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Learning & Memory

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https://www.readbyqxmd.com/read/28096499/when-eye-movements-express-memory-for-old-and-new-scenes-in-the-absence-of-awareness-and-independent-of-hippocampus
#1
Christine N Smith, Larry R Squire
Eye movements can reflect memory. For example, participants make fewer fixations and sample fewer regions when viewing old versus new scenes (the repetition effect). It is unclear whether the repetition effect requires that participants have knowledge (awareness) of the old-new status of the scenes or if it can occur independent of knowledge about old-new status. It is also unclear whether the repetition effect is hippocampus-dependent or hippocampus-independent. A complication is that testing conscious memory for the scenes might interfere with the expression of unconscious (unaware), experience-dependent eye movements...
February 2017: Learning & Memory
https://www.readbyqxmd.com/read/28096498/differential-changes-in-hippocampal-camkii-and-glua1-activity-after-memory-training-involving-different-levels-of-adaptive-forgetting
#2
Nicolas Fraize, Al Mahdy Hamieh, Mickaël Antoine Joseph, Monique Touret, Régis Parmentier, Paul Antoine Salin, Gaël Malleret
Phosphorylation of CaMKII and AMPA receptor GluA1 subunit has been shown to play a major role in hippocampal-dependent long-term/reference memory (RM) and in the expression of long-term synaptic potentiation (LTP). In contrast, it has been proposed that dephosphorylation of these proteins could be involved in the opposite phenomenon of hippocampal long-term synaptic depression (LTD) and in adaptive forgetting. Adaptive forgetting allows interfering old memories to be forgotten to give new ones the opportunity to be stored in memory, and in particular in short-term/working memory (WM) that was shown to be very sensitive to proactive interference...
February 2017: Learning & Memory
https://www.readbyqxmd.com/read/28096497/bdnf-regains-function-in-hippocampal-long-term-potentiation-deficits-caused-by-diencephalic-damage
#3
Lindsey C Vedder, Lisa M Savage
Thiamine deficiency (TD), commonly associated with chronic alcoholism, leads to diencephalic damage, hippocampal dysfunction, and spatial learning and memory deficits. We show a decrease in the magnitude of long-term potentiation (LTP) and paired-pulse facilitation (PPF) at CA3-CA1 synapses, independent of sex, following diencephalic damage induced by TD in rats. Thus, despite a lack of extensive hippocampal cell loss, diencephalic brain damage down-regulates plastic processes within the hippocampus, likely contributing to impaired hippocampal-dependent behaviors...
February 2017: Learning & Memory
https://www.readbyqxmd.com/read/28096496/a-reminder-of-extinction-reduces-relapse-in-an-animal-model-of-voluntary-behavior
#4
Javier Nieto, Metin Uengoer, Rodolfo Bernal-Gamboa
One experiment with rats explored whether an extinction-cue prevents the recovery of extinguished lever-pressing responses. Initially, rats were trained to perform one instrumental response (R1) for food in Context A, and a different instrumental response (R2) in Context B. Then, responses were extinguished each in the alternate context (R1 in Context B; R2 in Context A). For one group, extinction of both responses was conducted in the presence of an extinction-cue, whereas in a second group, the extinction-cue only accompanied extinction of R1...
February 2017: Learning & Memory
https://www.readbyqxmd.com/read/28096495/memory-disrupting-effects-of-nonmuscle-myosin-ii-inhibition-depend-on-the-class-of-abused-drug-and-brain-region
#5
Sherri B Briggs, Ashley M Blouin, Erica J Young, Gavin Rumbaugh, Courtney A Miller
Depolymerizing actin in the amygdala through nonmuscle myosin II inhibition (NMIIi) produces a selective, lasting, and retrieval-independent disruption of the storage of methamphetamine-associated memories. Here we report a similar disruption of memories associated with amphetamine, but not cocaine or morphine, by NMIIi. Reconsolidation appeared to be disrupted with cocaine. Unlike in the amygdala, methamphetamine-associated memory storage was not disrupted by NMIIi in the hippocampus, nucleus accumbens, or orbitofrontal cortex...
