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Hippocampus

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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
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
https://www.readbyqxmd.com/read/28032674/parahippocampal-and-retrosplenial-connections-of-rat-posterior-parietal-cortex
#12
Grethe M Olsen, Shinya Ohara, Toshio Iijima, Menno P Witter
The posterior parietal cortex has been implicated in spatial functions, including navigation. The hippocampal and parahippocampal region and the retrosplenial cortex are crucially involved in navigational processes and connections between the parahippocampal/retrosplenial domain and the posterior parietal cortex have been described. However, an integrated account of the organization of these connections is lacking. Here we investigated parahippocampal connections of each posterior parietal subdivision and the neighboring secondary visual cortex using conventional retrograde and anterograde tracers as well as transsynaptic retrograde tracing with a modified rabies virus...
December 29, 2016: Hippocampus
https://www.readbyqxmd.com/read/28032672/hippocampal-damage-and-memory-impairment-in-congenital-cyanotic-heart-disease
#13
Mónica Muñoz-López, Aparna Hoskote, Martin J Chadwick, Anna M Dzieciol, David G Gadian, Kling Chong, Tina Banks, Michelle de Haan, Torsten Baldeweg, Mortimer Mishkin, Faraneh Vargha-Khadem
Neonatal hypoxia can lead to hippocampal atrophy, which can lead, in turn, to memory impairment. To test the generalisability of this causal sequence, we examined a cohort of 41 children aged 8-16, who, having received the arterial switch operation to correct for transposition of the great arteries, had sustained significant neonatal cyanosis but were otherwise neurodevelopmentally normal. As predicted, the cohort had significant bilateral reduction of hippocampal volumes relative to the volumes of 64 normal controls...
December 29, 2016: Hippocampus
https://www.readbyqxmd.com/read/27997999/behavior-dependent-activity-patterns-of-gabaergic-long-range-projecting-neurons-in-the-rat-hippocampus
#14
Linda Katona, Ben Micklem, Zsolt Borhegyi, Daniel A Swiejkowski, Ornella Valenti, Tim J Viney, Dimitrios Kotzadimitriou, Thomas Klausberger, Peter Somogyi
Long-range glutamatergic and GABAergic projections participate in temporal coordination of neuronal activity in distributed cortical areas. In the hippocampus, GABAergic neurons project to the medial septum and retrohippocampal areas. Many GABAergic projection cells express somatostatin (SOM+) and, together with locally terminating SOM+ bistratified and O-LM cells, contribute to dendritic inhibition of pyramidal cells. We tested the hypothesis that diversity in SOM+ cells reflects temporal specialization during behavior using extracellular single cell recording and juxtacellular neurobiotin-labeling in freely moving rats...
December 20, 2016: Hippocampus
https://www.readbyqxmd.com/read/27997994/deciding-what-is-possible-and-impossible-following-hippocampal-damage-in-humans
#15
Cornelia McCormick, Clive R Rosenthal, Thomas D Miller, Eleanor A Maguire
There is currently much debate about whether the precise role of the hippocampus in scene processing is predominantly constructive, perceptual, or mnemonic. Here, we developed a novel experimental paradigm designed to control for general perceptual and mnemonic demands, thus enabling us to specifically vary the requirement for constructive processing. We tested the ability of patients with selective bilateral hippocampal damage and matched control participants to detect either semantic (e.g., an elephant with butterflies for ears) or constructive (e...
December 20, 2016: Hippocampus
https://www.readbyqxmd.com/read/27997993/longitudinal-imaging-reveals-sub-hippocampal-dynamics-in-glutamate-levels-associated-with-histopathologic-events-in-a-mouse-model-of-tauopathy-and-healthy-mice
#16
Rachelle Crescenzi, Catherine DeBrosse, Ravi P R Nanga, Matthew D Byrne, Guruprasad Krishnamoorthy, Kevin D'Aquilla, Hari Nath, Knashawn H Morales, Michiyo Iba, Hari Hariharan, Virginia M Y- Lee, John A Detre, Ravinder Reddy
Tauopathies are neurodegenerative disorders characterized by abnormal intracellular aggregates of tau protein, and include Alzheimer's disease, corticobasal degeneration, frontotemporal dementia, and traumatic brain injury. Glutamate metabolism is altered in neurodegenerative disorders manifesting in higher or lower concentrations of glutamate, its transporters or receptors. Previously, glutamate chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI) demonstrated that glutamate levels are reduced in regions of synapse loss in the hippocampus of a mouse model of late-stage tauopathy...
