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https://www.readbyqxmd.com/read/28434800/medial-entorhinal-cortex-selectively-supports-temporal-coding-by-hippocampal-neurons
#1
Nick T M Robinson, James B Priestley, Jon W Rueckemann, Aaron D Garcia, Vittoria A Smeglin, Francesca A Marino, Howard Eichenbaum
Recent studies have shown that hippocampal "time cells" code for sequential moments in temporally organized experiences. However, it is currently unknown whether these temporal firing patterns critically rely on upstream cortical input. Here we employ an optogenetic approach to explore the effect of large-scale inactivation of the medial entorhinal cortex on temporal, as well as spatial and object, coding by hippocampal CA1 neurons. Medial entorhinal inactivation produced a specific deficit in temporal coding in CA1 and resulted in significant impairment in memory across a temporal delay...
April 13, 2017: Neuron
https://www.readbyqxmd.com/read/28433653/self-awareness-and-the-medial-temporal-lobe-in-neurodegenerative-diseases
#2
REVIEW
Chantal Chavoix, Ricardo Insausti
Accurate self-awareness is essential for adapting one's behaviour to one's actual abilities, to avoid risky behaviour. Impaired self-awareness of deficits is common in neurodegenerative diseases. Numerous studies show an involvement of midline cortical areas in impaired self-awareness. Among the other brain regions implicated stand the medial temporal lobe (MTL) structures (i.e. hippocampus, amygdala, and temporopolar, entorhinal, perirhinal and posterior parahippocampal cortices). This review aims at evaluating the role of those structures in self-awareness in neurodegenerative diseases...
April 19, 2017: Neuroscience and Biobehavioral Reviews
https://www.readbyqxmd.com/read/28431164/low-activity-microstates-during-sleep
#3
Hiroyuki Miyawaki, Yazan N Billeh, Kamran Diba
Study Objectives: To better understand the distinct activity patterns of the brain during sleep, we observed and investigated periods of diminished oscillatory and population spiking activity lasting for seconds during non-REM sleep, which we call "LOW" activity sleep. Methods: We analyzed spiking and local field potential (LFP) activity of hippocampal CA1 region alongside neocortical electroencephalogram (EEG) and electromyogram (EMG) in 19 sessions from four male Long-Evans rats (262-363g) during natural wake/sleep across the 24-hr cycle, as well as data from other brain regions obtained from http://crcns...
April 18, 2017: Sleep
https://www.readbyqxmd.com/read/28426128/hippocampal-electrical-stimulation-disrupts-associative-learning-when-targeted-at-dentate-spikes
#4
Miriam S Nokia, Irina Gureviciene, Tomi Waselius, Heikki Tanila, Markku Penttonen
Hippocampal electrophysiological oscillations, namely theta and ripples, have been implicated in encoding and consolidation of new memories, respectively. According to existing literature, hippocampal dentate spikes are prominent, short-duration (<30 ms), large-amplitude (∼2-4 mV) fluctuations in hilar local-field potentials that take place during awake immobility and sleep. Interestingly, previous studies indicate that during dentate spikes dentate gyrus granule cells increase their firing while firing of CA1 pyramidal cells are suppressed, thus resulting in momentary uncoupling of the two hippocampal subregions...
April 20, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28425185/the-influence-of-hippocampal-atrophy-on-the-cognitive-phenotype-of-dementia-with-lewy-bodies
#5
Greg J Elder, Karen Mactier, Sean J Colloby, Rosie Watson, Andrew M Blamire, John T O'Brien, John-Paul Taylor
OBJECTIVE: The level of hippocampal atrophy in dementia with Lewy bodies (DLB) is typically less than that observed in Alzheimer's disease (AD). However, it is not known how the cognitive phenotype of DLB is influenced by hippocampal atrophy or the atrophy of adjacent medial temporal lobe structures. METHODS: Dementia with Lewy bodies (n = 65), AD (n = 76) and control (n = 63) participants underwent 3T magnetic resonance imaging and cognitive Cambridge Cognitive Examination and Mini-Mental State Examination (CAMCOG and MMSE) assessments...
