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Hippocampus

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https://www.readbyqxmd.com/read/28710800/dissociation-of-spatial-memory-systems-in-williams-syndrome
#1
Mathilde Bostelmann, Emilie Fragnière, Floriana Costanzo, Silvia Di Vara, Deny Menghini, Stefano Vicari, Pierre Lavenex, Pamela Banta Lavenex
Williams syndrome (WS), a genetic deletion syndrome, is characterized by severe visuospatial deficits affecting performance on both tabletop spatial tasks and on tasks which assess orientation and navigation. Nevertheless, previous studies of WS spatial capacities have ignored the fact that two different spatial memory systems are believed to contribute parallel spatial representations supporting navigation. The place learning system depends on the hippocampal formation and creates flexible relational representations of the environment, also known as cognitive maps...
July 15, 2017: Hippocampus
https://www.readbyqxmd.com/read/28696588/feedforward-inhibition-is-randomly-wired-from-individual-granule-cells-onto-ca3-pyramidal-cells
#2
Máté Neubrandt, Viktor János Oláh, János Brunner, János Szabadics
Feedforward inhibition (FFI) between the dentate gyrus (DG) and CA3 sparsifies and shapes memory- and spatial navigation-related activities. However, our understanding of this prototypical FFI circuit lacks essential details, as the wiring of FFI is not yet mapped between individual DG granule cells (GCs) and CA3 pyramidal cells (PCs). Importantly, theoretically opposite network contributions are possible depending on whether the directly excited PCs are differently inhibited than the non-excited PCs. Therefore, to better understand FFI wiring schemes, we compared the prevalence of disynaptic inhibitory postsynaptic events (diIPSCs) between pairs of individually recorded GC axons or somas and PCs, some of which were connected by monosynaptic excitation, while others were not...
July 11, 2017: Hippocampus
https://www.readbyqxmd.com/read/28686814/early-survival-and-delayed-death-of-developmentally-born-dentate-gyrus-neurons
#3
Shaina P Cahill, Ru Qi Yu, Dylan Green, Evgenia V Todorova, Jason S Snyder
The storage and persistence of memories depends on plasticity in the hippocampus. Adult neurogenesis produces new neurons that mature through critical periods for plasticity and cellular survival, which determine their contributions to learning and memory. However, most granule neurons are generated prior to adulthood; the maturational timecourse of these neurons is poorly understood compared to adult-born neurons, but is essential to identify how the dentate gyrus, as a whole, contributes to behavior. To characterize neurons born in the early postnatal period, we labeled dentate gyrus neurons born on postnatal day 6 (P6) with BrdU and quantified maturation and survival across early (1 hour to 8 weeks old) and late (2-6 months old) cell ages...
July 7, 2017: Hippocampus
https://www.readbyqxmd.com/read/28686806/hippocampal-damage-causes-retrograde-but-not-anterograde-memory-loss-for-context-fear-discrimination-in-rats
#4
Justin Q Lee, Robert J Sutherland, Robert J McDonald
There is a substantial body of evidence that the hippocampus (HPC) plays and essential role in context discrimination in rodents. Studies reporting anterograde amnesia (AA) used repeated, alternating, distributed conditioning and extinction sessions to measure context fear discrimination. In addition, there is uncertainty about the extent of damage to the HPC. Here, we induced conditioned fear prior to discrimination tests and rats sustained extensive, quantified pre- or post-training HPC damage. Unlike previous work, we found that extensive HPC damage spares context discrimination, we observed no AA...
July 7, 2017: Hippocampus
https://www.readbyqxmd.com/read/28686803/the-calcium-sensor-synaptotagmin-1-is-expressed-and-regulated-in-hippocampal-postsynaptic-spines
#5
Suleman Hussain, Daniel Lawer Egbenya, Yi-Chen Lai, Zita J Dosa, Jakob B Sørensen, Anne Anderson, Svend Davanger
Synaptotagmin 1 is a presynaptic calcium sensor, regulating SNARE-mediated vesicle exocytosis of transmitter. Increasing evidence indicate roles of SNARE proteins in postsynaptic glutamate receptor trafficking. However, a possible postsynaptic expression of synaptotagmin 1 has not been demonstrated previously. Here, we used postembedding immunogold electron microscopy to determine the subsynaptic localization of synaptotagmin 1 in rat hippocampal CA1 Schaffer collateral synapses. We report for the first time that synaptotagmin 1 is present in rat hippocampal postsynaptic spines, both on cytoplasmic vesicles and at the postsynaptic density (PSD)...