February 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980078/reward-retroactively-enhances-memory-consolidation-for-related-items
#6
Anuya Patil, Vishnu P Murty, Joseph E Dunsmoor, Elizabeth A Phelps, Lila Davachi
Reward motivation has been shown to modulate episodic memory processes in order to support future adaptive behavior. However, for a memory system to be truly adaptive, it should enhance memory for rewarded events as well as for neutral events that may seem inconsequential at the time of encoding but can gain importance later. Here, we investigated the influence of reward motivation on retroactive memory enhancement selectively for conceptually related information. We found behavioral evidence that reward retroactively enhances memory at a 24-h memory test, but not at an immediate memory test, suggesting a role for post-encoding mechanisms of consolidation...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980077/role-of-proteasome-dependent-protein-degradation-in-long-term-operant-memory-in-aplysia
#7
Lisa C Lyons, Jacob S Gardner, Catherine E Gandour, Harini C Krishnan
We investigated the in vivo role of protein degradation during intermediate (ITM) and long-term memory (LTM) in Aplysia using an operant learning paradigm. The proteasome inhibitor MG-132 inhibited the induction and molecular consolidation of LTM with no effect on ITM. Remarkably, maintenance of steady-state protein levels through inhibition of protein synthesis using either anisomycin or rapamycin in conjunction with proteasome inhibition permitted the formation of robust 24 h LTM. Our studies suggest a primary role for proteasomal activity in facilitation of gene transcription for LTM and raise the possibility that synaptic mechanisms are sufficient to sustain 24 h memory...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980076/primary-auditory-cortex-regulates-threat-memory-specificity
#8
Mattis B Wigestrand, Hillary C Schiff, Marianne Fyhn, Joseph E LeDoux, Robert M Sears
Distinguishing threatening from nonthreatening stimuli is essential for survival and stimulus generalization is a hallmark of anxiety disorders. While auditory threat learning produces long-lasting plasticity in primary auditory cortex (Au1), it is not clear whether such Au1 plasticity regulates memory specificity or generalization. We used muscimol infusions in rats to show that discriminatory threat learning requires Au1 activity specifically during memory acquisition and retrieval, but not during consolidation...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980075/effects-of-context-preexposure-and-delay-until-anxiety-retrieval-on-generalization-of-contextual-anxiety
#9
Marta Andreatta, Dorothea Neueder, Evelyn Glotzbach-Schoon, Andreas Mühlberger, Paul Pauli
Animal studies suggest that time delay between acquisition and retrieval of contextual anxiety increases generalization. Moreover, such generalization is prevented by preexposure to the context (CTX), presumably due to an improved representation of such context. We investigated whether preexposure and time-passing modulate generalization of contextual anxiety, in humans. On Day 1, 42 participants (preexposure group) explored two virtual offices, while 41 participants (no-preexposure group) explored a virtual stadium...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980074/vagus-nerve-stimulation-reduces-cocaine-seeking-and-alters-plasticity-in-the-extinction-network
#10
Jessica E Childs, Jaime DeLeon, Emily Nickel, Sven Kroener
Drugs of abuse cause changes in the prefrontal cortex (PFC) and associated regions that impair inhibitory control over drug-seeking. Breaking the contingencies between drug-associated cues and the delivery of the reward during extinction learning reduces rates of relapse. Here we used vagus nerve stimulation (VNS) to induce targeted synaptic plasticity to facilitate extinction of appetitive behaviors and to reduce relapse. Rats self-administered cocaine and were given VNS during extinction. Relapse to drug-seeking was assessed in a cued reinstatement session...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980073/respective-role-of-the-dorsal-hippocampus-and-the-entorhinal-cortex-during-the-recombination-of-previously-learned-olfactory-tactile-associations-in-the-rat
#11
Lise Boisselier, Barbara Ferry, Rémi Gervais
