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Pattern completion and hippocampus

Sean C Piantadosi, Beverly J French, Michael M Poe, Tamara Timić, Bojan D Marković, Mohan Pabba, Marianne L Seney, Hyunjung Oh, Beverley A Orser, Miroslav M Savić, James M Cook, Etienne Sibille
Rationale: Current first-line treatments for stress-related disorders such as major depressive disorder (MDD) act on monoaminergic systems and take weeks to achieve a therapeutic effect with poor response and low remission rates. Recent research has implicated the GABAergic system in the pathophysiology of depression, including deficits in interneurons targeting the dendritic compartment of cortical pyramidal cells. Objectives: The present study evaluates whether SH-053-2'F-R-CH3 (denoted "α5-PAM"), a positive allosteric modulator selective for α5-subunit containing GABAA receptors found predominantly on cortical pyramidal cell dendrites, has anti-stress effects...
2016: Frontiers in Pharmacology
Emily C Edmonds, Katherine J Bangen, Lisa Delano-Wood, Daniel A Nation, Ansgar J Furst, David P Salmon, Mark W Bondi
OBJECTIVES: We examined florbetapir positron emission tomography (PET) amyloid scans across stages of preclinical Alzheimer's disease (AD) in cortical, allocortical, and subcortical regions. Stages were characterized using empirically defined methods. METHODS: A total of 312 cognitively normal Alzheimer's Disease Neuroimaging Initiative participants completed a neuropsychological assessment and florbetapir PET scan. Participants were classified into stages of preclinical AD using (1) a novel approach based on the number of abnormal biomarkers/cognitive markers each individual possessed, and (2) National Institute on Aging and the Alzheimer's Association (NIA-AA) criteria...
November 2016: Journal of the International Neuropsychological Society: JINS
Christopher L Rees, Diek W Wheeler, David J Hamilton, Charise M White, Alexander O Komendantov, Giorgio A Ascoli
We computed the potential connectivity map of all known neuron types in the rodent hippocampal formation by supplementing scantly available synaptic data with spatial distributions of axons and dendrites from the open-access knowledge base The network that results from this endeavor, the broadest and most complete for a mammalian cortical region at the neuron-type level to date, contains more than 3200 connections among 122 neuron types across six subregions. Analyses of these data using graph theory metrics unveil the fundamental architectural principles of the hippocampal circuit...
November 2016: ENeuro
Dominik Fröhlich, Alexandra K Suchowerska, Ziggy H T Spencer, Georg von Jonquieres, Claudia B Klugmann, Andre Bongers, Fabien Delerue, Holly Stefen, Lars M Ittner, Thomas Fath, Gary D Housley, Matthias Klugmann
BACKGROUND: The recently diagnosed leukodystrophy Hypomyelination with Brain stem and Spinal cord involvement and Leg spasticity (HBSL) is caused by mutations of the cytoplasmic aspartyl-tRNA synthetase geneDARS. The physiological role of DARS in translation is to accurately pair aspartate with its cognate tRNA. Clinically, HBSL subjects show a distinct pattern of hypomyelination and develop progressive leg spasticity, variable cognitive impairment and epilepsy. To elucidate the underlying pathomechanism, we comprehensively assessed endogenous DARS expression in mice...
November 2, 2016: Neurobiology of Disease
Shih-Dar Chang, K C Liang
Contextual fear conditioning involves forming a representation for the context and associating it with a shock, which were attributed by the prevailing view to functions of the hippocampus and amygdala respectively. Yet our recent evidence suggested that both processes require integrity of the dorsal hippocampus (DH). In view of the DH involvement in uniting multiple stimuli into a configuration, this study examined whether the DH would integrate context and shock into a shocked-context representation. Male Wistar rats were trained on a two-phase training paradigm of contextual fear conditioning...
November 2, 2016: Hippocampus
A P Allen, W Hutch, Y E Borre, P J Kennedy, A Temko, G Boylan, E Murphy, J F Cryan, T G Dinan, G Clarke
The emerging concept of psychobiotics-live microorganisms with a potential mental health benefit-represents a novel approach for the management of stress-related conditions. The majority of studies have focused on animal models. Recent preclinical studies have identified the B. longum 1714 strain as a putative psychobiotic with an impact on stress-related behaviors, physiology and cognitive performance. Whether such preclinical effects could be translated to healthy human volunteers remains unknown. We tested whether psychobiotic consumption could affect the stress response, cognition and brain activity patterns...