July 7, 2017: Hippocampus
https://www.readbyqxmd.com/read/28686801/exposure-to-complex-environments-results-in-more-sparse-representations-of-space-in-the-hippocampus
#6
David K Bilkey, Kirsten R Cheyne, Michael J Eckert, Xiaodong Lu, Shoaib Chowdhury, Paul F Worley, James E Crandall, Wickliffe C Abraham
The neural circuitry mediating sensory and motor representations is adaptively tuned by an animal's interaction with its environment. Similarly, higher order representations such as spatial memories can be modified by exposure to a complex environment (CE), but in this case the changes in brain circuitry that mediate the effect are less well understood. Here we show that prolonged CE exposure was associated with increased selectivity of CA1 "place cells" to a particular recording arena compared to a social control (SC) group...
July 7, 2017: Hippocampus
https://www.readbyqxmd.com/read/28667703/hippocampal-gamma-slow-oscillation-coupling-in-macaques-during-sedation-and-sleep
#7
Andrew G Richardson, Xilin Liu, Pauline K Weigand, Eric D Hudgins, Joel M Stein, Sandhitsu R Das, Alexander Proekt, Max B Kelz, Milin Zhang, Jan Van der Spiegel, Timothy H Lucas
Behavioral and neurophysiological evidence suggests that the slow (≤ 1 Hz) oscillation (SO) during sleep plays a role in consolidating hippocampal (HIPP)-dependent memories. The effects of the SO on HIPP activity have been studied in rodents and cats both during natural sleep and during anesthetic administration titrated to mimic sleep-like slow rhythms. In this study, we sought to document these effects in primates. First, HIPP field potentials were recorded during ketamine-dexmedetomidine sedation and during natural sleep in three rhesus macaques...
July 1, 2017: Hippocampus
https://www.readbyqxmd.com/read/28667695/recognition-memory-cellular-evidence-of-a-massive-contribution-of-the-lec-to-familiarity-and-a-lack-of-involvement-of-the-hippocampal-subfields-ca1-and-ca3
#8
Erika Atucha, Artem Karew, Takashi Kitsukawa, Magdalena M Sauvage
A highly debated issue in memory research is whether familiarity is supported by the parahippocampal region, especially the lateral (LEC) and the perirhinal (PER) cortices, or whether it is supported by the same brain structure as recollection: the hippocampus. One reason for this is that conflicting results have emerged regarding the contribution of the hippocampus to familiarity. This might stem from the lack of dissociation between hippocampal subfields CA1 and CA3 as these areas are involved to a different extent in processes which are pertinent to familiarity...
July 1, 2017: Hippocampus
https://www.readbyqxmd.com/read/28667676/cannabinoids-prevent-the-differential-long-term-effects-of-exposure-to-severe-stress-on-hippocampal-and-amygdala-dependent-memory-and-plasticity
#9
Noa Shoshan, Amir Segev, Hila Abush, Tomer Mizrachi Zer-Aviv, Irit Akirav
Exposure to excessive or uncontrolled stress is a major factor associated with various diseases including posttraumatic stress disorder (PTSD). The consequences of exposure to trauma are affected not only by aspects of the event itself, but also by the frequency and severity of trauma reminders. It was suggested that in PTSD, hippocampal-dependent memory is compromised while amygdala-dependent memory is strengthened. Several lines of evidence support the role of the endocannabinoid (eCB) system as a modulator of the stress response...
July 1, 2017: Hippocampus
https://www.readbyqxmd.com/read/28667671/smaller-hippocampal-subfield-volumes-predict-verbal-associative-memory-in-pediatric-brain-tumor-survivors
#10
Alexandra L Decker, Kamila U Szulc, Eric Bouffet, Suzanne Laughlin, M Mallar Chakravarty, Jovanka Skocic, Cynthia B de Medeiros, Donald J Mabbott
The developing hippocampus is highly sensitive to chemotherapy and cranial radiation treatments for pediatric cancers, yet little is known about the effects that cancer treatments have on specific hippocampal subfields. Here, we examined hippocampal subfield volumes in twenty-nine pediatric brain tumor survivors treated with cranial radiation and chemotherapy, and thirty healthy developing children and adolescents. We also examined associations between hippocampal subfield volumes and short-term verbal memory...