The hippocampal formation has been extensively described as a key component for object recognition in conjunction with place and context. The present study aimed at describing neural mechanisms in the hippocampal formation that support olfactory-tactile (OT) object discrimination in a task where space and context were not taken into account. The task consisted in discriminating one baited cup among three, each of them presenting overlapping olfactory or tactile elements. The experiment tested the involvement of the entorhinal cortex (EC) and the dorsal hippocampus (DH) in the acquisition of this cross-modal task, either with new items or with familiar but recombined items...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980072/memory-trace-reactivation-and-behavioral-response-during-retrieval-are-differentially-modulated-by-amygdalar-glutamate-receptors-activity-interaction-between-amygdala-and-insular-cortex
#12
Daniel Osorio-Gómez, Kioko Guzmán-Ramos, Federico Bermúdez-Rattoni
The insular cortex (IC) is required for conditioned taste aversion (CTA) retrieval. However, it remains unknown which cortical neurotransmitters levels are modified upon CTA retrieval. Using in vivo microdialysis, we observed that there were clear elevations in extracellular glutamate, norepinephrine, and dopamine in and around the center of the gustatory zone of the IC during CTA retrieval. Additionally, it has been reported that the amygdala-IC interaction is highly involved in CTA memory establishment. Therefore, we evaluated the effects of infusions of an AMPA receptor antagonist (CNQX) and a NMDA receptor antagonist (APV) into the amygdala on CTA retrieval and IC neurotransmitter levels...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27980071/a-pkm-generated-by-calpain-cleavage-of-a-classical-pkc-is-required-for-activity-dependent-intermediate-term-facilitation-in-the-presynaptic-sensory-neuron-of-aplysia
#13
Carole A Farah, Margaret H Hastings, Tyler W Dunn, Katrina Gong, Danay Baker-Andresen, Wayne S Sossin
Atypical PKM, a persistently active form of atypical PKC, is proposed to be a molecular memory trace, but there have been few examinations of the role of PKMs generated from other PKCs. We demonstrate that inhibitors used to inhibit PKMs generated from atypical PKCs are also effective inhibitors of other PKMs. In contrast, we demonstrate that dominant-negative PKMs show isoform-specificity. A dominant-negative PKM from the classical PKC Apl I blocks activity-dependent intermediate-term facilitation (a-ITF) when expressed in the sensory neuron, while a dominant-negative PKM from the atypical PKC Apl III does not...
January 2017: Learning & Memory
https://www.readbyqxmd.com/read/27918278/pi3-kinase-cascade-has-a-differential-role-in-acquisition-and-extinction-of-conditioned-fear-memory-in-juvenile-and-adult-rats
#14
Ilana Slouzkey, Mouna Maroun
The basolateral amygdala (BLA), medial prefrontal cortex (mPFC) circuit, plays a crucial role in acquisition and extinction of fear memory. Extinction of aversive memories is mediated, at least in part, by the phosphoinositide-3 kinase (PI3K)/Akt pathway in adult rats. There is recent interest in the neural mechanisms that mediate fear and extinction in juvenile animals and whether these mechanisms are distinctive from those in adult animals. In the present study, we examined (1) changes in phosphorylation of Akt in the BLA and mPFC after fear conditioning and extinction in juvenile and adult rats and (2) the effect of BLA and mPFC localized inhibition of the PI3K following acquisition and extinction of contextual fear memory...
December 2016: Learning & Memory
https://www.readbyqxmd.com/read/27918277/computational-model-of-a-positive-bdnf-feedback-loop-in-hippocampal-neurons-following-inhibitory-avoidance-training
#15
Yili Zhang, Paul Smolen, Cristina M Alberini, Douglas A Baxter, John H Byrne
Inhibitory avoidance (IA) training in rodents initiates a molecular cascade within hippocampal neurons. This cascade contributes to the transition of short- to long-term memory (i.e., consolidation). Here, a differential equation-based model was developed to describe a positive feedback loop within this molecular cascade. The feedback loop begins with an IA-induced release of brain-derived neurotrophic factor (BDNF), which in turn leads to rapid phosphorylation of the cAMP response element-binding protein (pCREB), and a subsequent increase in the level of the β isoform of the CCAAT/enhancer binding protein (C/EBPβ)...