April 20, 2017: International Journal of Geriatric Psychiatry
https://www.readbyqxmd.com/read/28424398/-brodmann-areas-27-28-36-and-37-the-parahippocampal-and-the-fusiform-gyri
#6
Satoshi Eifuku
First, Brodmann areas 27, 28, 36 and 37, were anatomically defined in the beginning of this review. These areas exist in the parahippocampal or fusiform gyrus of the ventral temporal lobe in humans. Subsequently, the current understanding of their functions was summarized on the basis of recent findings mainly through human functional neuroimaging studies and animal studies. Rodent studies have shown the existence of neuronal activities for representing space, such as those involving head-direction cells or grid cells, in areas 27 (the parasubicular cortex) and 28 (the ventral entorhinal cortex)...
April 2017: Brain and Nerve, Shinkei Kenkyū No Shinpo
https://www.readbyqxmd.com/read/28424397/-spatial-cognition-and-episodic-memory-formation-in-the-limbic-cortex
#7
Yasushi Kobayashi
The limbic lobe defined by Broca is a cortical region with highly diverse structure and functions, and comprises the paleo-, archi-, and neocortices as well as their transitional zones. In the limbic lobe, Brodmann designated areas 27, 28, 34, 35, and 36 adjacent to the hippocampus, and areas 23, 24, 25, 26, 29, 30, 31, 32, and 33 around the corpus callosum. In the current literature, areas 27 and 28 correspond to the presubiculum and entorhinal cortex, respectively. Area 34 represents the cortico-medial part of the amygdaloid complex...
April 2017: Brain and Nerve, Shinkei Kenkyū No Shinpo
https://www.readbyqxmd.com/read/28422371/effects-of-m1-and-m4-activation-on-excitatory-synaptic-transmission-in-ca1
#8
Catherine Thorn, Michael Popiolek, Eda Stark, Jeremy Edgerton
Hippocampal networks are particularly susceptible to dysfunction in many neurodegenerative diseases and neuropsychiatric disorders including Alzheimer's disease, Lewy body dementia, and schizophrenia. CA1, a major output region of the hippocampus, receives glutamatergic input from both hippocampal CA3 and entorhinal cortex, via the Schaffer collateral (SC) and temporoammonic (TA) pathways, respectively. SC and TA inputs to CA1 are thought to be differentially involved in the retrieval of previously stored memories versus the encoding of novel information, and switching between these two crucial hippocampal functions is thought to critically depend on acetylcholine (ACh) acting at muscarinic receptors...
April 19, 2017: Hippocampus
https://www.readbyqxmd.com/read/28416442/allopregnanolone-decreases-interictal-spiking-and-fast-ripples-in-an-animal-model-of-mesial-temporal-lobe-epilepsy
#9
Maxime Lévesque, Rochelle Herrington, Leila Leclerc, Michael A Rogawski, Massimo Avoli
The objective of this study was to characterize the impact of allopregnanolone, a neurosteroid that acts as a positive allosteric modulator of synaptic and extrasynaptic GABAA receptors, on interictal spikes and high-frequency oscillations (ripples: 80-200 Hz, fast ripples: 250-500 Hz) in the pilocarpine model of mesial temporal lobe epilepsy. Seven out of 25 Sprague-Dawley rats experiencing 1 h of pilocarpine-induced status epilepticus (SE) began treatment with allopregnanolone (9.6-12.8 mg/kg/day) on the following day...
April 14, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28396399/context-dependent-spatially-periodic-activity-in-the-human-entorhinal-cortex
#10
Zoltan Nadasdy, T Peter Nguyen, Ágoston Török, Jason Y Shen, Deborah E Briggs, Pradeep N Modur, Robert J Buchanan
The spatially periodic activity of grid cells in the entorhinal cortex (EC) of the rodent, primate, and human provides a coordinate system that, together with the hippocampus, informs an individual of its location relative to the environment and encodes the memory of that location. Among the most defining features of grid-cell activity are the 60° rotational symmetry of grids and preservation of grid scale across environments. Grid cells, however, do display a limited degree of adaptation to environments. It remains unclear if this level of environment invariance generalizes to human grid-cell analogs, where the relative contribution of visual input to the multimodal sensory input of the EC is significantly larger than in rodents...
April 10, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28392071/a-multiplexed-heterogeneous-and-adaptive-code-for-navigation-in-medial-entorhinal-cortex
#11
Kiah Hardcastle, Niru Maheswaranathan, Surya Ganguli, Lisa M Giocomo
Medial entorhinal grid cells display strikingly symmetric spatial firing patterns. The clarity of these patterns motivated the use of specific activity pattern shapes to classify entorhinal cell types. While this approach successfully revealed cells that encode boundaries, head direction, and running speed, it left a majority of cells unclassified, and its pre-defined nature may have missed unconventional, yet important coding properties. Here, we apply an unbiased statistical approach to search for cells that encode navigationally relevant variables...