December 20, 2016: Hippocampus
https://www.readbyqxmd.com/read/27997992/acute-moderate-exercise-improves-mnemonic-discrimination-in-young-adults
#17
Kazuya Suwabe, Kazuki Hyodo, Kyeongho Byun, Genta Ochi, Michael A Yassa, Hideaki Soya
Increasing evidence suggests that regular moderate exercise increases neurogenesis in the dentate gyrus (DG) of the hippocampus and improves memory functions in both humans and animals. The DG is known to play a role in pattern separation, which is the ability to discriminate among similar experiences, a fundamental component of episodic memory. While long-term voluntary exercise improves pattern separation, there is little evidence of alterations in DG function after an acute exercise session. Our previous studies showing acute moderate exercise-enhanced DG activation in rats, and acute moderate exercise-enhanced prefrontal activation and executive function in humans, led us to postulate that acute moderate exercise may also activate the hippocampus, including more specifically the DG, thus improving pattern separation...
December 20, 2016: Hippocampus
https://www.readbyqxmd.com/read/27935155/the-hippocampus-influences-assimilation-and-accommodation-of-schemata-that-are-not-hippocampus-dependent
#18
Anna Armelin, Uwe Heinemann, Livia de Hoz
Learning is facilitated when information can be incorporated into an already learned set of rules or 'mental schema'. The location of a new restaurant, for example, is learned more easily if the neighborhood's general layout is already known. This type of information is processed by the hippocampus and stored as a schema in the cortex, but it is not known whether the hippocampus can also map new stimuli to cortical schemata that are hippocampus-independent, such as odour classification. Using a hippocampus-independent odour-rule task we found that animals without a functional hippocampus learnt which odours did not fit the rule faster than sham animals, which persistently applied the rule to all odours...
December 9, 2016: Hippocampus
https://www.readbyqxmd.com/read/27935149/the-sorting-receptor-sorcs3-is-a-stronger-regulator-of-glutamate-receptor-functions-compared-to-gabaergic-mechanisms-in-the-hippocampus
#19
Gitte B Christiansen, Katrine Andersen, Sarah Riis, Anders Nykjaer, Ulrik Bølcho, Morten Skovgaard Jensen, Mai Marie Holm
Correct function of glutamate receptors in the postsynaptic density is crucial to synaptic function and plasticity. SorCS3 (sortilin-related receptor CNS expressed 3) is a sorting receptor which previously has been shown to interact with the key postsynaptic proteins; PSD-95 and PICK1. In this study, we employed electrophysiological analyses of acute brain slices combined with immunohistochemistry to define the role of SorCS3 in hippocampal synapses in CA1 and the dentate gyrus. We analyzed a juvenile (P17-21) and a young adult (P55-65) group of animals from a Sorcs3 knockout mouse model...
December 9, 2016: Hippocampus
https://www.readbyqxmd.com/read/27933676/white-matter-hyperintensities-are-associated-with-disproportionate-progressive-hippocampal-atrophy
#20
Cassidy M Fiford, Emily N Manning, Jonathan W Bartlett, David M Cash, Ian B Malone, Gerard R Ridgway, Manja Lehmann, Kelvin K Leung, Carole Sudre, Sebastien Ourselin, Geert Jan Biessels, Owen T Carmichael, Nick C Fox, M Jorge Cardoso, Josephine Barnes
This study investigates relationships between white matter hyperintensity (WMH) volume, cerebrospinal fluid (CSF) Alzheimer's disease (AD) pathology markers, and brain and hippocampal volume loss. Subjects included 198 controls, 345 Mild Cognitive Impairment (MCI) and 154 AD subjects with serial volumetric 1.5T MRI. CSF Aβ42 and total tau were measured (n=353). Brain and hippocampal loss were quantified from serial MRI using the Boundary Shift Integral (BSI). Multiple linear regression models assessed the relationships between WMHs and hippocampal and brain atrophy rates...
December 9, 2016: Hippocampus
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