July 1, 2017: Hippocampus
https://www.readbyqxmd.com/read/28667669/optogenetic-stimulation-of-dentate-gyrus-engrams-restores-memory-in-alzheimer-s-disease-mice
#11
Jennifer N Perusini, Stephanie A Cajigas, Omid Cohensedgh, Sean C Lim, Ina P Pavlova, Zoe R Donaldson, Christine A Denny
Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by amyloid-beta (Aβ) plaques and tau neurofibrillary tangles. APPswe/PS1dE9 (APP/PS1) mice have been developed as an AD model and are characterized by plaque formation at 4-6 months of age. Here, we sought to better understand AD-related cognitive decline by characterizing various types of memory. In order to better understand how memory declines with AD, APP/PS1 mice were bred with ArcCreER(T2) mice. In this line, neural ensembles activated during memory encoding can be indelibly tagged and directly compared with neural ensembles activated during memory retrieval (i...
July 1, 2017: Hippocampus
https://www.readbyqxmd.com/read/28628945/precise-spike-timing-dynamics-of-hippocampal-place-cell-activity-sensitive-to-cholinergic-disruption
#12
Ehren L Newman, Sarah Jo C Venditto, Jason R Climer, Elijah A Petter, Shea N Gillet, Sam Levy
New memory formation depends upon both the hippocampus and modulatory effects of acetylcholine. The mechanism by which acetylcholine levels in the hippocampus enable new encoding remains poorly understood. Here, we tested the hypothesis that cholinergic modulation supports memory formation by leading to structured spike timing in the hippocampus. Specifically, we tested if phase precession in dorsal CA1 was reduced under the influence of a systemic cholinergic antagonist. Unit and field potential was recorded from the dorsal CA1 of rats as they completed laps on a circular track for food rewards before and during the influence of the systemically administered acetylcholine muscarinic receptor antagonist scopolamine...
June 19, 2017: Hippocampus
https://www.readbyqxmd.com/read/28609014/space-time-and-episodic-memory-the-hippocampus-is-all-over-the-cognitive-map
#13
Arne D Ekstrom, Charan Ranganath
In recent years, the field has reached an impasse between models suggesting that the hippocampus is fundamentally involved in spatial processing and models suggesting that the hippocampus automatically encodes all dimensions of experience in the service of memory. Here, we consider key conceptual issues that have impeded progress in our understanding of hippocampal function, and we review findings that establish the scope and limits of hippocampal involvement in navigation and memory. We argue that space and time serve as a primary scaffold to break up experiences into specific contexts, and to organize multimodal input that is to be associated within a context...
June 13, 2017: Hippocampus
https://www.readbyqxmd.com/read/28608989/seizure-severity-dependent-selective-vulnerability-of-the-granule-cell-layer-and-aberrant-neurogenesis-in-the-rat-hippocampus
#14
Takeshi Uemori, Keiko Toda, Tatsunori Seki
The pilocarpine-induced status epilepticus (SE) rodent model has been commonly used to analyze the mechanisms of human temporal lobe epilepsy. Recent studies using this model have demonstrated that epileptic seizures lead to increased adult neurogenesis of the dentate granule cells, and cause abnormal cellular organization in dentate neuronal circuits. In this study, we examined these structural changes in rats with seizures of varying severity. In rats with frequent severe seizures, we found a clear loss of Prox1 and NeuN expression in the dentate granule cell layer (GCL), which was confined mainly to the suprapyramidal blade of the GCL at the septal and middle regions of the septo-temporal axis of the hippocampus...
June 13, 2017: Hippocampus
https://www.readbyqxmd.com/read/28608960/theta-band-power-increases-in-the-posterior-hippocampus-predict-successful-episodic-memory-encoding-in-humans
#15
Jui-Jui Lin, Michael D Rugg, Sandhitsu Das, Joel Stein, Daniel S Rizzuto, Michael J Kahana, Bradley C Lega
Functional differences in the anterior and posterior hippocampus during episodic memory processing have not been examined in human electrophysiological data. This is in spite of strong evidence for such differences in rodent data, including greater place cell specificity in the dorsal hippocampus, greater sensitivity to the aversive or motivational content of memories in ventral regions, connectivity analyses identifying preferential ventral hippocampal connections with the amygdala, and gene expression analyses identifying a dorsal-ventral gradient...