November 1, 2016: Translational Psychiatry
Stevenson Baker, Paula Vieweg, Fuqiang Gao, Asaf Gilboa, Thomas Wolbers, Sandra E Black, R Shayna Rosenbaum
Our day-to-day experiences are often similar to one another, occurring in the same place at the same time of day, with common people and objects, and with a shared purpose. Humans have an episodic memory to represent unique, personal events that are rich in detail [1]. For this to occur, at least two basic neural mechanisms are required: one to orthogonalize or "separate" overlapping input patterns at encoding and another to reinstate or "complete" memories from partial cues at retrieval [2-6]. To what extent do these purported "pattern separation" and "pattern completion" mechanisms rely on distinct subfields of the hippocampus [6]? Computational models [4-6] and lesion and genetic studies in rodents [7-12] largely point to the dentate gyrus as responsible for pattern separation and the CA3 and CA1 subfields for pattern completion (but see [13-16])...
October 10, 2016: Current Biology: CB
Zhe Chen, Andres D Grosmark, Hector Penagos, Matthew A Wilson
Pyramidal neurons in the rodent hippocampus exhibit spatial tuning during spatial navigation, and they are reactivated in specific temporal order during sharp-wave ripples observed in quiet wakefulness or slow wave sleep. However, analyzing representations of sleep-associated hippocampal ensemble spike activity remains a great challenge. In contrast to wake, during sleep there is a complete absence of animal behavior, and the ensemble spike activity is sparse (low occurrence) and fragmental in time. To examine important issues encountered in sleep data analysis, we constructed synthetic sleep-like hippocampal spike data (short epochs, sparse and sporadic firing, compressed timescale) for detailed investigations...
2016: Scientific Reports
Timothy J Schoenfeld, Hayley C McCausland, Anup N Sonti, Heather A Cameron
Physical exercise reduces anxiety-like behavior in adult mice. The specific mechanisms that mediate this anxiolytic effect are unclear, but adult neurogenesis in the dentate gyrus has been implicated because it is robustly increased by running and has been linked to anxiodepressive-like behavior. We therefore tested the effects of long-term wheel running on anxiety-like behavior in GFAP-TK (TK) mice, a transgenic strain with complete ablation of adult neurogenesis. Five weeks of running reduced anxiety-like behavior equally in both TK mice and wild type (WT) control mice on two tests, elevated plus-maze and novelty-suppressed feeding...
November 2016: Hippocampus
Bernhard P Staresina, Sebastian Michelmann, Mathilde Bonnefond, Ole Jensen, Nikolai Axmacher, Juergen Fell
How do we retrieve vivid memories upon encountering a simple cue? Computational models suggest that this feat is accomplished by pattern completion processes involving the hippocampus. However, empirical evidence for hippocampal pattern completion and its underlying mechanisms has remained elusive. Here, we recorded direct intracranial EEG as human participants performed an associative memory task. For each study (encoding) and test (retrieval) event, we derived time-frequency resolved representational patterns in the hippocampus and compared the extent of pattern reinstatement for different mnemonic outcomes...
2016: ELife
Ravi L Rungta, Louis-Philippe Bernier, Lasse Dissing-Olesen, Christopher J Groten, Jeffrey M LeDue, Rebecca Ko, Sibyl Drissler, Brian A MacVicar
Astrocytes display complex morphologies with an array of fine extensions extending from the soma and the primary thick processes. Until the use of genetically encoded calcium indicators (GECIs) selectively expressed in astrocytes, Ca(2+) signaling was only examined in soma and thick primary processes of astrocytes where Ca(2+) -sensitive fluorescent dyes could be imaged. GECI imaging in astrocytes revealed a previously unsuspected pattern of spontaneous Ca(2+) transients in fine processes that has not been observed without chronic expression of GECIs, raising potential concerns about the effects of GECI expression...
August 1, 2016: Glia
(no author information available yet)
<strong>Objective </strong>To explore the temporal and spatial distribution of CCAAT/enhancer-binding protein homologous protein (CHOP) and calnexin (CNX) in the dentate gyrus of mesial temporal lobe epilepsy (mTLE) mouse model. <strong>Methods </strong>We used kainic acid (KA) to induce acute phase (12 h and 24 h) mTLE mouse models and performed Western blotting and immunofluorescence to detect the different expressions and distribution pattern of CHOP and CNX in CA3 of the hippocampus...
June 10, 2016: Zhongguo Yi Xue Ke Xue Yuan Xue Bao. Acta Academiae Medicinae Sinicae
Stella W Y Chan, Jessika E Sussmann, Liana Romaniuk, Tiffany Stewart, Stephen M Lawrie, Jeremy Hall, Andrew M McIntosh, Heather C Whalley
BACKGROUND: Studies have identified perturbations in facial processing in bipolar disorder and major depressive disorder (MDD), but their relationship to genetic risk and early development of illness is unclear. METHODS: The Scottish Bipolar Family Study is a prospective longitudinal investigation examining young individuals (age 16-25) at familial risk of mood disorder. Participants underwent functional MRI using an implicit facial processing task employing angry and neutral faces...
