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Pattern completion and hippocampus

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 mouse with completely ablated neurogenesis. Five weeks of running reduced anxiety-like behavior equally in both TK mice and wild type (WT) control mice on two tests of anxiety-like behavior, elevated plus-maze and novelty-suppressed feeding...
August 29, 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...
July 15, 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
Alexa Tompary, Katherine Duncan, Lila Davachi
Episodic memory involves remembering the details that characterize a prior experience. Successful memory recovery has been associated with the reinstatement of brain activity patterns in a number of sensory regions across the cortex. However, how the hippocampus and surrounding medial temporal lobe (MTL) cortex contribute to this process is less clear. Models of episodic memory posit that hippocampal pattern reinstatement, also referred to as pattern completion, may mediate cortical reinstatement during retrieval...
August 2016: Hippocampus
Laura E Korthauer, Nicole T Nowak, Scott D Moffat, Yang An, Laura M Rowland, Peter B Barker, Susan M Resnick, Ira Driscoll
Despite considerable evidence for deleterious effects of aging on place learning and memory, less is known about the trajectory and the putative neural mechanisms of these decrements. The virtual Morris water task (vMWT) is a human analog of a nonhuman spatial navigation task. The present study investigated longitudinal changes in place learning in 51 healthy, nondemented adults (age 30-83 years) who completed the vMWT and a neuropsychological battery at 2 time-points (interval = ∼8 years). We also assessed cross-sectional associations between vMWT and brain structure, biochemical integrity, and standardized neuropsychological measures in a subset of 22 individuals who underwent magnetic resonance imaging at follow-up...
March 2016: Neurobiology of Aging
Amelia Toesca, Maria Concetta Geloso, Adriana Maria Mongiovì, Alfredo Furno, Arcangelo Schiattarella, Fabrizio Michetti, Valentina Corvino
Reelin is an extracellular matrix glycoprotein involved in the modulation of synaptic plasticity and essential for the proper radial migration of cortical neurons during development and for the integration and positioning of dentate granular cell progenitors; its expression is down-regulated as brain maturation is completed. Trimethyltin (TMT) is a potent neurotoxicant which causes selective neuronal death mainly localised in the CA1-CA3/hilus hippocampal regions. In the present study we analysed the expression of reelin and the modulation of endogenous neurogenesis in the postnatal rat hippocampus during TMT-induced neurodegeneration (TMT 6 mg/kg)...
July 2016: Neurochemical Research
Tzu-Ching E Lin, Natasha M Dumigan, Mark Good, Robert C Honey
Successful retrieval of a memory for an entire pattern of stimulation by the presentation of a fragment of that pattern is a critical facet of memory function. We examined processes of pattern completion using novel sensory preconditioning procedures in rats that had either received sham lesions (group Sham) or lesions of the hippocampus (group HPC). After exposure to two audio-visual patterns (AX and BY) rats received fear conditioning with X (but not Y). Subsequent tests assessed fear to stimulus compounds (e...
April 2016: Neurobiology of Learning and Memory
Julia A Rao, Lisanne M Jenkins, Erica Hymen, Maia Feigon, Sara L Weisenbach, Jon-Kar Zubieta, Scott A Langenecker
OBJECTIVES: There is a well-known association between memory impairment and major depressive disorder (MDD). Additionally, recent studies are also showing resting-state functional magnetic resonance imaging (rsMRI) abnormalities in active and remitted MDD. However, no studies to date have examined both rs connectivity and memory performance in early course remitted MDD, nor the relationship between connectivity and semantically cued episodic memory. METHODS: The rsMRI data from two 3...
February 2016: Journal of the International Neuropsychological Society: JINS
Vanessa Lux, Erika Atucha, Takashi Kitsukawa, Magdalena M Sauvage
Whether retrieval still depends on the hippocampus as memories age or relies then on cortical areas remains a major controversy. Despite evidence for a functional segregation between CA1, CA3 and parahippocampal areas, their specific role within this frame is unclear. Especially, the contribution of CA3 is questionable as very remote memories might be too degraded to be used for pattern completion. To identify the specific role of these areas, we imaged brain activity in mice during retrieval of recent, early remote and very remote fear memories by detecting the immediate-early gene Arc...
2016: ELife
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