Guillén Fernández
Memory reprocessing following acquisition enhances memory consolidation. Specifically, neural activity during encoding is thought to be 'replayed' during subsequent slow-wave sleep. Such memory replay is thought to contribute to the functional reorganization of neural memory traces. In particular, memory replay may facilitate the exchange of information across brain regions by inducing a reconfiguration of connectivity across the brain. Memory reactivation can be induced by external cues through a procedure known as "targeted memory reactivation"...
November 16, 2018: Scientific Reports
Bita Beigi, Siamak Shahidi, Alireza Komaki, Abdolrahman Sarihi, Nasrin Hashemi-Firouzi
BACKGROUND: Learning and memory are among the most important cognitive functions of the brain. Melatonin receptor type 2 (MT2R) is located in the hippocampus and participates in learning and memory processes. In the present study, we examined the role of hippocampal MT2R activation in the acquisition, consolidation, and retrieval of learning and memory in novel object recognition (NOR) and passive avoidance (PA) tasks. METHODS: IIK7 (0.03, 0.3, and 3 μg/μl/side), as a selective MT2R agonist, or vehicle was injected bilaterally into the dentate gyrus (DG) region of the hippocampus in rats five minutes before training, immediately after training, and five minutes before the retrieval-behavioral tasks, respectively...
November 15, 2018: International Journal of Neuroscience
Björn H Schott, Torsten Wüstenberg, Eva Lücke, Ina-Maria Pohl, Anni Richter, Constanze I Seidenbecher, Stefan Pollmann, Jasmin M Kizilirmak, Alan Richardson-Klavehn
Activation of parietal cortex structures like the precuneus is commonly observed during explicit memory retrieval, but the role of parietal cortices in encoding has only recently been appreciated and is still poorly understood. Considering the importance of the precuneus in human visual attention and imagery, we aimed to assess a potential role for the precuneus in the encoding of visuospatial representations into long-term memory. We therefore investigated the acquisition of constant versus repeatedly shuffled configurations of icons on background images over five subsequent days in 32 young, healthy volunteers...
November 15, 2018: Human Brain Mapping
Anuck Sawangjit, Carlos N Oyanedel, Niels Niethard, Carolina Salazar, Jan Born, Marion Inostroza
There is a long-standing division in memory research between hippocampus-dependent memory and non-hippocampus-dependent memory, as only the latter can be acquired and retrieved in the absence of normal hippocampal function1,2 . Consolidation of hippocampus-dependent memory, in particular, is strongly supported by sleep3-5 . Here we show that the formation of long-term representations in a rat model of non-hippocampus-dependent memory depends not only on sleep but also on activation of a hippocampus-dependent mechanism during sleep...
November 14, 2018: Nature
Asaf Gilboa, Melanie Sekeres, Morris Moscovitch, Gordon Winocur
The hippocampus supports flexible decision-making through memory integration: bridging across episodes and inferring associations between stimuli that were never presented together (associative inference). A pre-requisite for memory integration is flexible representations of the relationships between stimuli within episodes (AB) but also of the constituent units (A,B). Here we investigated whether the hippocampus is required for parsing experienced episodes into their constituents to infer their re-combined within-episode associations (dissociative inference)...
November 12, 2018: Hippocampus
Yuta Senzai
Anatomical observations, theoretical work and lesioning experiments have supported the idea that the CA3 in the hippocampus is important for encoding, storage and retrieval of memory while the dentate gyrus (DG) is important for the pattern separation of the incoming inputs from the entorhinal cortex. Study of the presumed function of the dentate gyrus in pattern separation has been hampered by the lack of reliable methods to identify different excitatory cell types in the DG. Recent papers have identified different cell types in the DG, in awake behaving animals, with more reliable methods...
November 5, 2018: Neuroscience Research
Elizabeth Ankudowich, Stamatoula Pasvanis, M Natasha Rajah
Altered functional connectivity between dorsolateral prefrontal cortex (DLPFC), posterior hippocampus (HC) and other brain regions with advanced age may contribute to age-related differences in episodic memory. In the current fMRI study of spatial context memory, we used seed connectivity analysis to test for age-related differences in the correlations between activity in DLPFC and HC seeds, and the rest of the brain, in an adult life span sample. In young adults, we found that connectivity between right DLPFC and other prefrontal cortex regions, parietal cortex, precuneus, and ventral visual cortices during encoding was positively related to performance...
November 8, 2018: Psychology and Aging
Federica Lucchelli, Maria Cristina Saetti, Hans Spinnler
A still unsettled issue of amnesia concerns the differential contributions to recall impairment of the underlying retrieval and storage abilities. The aim of the present study was to disentangle and to measure such roles in the recall of past public events comparing patients with degenerative amnesia and healthy elderly. The experiment included 44 healthy elderly and two groups of participants with degenerative amnesia, namely 17 patients with amnestic mild cognitive impairment and 22 mild Alzheimer's disease patients...
2018: Journal of Alzheimer's Disease: JAD
Karthik R Ramanathan, Jingji Jin, Thomas F Giustino, Martin R Payne, Stephen Maren
The thalamic nucleus reuniens (RE) receives dense projections from the medial prefrontal cortex (mPFC), interconnects the mPFC and hippocampus, and may serve a pivotal role in regulating emotional learning and memory. Here we show that the RE and its mPFC afferents are critical for the extinction of Pavlovian fear memories in rats. Pharmacological inactivation of the RE during extinction learning or retrieval increases freezing to an extinguished conditioned stimulus (CS); renewal of fear outside the extinction context was unaffected...
October 30, 2018: Nature Communications
Ahmed T Hussin, Timothy K Leonard, Kari L Hoffman
Sharp-wave ripples (SWRs) are spontaneous, synchronized neural population events in the hippocampus widely thought to play a role in memory consolidation and retrieval. They occur predominantly in sleep and quiet immobility, and in primates they also appear during active visual exploration. Typical measures of SWRs in behaving rats include changes in rate of occurrence, or in the incidence of specific neural ensemble activity contained within the categorical SWR event. Much less is known about the relevance of spatiotemporal SWR features, though they may index underlying activity of specific cell types including ensemble-specific internally generated sequences...
October 29, 2018: Hippocampus
Irene Y Huang, Yu-Luan Hsu, Chien-Chang Chen, Mei-Fang Chen, Zhi-Hong Wen, Hsien-Ting Huang, Ingrid Y Liu
Memory retrieval dysfunction is a symptom of schizophrenia, autism spectrum disorder (ASD), and absence epilepsy (AE), as well as an early sign of Alzheimer's disease. To date, few drugs have been reported to enhance memory retrieval. Here, we found that a coral-derived natural product, excavatolide-B (Exc-B), enhances contextual memory retrieval in both wild-type and Cav 3.2-/- mice via repressing the delayed rectifier potassium current, thus lowering the threshold for action potential initiation and enhancing induction of long-term potentiation (LTP)...
October 25, 2018: Marine Drugs
Hannah R Joo, Loren M Frank
Various cognitive functions have long been known to require the hippocampus. Recently, progress has been made in identifying the hippocampal neural activity patterns that implement these functions. One such pattern is the sharp wave-ripple (SWR), an event associated with highly synchronous neural firing in the hippocampus and modulation of neural activity in distributed brain regions. Hippocampal spiking during SWRs can represent past or potential future experience, and SWR-related interventions can alter subsequent memory performance...
December 2018: Nature Reviews. Neuroscience
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