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Hippocampus

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https://www.readbyqxmd.com/read/28188665/memory-for-relations-in-the-short-term-and-the-long-term-after-medial-temporal-lobe-damage
#1
Larry R Squire
A central idea about the organization of declarative memory and the function of the hippocampus is that the hippocampus provides for the coding of relationships between items. A question arises whether this idea refers to the process of forming long-term memory or whether, as some studies have suggested, memory for relations might depend on the hippocampus even at short retention intervals and even when the task falls within the province of short-term (working) memory. The latter formulation appears to place the operation of relational memory into conflict with the idea that working memory is independent of medial temporal lobe (MTL) structures...
February 11, 2017: Hippocampus
https://www.readbyqxmd.com/read/28188663/histamine-facilitates-gabaergic-transmission-in-the-rat-entorhinal-cortex-roles-of-h1-and-h2-receptors-na-permeable-cation-channels-and-inward-rectifier-k-channels
#2
Nicholas I Cilz, Saobo Lei
In the brain, histamine (HA) serves as a neuromodulator and a neurotransmitter released from the tuberomammillary nucleus (TMN). HA is involved in wakefulness, thermoregulation, energy homeostasis, nociception and learning and memory. The medial entorhinal cortex (MEC) receives inputs from the TMN and expresses HA receptors (H1 , H2 , and H3 ). We investigated the effects of HA on GABAergic transmission in the MEC and found that HA significantly increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) with an EC50 of 1...
February 11, 2017: Hippocampus
https://www.readbyqxmd.com/read/28188659/hippocampal-subfields-at-ultra-high-field-mri-an-overview-of-segmentation-and-measurement-methods
#3
Alessia Giuliano, Graziella Donatelli, Mirco Cosottini, Michela Tosetti, Alessandra Retico, Maria Evelina Fantacci
The hippocampus is one of the most interesting and studied brain regions because of its involvement in memory functions and its vulnerability in pathological conditions, such as neurodegenerative processes. In the recent years, the increasing availability of Magnetic Resonance Imaging (MRI) scanners that operate at ultra-high field (UHF), i.e. with static magnetic field strength ≥ 7T, has opened new research perspectives. Compared to conventional high-field scanners, these systems can provide new contrasts, increased signal-to-noise ratio and higher spatial resolution, thus they may improve the visualization of very small structures of the brain, such as the hippocampal subfields...
February 11, 2017: Hippocampus
https://www.readbyqxmd.com/read/28186683/corrigendum-dendrites-of-dentate-gyrus-granule-cells-contribute-to-pattern-separation-by-controlling-sparsity
#4
(no author information available yet)
No abstract text is available yet for this article.
February 10, 2017: Hippocampus
https://www.readbyqxmd.com/read/28177571/optimizing-for-generalization-in-the-decoding-of-internally-generated-activity-in-the-hippocampus
#5
Matthijs A A van der Meer, Alyssa A Carey, Youki Tanaka
The decoding of a sensory or motor variable from neural activity benefits from a known ground truth against which decoding performance can be compared. In contrast, the decoding of covert, cognitive neural activity, such as occurs in memory recall or planning, typically cannot be compared to a known ground truth. As a result, it is unclear how decoders of such internally generated activity should be configured in practice. We suggest that if the true code for covert activity is unknown, decoders should be optimized for generalization performance using cross-validation...
February 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28176459/reconsolidation-induced-rescue-of-a-remote-fear-memory-blocked-by-an-early-cortical-inhibition-involvement-of-the-anterior-cingulate-cortex-and-the-mediation-by-the-thalamic-nucleus-reuniens
#6
Rodrigo O Sierra, Lizeth K Pedraza, Querusche K Zanona, Fabiana Santana, Flávia Z Boos, Ana P Crestani, Josué Haubrich, Lucas de Oliveira Alvares, Maria Elisa Calcagnotto, Jorge A Quillfeldt
Systems consolidation is a time-dependent reorganization process involving neocortical and hippocampal networks underlying memory storage and retrieval. The involvement of the hippocampus during acquisition is well described, however we know much less about the concomitant contribution of cortical activity levels to the formation of stable remote memories. Here, after a reversible pharmacological inhibition of the anterior cingulate cortex (ACC) during the acquisition of a contextual fear conditioning, retrieval of both recent and remote memories were impaired, an effect that was reverted by a single memory reactivation session 48h after training, through a destabilization-dependent mechanism interpreted as reconsolidation, that restored the normal course of systems consolidation in order to rescue a remote memory...