December 2016: Learning & Memory
https://www.readbyqxmd.com/read/27918276/repeated-recall-and-pkm%C3%AE-maintain-fear-memories-in-juvenile-rats
#16
Chicora F Oliver, Patricia Kabitzke, Peter Serrano, Laura J Egan, Gordon A Barr, Harry N Shair, Christoph Wiedenmayer
We examined the neural substrates of fear memory formation and maintenance when repeated recall was used to prevent forgetting in young animals. In contrast to adult rats, juveniles failed to show contextual fear responses at 4 d post-fear conditioning. Reconsolidation sessions 3 and 6 d after conditioning restored contextual fear responses in juveniles 7 d after initial training. In juveniles that received reconsolidation sessions, protein kinase M zeta (PKMζ) increased in the amygdala, but not in the hippocampus...
December 2016: Learning & Memory
https://www.readbyqxmd.com/read/27918275/behavioral-mechanisms-of-context-fear-generalization-in-mice
#17
Kylie A Huckleberry, Laura B Ferguson, Michael R Drew
There is growing interest in generalization of learned contextual fear, driven in part by the hypothesis that mood and anxiety disorders stem from impaired hippocampal mechanisms of fear generalization and discrimination. However, there has been relatively little investigation of the behavioral and procedural mechanisms that might control generalization of contextual fear. We assessed the relative contribution of different contextual features to context fear generalization and characterized how two common conditioning protocols-foreground (uncued) and background (cued) contextual fear conditioning-affected context fear generalization...
December 2016: Learning & Memory
https://www.readbyqxmd.com/read/27918274/stable-long-term-spatial-memory-in-young-and-aged-rats-achieved-with-a-one-day-morris-water-maze-training-protocol
#18
Ruth M Barrientos, Meagan M Kitt, Heather M D'Angelo, Linda R Watkins, Jerry W Rudy, Steven F Maier
Here, we present data demonstrating that a 1 d Morris water maze training protocol is effective at producing stable, long-term spatial memory in both young (3 mo old) and aged (24 mo old) F344xBN rats. Four trials in each of four sessions separated by a 2.5 h ISI produced robust selective search for the platform 1 and 4 d after training, in both age groups. A 1 h ISI protocol did not produce good retention. Also, compressing the trials into just two sessions separated by a 2.5 h ISI produced limited retention in only young rats...
December 2016: Learning & Memory
https://www.readbyqxmd.com/read/27918273/neural-circuits-via-which-single-prolonged-stress-exposure-leads-to-fear-extinction-retention-deficits
#19
Dayan Knox, Briana R Stanfield, Jennifer M Staib, Nina P David, Samantha M Keller, Thomas DePietro
Single prolonged stress (SPS) has been used to examine mechanisms via which stress exposure leads to post-traumatic stress disorder symptoms. SPS induces fear extinction retention deficits, but neural circuits critical for mediating these deficits are unknown. To address this gap, we examined the effect of SPS on neural activity in brain regions critical for extinction retention (i.e., fear extinction circuit). These were the ventral hippocampus (vHipp), dorsal hippocampus (dHipp), basolateral amygdala (BLA), prelimbic cortex (PL), and infralimbic cortex (IL)...
December 2016: Learning & Memory
https://www.readbyqxmd.com/read/27918272/rats-can-acquire-conditional-fear-of-faint-light-leaking-through-the-acrylic-resin-used-to-mount-fiber-optic-cannulas
#20
Adam Eckmier, Willy Daney de Marcillac, Agnès Maître, Thérèse M Jay, Matthew J Sanders, Bill P Godsil
Rodents are exquisitely sensitive to light and optogenetic behavioral experiments routinely introduce light-delivery materials into experimental situations, which raises the possibility that light could leak and influence behavioral performance. We examined whether rats respond to a faint diffusion of light, termed caplight, which emanated through the translucent dental acrylic resin used to affix deep-brain optical cannulas in place. Although rats did not display significant changes in locomotion or rearing to caplight in a darkened open field, they did acquire conditional fear via caplight-footshock pairings...
December 2016: Learning & Memory
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