June 13, 2017: Hippocampus
https://www.readbyqxmd.com/read/28599071/predator-odor-evokes-sex-independent-stress-responses-in-male-and-female-wistar-rats-and-reduces-phosphorylation-of-cyclic-adenosine-monophosphate-response-element-binding-protein-creb-in-the-male-but-not-the-female-hippocampus
#16
Damek Homiack, Emma O'Cinneide, Sema Hajmurad, Brett Barrileaux, Mary Stanley, Michael R Kreutz, Laura Schrader
Post-traumatic stress disorder (PTSD) is characterized by memory disturbances following trauma. Acute predator threat has emerged as an ethological model of PTSD, yet the effects of predator odor on signaling cascades associated with long-term memory remain poorly understood. In this study, we exposed male and female Wistar rats to the synthetic predator odor 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) to assess behavioral and physiological responses as well as rapid modulation of signal transduction cascades associated with learning and memory in the male and female hippocampus...
June 9, 2017: Hippocampus
https://www.readbyqxmd.com/read/28653801/a-putative-lysophosphatidylinositol-receptor-gpr55-modulates-hippocampal-synaptic-plasticity
#17
Katrina Hurst, Corinne Badgley, Tanner Ellsworth, Spencer Bell, Lindsey Friend, Brad Prince, Jacob Welch, Zack Cowan, Ryan Williamson, Chris Lyon, Brandon Anderson, Brian Poole, Michael Christensen, Michael McNeil, Jarrod Call, Jeffrey G Edwards
GPR55, an orphan G-protein coupled receptor, is activated by lysophosphatidylinositol (LPI) and the endocannabinoid anandamide, as well as by other compounds including THC. LPI is a potent endogenous ligand of GPR55 and neither GPR55 nor LPIs' functions in the brain are well understood. While endocannabinoids are well known to modulate brain synaptic plasticity, the potential role LPI could have on brain plasticity has never been demonstrated. Therefore, we examined not only GPR55 expression, but also the role its endogenous ligand could play in long-term potentiation, a common form of synaptic plasticity...
June 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28597498/different-implications-of-the-dorsal-and-ventral-hippocampus-on-contextual-memory-retrieval-after-stress
#18
C Pierard, R Dorey, N Henkous, N Mons, D Béracochéa
This study assessed the relative contributions of dorsal (dHPC) and ventral (vHPC) hippocampus regions in mediating the rapid effects of an acute stress on contextual memory retrieval. Indeed, we previously showed that an acute stress (3 electric footschocks; 0.9 mA each) delivered 15 min before the 24h-test inversed the memory retrieval pattern in a contextual discrimination task. Specifically, mice learned in a four-hole board two successive discriminations (D1 and D2) varying by the color and texture of the floor...
June 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28597491/hippocampal-neurogenesis-and-pattern-separation-a-meta-analysis-of-behavioral-data
#19
Thiago F A França, Alexandre M Bitencourt, Naiana R Maximilla, Daniela M Barros, José M Monserrat
The generation of new neurons in the hippocampus of adult mammals has become a widely accepted phenomenon, but the functional significance of the adult neurogenesis in the hippocampus is not fully understood. One of the main hypotheses currently investigated suggests that neurogenesis contributes to pattern separation in the dentate gyrus. Many behavioral studies were conducted aiming to test this hypothesis using rodents as animal model. In those studies, researches ablated neurogenesis in the animals and subsequently evaluate them in tests of behavioral pattern separation, that is, behaviors that are thought to rely on the computational process of pattern separation...
June 8, 2017: Hippocampus
https://www.readbyqxmd.com/read/28558154/theta-paced-flickering-between-place-cell-maps-in-the-hippocampus-a-model-based-on-short-term-synaptic-plasticity
#20
Shirley Mark, Sandro Romani, Karel Jezek, Misha Tsodyks
Hippocampal place cells represent different environments with distinct neural activity patterns. Following an abrupt switch between two familiar configurations of visual cues defining two environments, the hippocampal neural activity pattern switches almost immediately to the corresponding representation. Surprisingly, during a transient period following the switch to the new environment, occasional fast transitions of activity patterns between the representations (flickering) were observed (Jezek et al. 2011)...
May 30, 2017: Hippocampus
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