February 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28176408/hippocampal-release-of-dopamine-and-norepinephrine-encodes-novel-contextual-information
#7
Moreno-Castilla Perla, Pérez-Ortega Rodrigo, Violante-Soria Valeria, Balderas Israela, Bermudez-Rattoni Federico
The detection and processing of novel information encountered in our environment is crucial for proper adaptive behavior and learning. Hippocampus is a prime structure for novelty detection that receives high-level inputs including context information. It is of our interest to understand the mechanisms by which the hippocampus processes contextual information. For this, we performed in vivo microdyalisis in order to monitor extracellular changes in neurotransmitter levels during Object Location Memory (OLM), a behavioral protocol developed to evaluate contextual information processing in recognition memory...
February 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28176400/effect-of-a-hallucinogenic-serotonin-5-ht2a-receptor-agonist-on-visually-guided-hippocampal-dependent-spatial-cognition-in-c57bl-6j-mice
#8
Gongliang Zhang, David Cinalli, Robert W Stackman
By acting on serotonin 5-HT2A receptors (5-HT2A Rs), serotonergic psychedelic drugs induce perceptual and visual hallucinations by increasing neuronal excitability and altering visual-evoked neuronal responses. The present study was designed to examine whether the perceptual alterations induced by a serotonergic psychedelic drug would affect the integrity of hippocampal-dependent, visually guided spatial cognition. phenylalkylamine hallucinogen TCB-2 is a selective agonist of 5-HT2A Rs. Mice received TCB-2 (1...
February 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28176397/a-scientific-theory-of-ars-memoriae-spatial-view-cells-in-a-continuous-attractor-network-with-linked-items
#9
Edmund T Rolls
The art of memory (ars memoriae) used since classical times includes using a well-known scene to associate each view or part of the scene with a different item in a speech. This memory technique is also known as the 'method of loci'. The new theory is proposed that this type of memory is implemented in the CA3 region of the hippocampus where there are spatial view cells in primates that allow a particular view to be associated with a particular object in an event or episodic memory. Given that the CA3 cells with their extensive recurrent collateral system connecting different CA3 cells, and associative synaptic modifiability, form an autoassociation or attractor network, the spatial view cells with their approximately Gaussian view fields become linked in a continuous attractor network...
February 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28100033/relaxin-3-inputs-target-hippocampal-interneurons-and-deletion-of-hilar-relaxin-3-receptors-in-floxed-rxfp3-mice-impairs-spatial-memory
#10
M Haidar, G Guèvremont, C Zhang, Rad Bathgate, E Timofeeva, C M Smith, A L Gundlach
Hippocampus is innervated by γ-aminobutyric acid (GABA) 'projection' neurons of the nucleus incertus (NI), including a population expressing the neuropeptide, relaxin-3 (RLN3). In studies aimed at gaining an understanding of the role of RLN3 signaling in hippocampus via its Gi/o -protein-coupled receptor, RXFP3, we examined the distribution of RLN3-immunoreactive nerve fibres and RXFP3 mRNA-positive neurons in relation to hippocampal GABA neuron populations. RLN3-positive elements were detected in close-apposition with a substantial population of somatostatin (SST)- and GABA-immunoreactive neurons, and a smaller population of parvalbumin- and calretinin-immunoreactive neurons in different hippocampal areas, consistent with the relative distribution patterns of RXFP3 mRNA and these marker transcripts...