April 19, 2017: Neuron
https://www.readbyqxmd.com/read/28391402/distinct-gamma-oscillations-in-the-distal-dendritic-fields-of-the-dentate-gyrus-and-the-ca1-area-of-mouse-hippocampus
#12
Bálint Lasztóczi, Thomas Klausberger
The molecular layer of the dentate gyrus and the anatomically adjacent stratum lacunosum-moleculare of CA1 area, represent afferent areas at distinct levels of the hippocampal trisynaptic loop. Afferents to the dentate gyrus and CA1 area originate from different cell populations, including projection cells in entorhinal cortex layers two and three, respectively. To determine the organization of oscillatory activities along these terminal fields, we recorded local field potentials from multiple sites in the dentate gyrus and CA1 area of the awake mice, and localized gamma frequency (30-150 Hz) oscillations in different layers by means of current source density analysis...
April 8, 2017: Brain Structure & Function
https://www.readbyqxmd.com/read/28387676/identification-of-fungal-species-in-brain-tissue-from-alzheimer-s-disease-by-next-generation-sequencing
#13
Ruth Alonso, Diana Pisa, Begoña Aguado, Luis Carrasco
The possibility that patients diagnosed with Alzheimer's disease (AD) have disseminated fungal infection has been recently advanced by the demonstration of fungal proteins and DNA in nervous tissue from AD patients. In the present study, next-generation sequencing (NGS) was used to identify fungal species present in the central nervous system (CNS) of AD patients. Initially, DNA was extracted from frozen tissue from four different CNS regions of one AD patient and the fungi in each region were identified by NGS...
April 3, 2017: Journal of Alzheimer's Disease: JAD
https://www.readbyqxmd.com/read/28386011/engrams-and-circuits-crucial-for-systems-consolidation-of-a-memory
#14
Takashi Kitamura, Sachie K Ogawa, Dheeraj S Roy, Teruhiro Okuyama, Mark D Morrissey, Lillian M Smith, Roger L Redondo, Susumu Tonegawa
Episodic memories initially require rapid synaptic plasticity within the hippocampus for their formation and are gradually consolidated in neocortical networks for permanent storage. However, the engrams and circuits that support neocortical memory consolidation have thus far been unknown. We found that neocortical prefrontal memory engram cells, which are critical for remote contextual fear memory, were rapidly generated during initial learning through inputs from both the hippocampal-entorhinal cortex network and the basolateral amygdala...
April 7, 2017: Science
https://www.readbyqxmd.com/read/28385633/impaired-expression-of-gaba-transporters-in-the-human-alzheimer-s-disease-hippocampus-subiculum-entorhinal-cortex-and-superior-temporal-gyrus
#15
Tessa E Fuhrer, Thulani H Palpagama, Henry J Waldvogel, Beth J L Synek, Clinton Turner, Richard L Faull, Andrea Kwakowsky
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain and plays an important role in regulating neuronal excitability. GABA reuptake from the synapse is dependent on specific transporters - mainly GAT-1, GAT-3 and BGT-1 (GATs). This study is the first to show alterations in the expression of the GATs in the Alzheimer's disease (AD) hippocampus, entorhinal cortex and superior temporal gyrus. We found a significant increase in BGT-1 expression associated with AD in all layers of the dentate gyrus, in the stratum oriens of the CA2 and CA3 and the superior temporal gyrus...
April 4, 2017: Neuroscience
https://www.readbyqxmd.com/read/28378878/network-evolution-in-mesial-temporal-lobe-epilepsy-revealed-by-diffusion-tensor-imaging
#16
Helen Wang, Yuegao Huang, Daniel Coman, Reshma Munbodh, Roni Dhaher, Hitten P Zaveri, Fahmeed Hyder, Tore Eid
OBJECTIVE: The objective of the present study is to identify novel, time-indexed imaging biomarkers of epileptogenesis in mesial temporal lobe epilepsy (MTLE). METHODS: We used high-resolution brain diffusion tensor imaging (DTI) of the translationally relevant methionine sulfoximine (MSO) brain infusion model of MTLE. MSO inhibits astroglial glutamine synthetase, which is deficient in the epileptogenic hippocampal formation of patients with MTLE. MSO-infused (epileptogenic) rats were compared with phosphate-buffered saline (PBS)-infused (nonepileptogenic) rats at early (3-4 days) and late (6-9 weeks) time points during epileptogenesis...