November 2016: Journal of Child Psychology and Psychiatry, and Allied Disciplines
Carol L Armstrong, Michael J Fisher, Yimei Li, Robert A Lustig, Jean B Belasco, Jane E Minturn, Christine E Hill-Kayser, Sonny Batra, Peter C Phillips
PURPOSE: Clinically effective measurement of cognitive toxicity from photon radiation therapy (XRT) should be accurate, sensitive, and specific. This pilot study tested translational findings on phasic changes in children's memory systems that are sensitive and insensitive to toxic XRT effects to identify a possible neuroplastic effect. METHODS AND MATERIALS: Memory processes were prospectively tested before XRT and at 3 later time points up to 2 years in 35 children with mixed primary brain tumors who had not experienced recurrence...
July 1, 2016: International Journal of Radiation Oncology, Biology, Physics
L Muessig, J Hauser, T J Wills, F Cacucci
Place cells are hippocampal pyramidal cells that are active when an animal visits a restricted area of the environment, and collectively their activity constitutes a neural representation of space. Place cell populations in the adult rat hippocampus display fundamental properties consistent with an associative memory network: the ability to 1) generate new and distinct spatial firing patterns when encountering novel spatial contexts or changes in sensory input ("remapping") and 2) reinstate previously stored firing patterns when encountering a familiar context, including on the basis of an incomplete/degraded set of sensory cues ("pattern completion")...
August 2016: Cerebral Cortex
Jason S Snyder, Laura Grigereit, Alexandra Russo, Désirée R Seib, Michelle Brewer, James Pickel, Heather A Cameron
The growth of research on adult neurogenesis and the development of new models and tools have greatly advanced our understanding of the function of newborn neurons in recent years. However, there are still significant limitations in the ability to identify the functions of adult neurogenesis in available models. Here we report a transgenic rat (TK rat) that expresses herpes simplex virus thymidine kinase in GFAP+ cells. Upon treating TK rats with the antiviral drug valganciclovir, granule cell neurogenesis can be completely inhibited in adulthood, in both the hippocampus and olfactory bulb...
May 2016: ENeuro
Xiao-Yi Xiong, Ting-Gang Wang, Mei-Hua Yang, Zhao-You Meng, Qing-Wu Yang, Fa-Xiang Wang
OBJECTIVE: Interleukin-21 (IL-21) is a cytokine that is an important modulator of immune responses. However, its roles in epilepsy are not completely clear. Here, we investigated the expression and distribution of IL-21 in a kainic acid (KA)-induced acute seizure mouse model. MATERIALS AND METHODS: Mice (n = 146) were randomly divided into an age-matched group, PBS injection group, and a KA injection group. The KA-injected mice were evaluated at 1, 3, and 24 h post-injection...
February 2016: Neurological Research
Maggie M Sweitzer, Charles F Geier, Merideth A Addicott, Rachel Denlinger, Bethany R Raiff, Jesse Dallery, F Joseph McClernon, Eric C Donny
The ventral and dorsal striatum are critical substrates of reward processing and motivation and have been repeatedly linked to addictive disorders, including nicotine dependence. However, little is known about how functional connectivity between these and other brain regions is modulated by smoking withdrawal and may contribute to relapse vulnerability. In the present study, 37 smokers completed resting state fMRI scans during both satiated and 24-h abstinent conditions, prior to engaging in a 3-week quit attempt supported by contingency management...
September 2016: Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology
Nicholas C Hindy, Felicia Y Ng, Nicholas B Turk-Browne
Models of predictive coding frame perception as a generative process in which expectations constrain sensory representations. These models account for expectations about how a stimulus will move or change from moment to moment, but do not address expectations about what other, distinct stimuli are likely to appear based on prior experience. We show that such memory-based expectations in human visual cortex are related to the hippocampal mechanism of pattern completion.
May 2016: Nature Neuroscience
Laura M Pidgeon, Alexa M Morcom
Pattern separation and pattern completion are fundamental brain processes thought to be critical for episodic memory encoding and retrieval, and for discrimination between similar memories. These processes are best understood in the hippocampus, but are proposed to occur throughout the brain, in particular in sensory regions. Cortical, as well as hippocampal, pattern separation may therefore support formation of event-unique memory traces. Using fMRI, we investigated cortical pattern separation and pattern completion and their relationship to encoding activity predicting subsequent item-specific compared to gist memory...
May 2016: Neuropsychologia
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