January 18, 2017: Hippocampus
https://www.readbyqxmd.com/read/28100032/sequential-learning-during-contextual-fear-conditioning-guides-the-rate-of-systems-consolidation-implications-for-consolidation-of-multiple-memory-traces
#11
Lizeth K Pedraza, Rodrigo O Sierra, Ana P Crestani, Jorge A Quillfeldt, Lucas de Oliveira Alvares
Systems consolidation has been described as a time-dependent reorganization process involving the neocortical and hippocampal networks underlying memory storage and retrieval. Previous studies of our lab were able to demonstrate that systems consolidation is a dynamic process, rather than a merely passive, time-dependent phenomenon. Here, we studied the influence of sequential learning in contextual fear conditioning (CFC) with different training intensities in the time-course of hippocampal dependency and contextual specificity...
January 18, 2017: Hippocampus
https://www.readbyqxmd.com/read/28100031/impact-of-melatonin-receptor-signaling-on-zeitgeber-time-dependent-changes-in-cell-proliferation-and-apoptosis-in-the-adult-murine-hippocampus
#12
Michaela Fredrich, Mareike Hampel, Kay Seidel, Elmar Christ, Horst-Werner Korf
The hippocampus is subjected to diurnal/circadian rhythms on both the morphological and molecular levels. Certain aspects of cell proliferation in the adult hippocampus are regulated by melatonin and accompanied by apoptosis to ensure proper tissue maintenance and function. The present study investigated Zeitgeber time (ZT)-dependent changes in cell proliferation and apoptosis in the adult murine hippocampus and their regulation by melatonin receptor type1 and type2 (MT1/2)-mediated signaling. Adult melatonin-proficient C3H/HeN mice and melatonin-proficient (C3H/HeN) mice with targeted deletion of MT1/2 were adapted to a 12-hours light, 12-hours dark photoperiod and were sacrificed at ZT00, ZT06, ZT12, and ZT18...
January 18, 2017: Hippocampus
https://www.readbyqxmd.com/read/28100028/perirhinal-cortex-involvement-in-allocentric-spatial-learning-in-the-rat-evidence-from-doubly-marked-tasks
#13
Juan M J Ramos
It has recently been suggested that the different cortices of the medial temporal lobe support a mixture of object and spatial processing functions, challenging the anterior model that emphasized a strict functional differentiation between regions. However, for some structures, the perirhinal cortex (Prh) for example, a number of studies using lesion methods have shown a profound deficit exclusively in tasks involving object learning but not allocentric spatial learning. It may be that the learning paradigms used in previous studies have not been sensitive enough to detect a possible allocentric deficit in Prh-lesioned animals...
January 18, 2017: Hippocampus
https://www.readbyqxmd.com/read/28085212/identification-of-a-conserved-gene-signature-associated-with-an-exacerbated-inflammatory-environment-in-the-hippocampus-of-aging-rats
#14
Joaquín Pardo, Martin Abba, Ezequiel Lacunza, Laetitia Francelle, Gustavo R Morel, Tiago F Outeiro, Rodolfo G Goya
There have been a few descriptive studies in aged rodents about transcriptome changes in the hippocampus, most of them in males. Here, we assessed the age-changes in spatial memory performance and hippocampal morphology in female rats and compared those changes with changes in the hippocampal transcriptome. Old rats displayed significant deficits in spatial memory. In both age groups hole exploration frequency showed a clear peak at hole 0 (escape hole), but the amplitude of the peak was significantly higher in the young than in the old animals...
January 13, 2017: Hippocampus
https://www.readbyqxmd.com/read/28085210/disruption-of-amygdala-entorhinal-hippocampal-network-in-late-life-depression
#15
Stephanie L Leal, Jessica A Noche, Elizabeth A Murray, Michael A Yassa
Episodic memory deficits are evident in late-life depression (LLD) and are associated with subtle synaptic and neurochemical changes in the medial temporal lobes (MTL). However, the particular mechanisms by which memory impairment occurs in LLD are currently unknown. We tested older adults with (DS+) and without (DS-) depressive symptoms using high-resolution fMRI that is capable of discerning signals in hippocampal subfields and amygdala nuclei. Scanning was conducted during performance of an emotional discrimination task used previously to examine the relationship between depressive symptoms and amygdala-mediated emotional modulation of hippocampal pattern separation in young adults...