April 5, 2017: Epilepsia
https://www.readbyqxmd.com/read/28375615/specific-connectivity-and-unique-molecular-identity-of-met-receptor-tyrosine-kinase-expressing-serotonergic-neurons-in-the-caudal-dorsal-raphe-nuclei
#17
Ryan J Kast, Hsiao-Huei Wu, Piper Williams, Patricia Gaspar, Pat Levitt
Molecular characterization of neurons across brain regions has revealed new taxonomies for understanding functional diversity even among classically defined neuronal populations. Neuronal diversity has become evident within the brain serotonin (5-HT) system, which is far more complex than previously appreciated. However, until now it has been difficult to define subpopulations of 5-HT neurons based on molecular phenotypes. We demonstrate that the MET receptor tyrosine kinase (MET) is specifically expressed in a subset of 5-HT neurons within the caudal part of the dorsal raphe nuclei (DRC) that is encompassed by the classic B6 serotonin cell group...
April 4, 2017: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/28368242/somatostatin-positive-interneurons-in-the-dentate-gyrus-of-mice-provide-local-and-long-range-septal-synaptic-inhibition
#18
Mei Yuan, Thomas Meyer, Christoph Benkowitz, Shakuntala Savanthrapadian, Laura Ansel-Bollepalli, Angelica Foggetti, Peer Wulff, Pepe Alcami, Claudio Elgueta, Marlene Bartos
Somatostatin-expressing-interneurons (SOMIs) in the dentate gyrus (DG) control formation of granule cell (GC) assemblies during memory acquisition. Hilar-perforant-path-associated interneurons (HIPP cells) have been considered to be synonymous for DG-SOMIs. Deviating from this assumption, we show two functionally contrasting DG-SOMI-types. The classical feedback-inhibitory HIPPs distribute axon fibers in the molecular layer. They are engaged by converging GC-inputs and provide dendritic inhibition to the DG circuitry...
April 3, 2017: ELife
https://www.readbyqxmd.com/read/28365375/preclinical-molecular-imaging-of-glutamatergic-and-dopaminergic-neuroreceptor-kinetics-in-obsessive-compulsive-disorder
#19
S Servaes, D Glorie, J Verhaeghe, S Stroobants, S Staelens
BACKGROUND: Molecular neuroimaging was applied in the quinpirole rat model for compulsive checking in OCD to visualize the D2- and mGluR5-receptor occupancy with Raclopride and ABP-688 microPET/CT. METHODS: Animals (n=48) were exposed to either saline (CTRL; 1mL/kg) or quinpirole (QP; dopamine D2-agonist, 0.5mg/kg) in a single injection (RAC and ABP acute groups) or twice-weekly during 7weeks (chronic group). Animals underwent PET/CT after the 1st injection (acute) or before initial exposure and following the 10th injection in week 5 (chronic)...
March 30, 2017: Progress in Neuro-psychopharmacology & Biological Psychiatry
https://www.readbyqxmd.com/read/28359883/the-bdnf-val-66-met-polymorphism-is-associated-with-structural-neuroanatomical-differences-in-young-children
#20
Kaja K Jasińska, Peter J Molfese, Sergey A Kornilov, W Einar Mencl, Stephen J Frost, Maria Lee, Kenneth R Pugh, Elena L Grigorenko, Nicole Landi
The brain-derived neurotrophic factor (BDNF) Val(66)Met single nucleotide polymorphism (SNP) has been associated with individual differences in brain structure and function, and cognition. Research on BDNF's influence on brain and cognition has largely been limited to adults, and little is known about the association of this gene, and specifically the Val(66)Met polymorphism, with developing brain structure and emerging cognitive functions in children. We performed a targeted genetic association analysis on cortical thickness, surface area, and subcortical volume in 78 children (ages 6-10) who were Val homozygotes (homozygous Val/Val carriers) or Met carriers (Val/Met, Met/Met) for the Val(66)Met locus using Atlas-based brain segmentation...
March 27, 2017: Behavioural Brain Research
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