January 13, 2017: Hippocampus
https://www.readbyqxmd.com/read/28052448/the-can-in-network-a-biologically-inspired-model-for-self-sustained-theta-oscillations-and-memory-maintenance-in-the-hippocampus
#16
Francesco Giovannini, Beate Knauer, Motoharu Yoshida, Laure Buhry
During working memory tasks, the hippocampus exhibits synchronous theta-band activity, which is thought to be correlated with the short-term memory maintenance of salient stimuli. Recent studies indicate that the hippocampus contains the necessary circuitry allowing it to generate and sustain theta oscillations without the need of extrinsic drive. However, the cellular and network mechanisms supporting synchronous rhythmic activity are far from being fully understood. Based on electrophysiological recordings from hippocampal pyramidal CA1 cells, we present a possible mechanism for the maintenance of such rhythmic theta-band activity in the isolated hippocampus...
January 3, 2017: Hippocampus
https://www.readbyqxmd.com/read/28032686/impairments-in-spatial-representations-and-rhythmic-coordination-of-place-cells-in-the-3xtg-mouse-model-of-alzheimer-s-disease
#17
Alexandra J Mably, Brian J Gereke, Dylan T Jones, Laura Lee Colgin
Alzheimer's disease (AD) is an irreversible and highly progressive neurodegenerative disease. Clinically, patients with AD display impairments in episodic and spatial memory. However, the underlying neuronal dysfunctions that result in these impairments remain poorly understood. The hippocampus is crucial for spatial and episodic memory, and thus we tested the hypothesis that abnormal neuronal representations of space in the hippocampus contribute to memory deficits in AD. To test this hypothesis, we recorded spikes from place cells in hippocampal subfield CA1, together with corresponding rhythmic activity in local field potentials, in the 3xTg AD mouse model...
December 29, 2016: Hippocampus
https://www.readbyqxmd.com/read/28032685/the-dynamics-of-memory-consolidation-of-landmarks
#18
Janneke van Ekert, Joost Wegman, Clemens Jansen, Atsuko Takashima, Gabriele Janzen
Navigating through space is fundamental to human nature and requires the ability to retrieve relevant information from the remote past. With the passage of time, some memories become generic, capturing only a sense of familiarity. Yet, others maintain precision, even when acquired decades ago. Understanding the dynamics of memory consolidation is a major challenge to neuroscientists. Using functional magnetic resonance imaging, we systematically examined the effects of time and spatial context on the neural representation of landmark recognition memory...
December 29, 2016: Hippocampus
https://www.readbyqxmd.com/read/28032677/hippocampus-duality-memory-and-novelty-detection-are-subserved-by-distinct-mechanisms
#19
Emmanuel J Barbeau, Patrick Chauvel, Christopher J A Moulin, Jean Regis, Catherine Liégeois-Chauvel
The hippocampus plays a pivotal role both in novelty detection and in long-term memory. The physiological mechanisms underlying these behaviors have yet to be understood in humans. We recorded intracerebral evoked potentials within the hippocampus of epileptic patients (n=10) during both memory and novelty detection tasks (targets in oddball tasks). We found that memory and detection tasks elicited late local field potentials in the hippocampus during the same period (∼260-600 ms post stimulus onset, p < 0...
December 29, 2016: Hippocampus
https://www.readbyqxmd.com/read/28032676/hippocampal-gamma-band-synchrony-and-pupillary-responses-index-memory-during-visual-search
#20
Rodrigo Montefusco-Siegmund, Timothy K Leonard, Kari L Hoffman
Memory for scenes is supported by the hippocampus, among other interconnected structures, but the neural mechanisms related to this process are not well understood. To assess the role of the hippocampus in memory-guided scene search, we recorded local field potentials and multi-unit activity from the hippocampus of macaques as they performed goal-directed search tasks using natural scenes. We additionally measured pupil size during scene presentation, which in humans is modulated by recognition memory. We found that both pupil dilation and search efficiency accompanied scene repetition, thereby indicating memory for scenes...
December 29, 2016: Hippocampus
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