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Learning & Memory

Ana M M Oliveira
DNA methylation was traditionally viewed as a static mechanism required during cell fate determination. This view has been challenged and it is now accepted that DNA methylation is involved in the regulation of genomic responses in mature neurons, particularly in cognitive functions. The evidence for a role of DNA methylation in memory formation and maintenance comes from the increasing number of studies that have assessed the effects of manipulation of DNA methylation modifiers in the ability to form and maintain memories...
October 2016: Learning & Memory
Ashley M Blouin, Stephanie E Sillivan, Nadine F Joseph, Courtney A Miller
Prolonged distress and dysregulated memory processes are the core features of post-traumatic stress disorder (PTSD) and represent the debilitating, persistent nature of the illness. However, the neurobiological mechanisms underlying the expression of these symptoms are challenging to study in human patients. Stress-enhanced fear learning (SEFL) paradigms, which encompass both stress and memory components in rodents, are emerging as valuable preclinical models of PTSD. Rodent models designed to study the long-term mechanisms of either stress or fear memory alone have identified a critical role for numerous epigenetic modifications to DNA and histone proteins...
October 2016: Learning & Memory
Carolyn E Jones, Marie-H Monfils
Traumatic experiences early in life can contribute to the development of mood and anxiety disorders that manifest during adolescence and young adulthood. In young rats exposed to acute fear or stress, alterations in neural development can lead to enduring behavioral abnormalities. Here, we used a modified extinction intervention (retrieval+extinction) during late adolescence (post-natal day 45 [p45]), in rats, to target auditory Pavlovian fear associations acquired as juveniles (p17 and p25). The effects of adolescent intervention were examined by assessing freezing as adults during both fear reacquisition and social transmission of fear from a cagemate...
October 2016: Learning & Memory
Julie Boulanger Bertolus, Anne-Marie Mouly, Regina M Sullivan
As altricial infants gradually transition to adults, their proximate environment changes. In three short weeks, pups transition from a small world with the caregiver and siblings to a complex milieu rich in dangers as their environment expands. Such contrasting environments require different learning abilities and lead to distinct responses throughout development. Here, we will review some of the learned fear conditioned responses to threats in rats during their ontogeny, including behavioral and physiological measures that permit the assessment of learning and its supporting neurobiology from infancy through adulthood...
October 2016: Learning & Memory
Bianca A Silva, Cornelius T Gross, Johannes Gräff
How fear is represented in the brain has generated a lot of research attention, not only because fear increases the chances for survival when appropriately expressed but also because it can lead to anxiety and stress-related disorders when inadequately processed. In this review, we summarize recent progress in the understanding of the neural circuits processing innate fear in rodents. We propose that these circuits are contained within three main functional units in the brain: a detection unit, responsible for gathering sensory information signaling the presence of a threat; an integration unit, responsible for incorporating the various sensory information and recruiting downstream effectors; and an output unit, in charge of initiating appropriate bodily and behavioral responses to the threatful stimulus...
October 2016: Learning & Memory
Susana S Correia, Ki A Goosens
Reward and punishment are often thought of as opposing processes: rewards and the environmental cues that predict them elicit approach and consummatory behaviors, while punishments drive aversion and avoidance behaviors. This framework suggests that there may be segregated brain circuits for these valenced behaviors. The basolateral amygdala (BLA) is one brain region that contributes to both types of motivated behavior. Individual neurons in the BLA can favor positive over negative valence, or vice versa, but these neurons are intermingled, showing no anatomical segregation...
October 2016: Learning & Memory
Munir Gunes Kutlu, Thomas J Gould
It has long been hypothesized that conditioning mechanisms play major roles in addiction. Specifically, the associations between rewarding properties of drugs of abuse and the drug context can contribute to future use and facilitate the transition from initial drug use into drug dependency. On the other hand, the self-medication hypothesis of drug abuse suggests that negative consequences of drug withdrawal result in relapse to drug use as an attempt to alleviate the negative symptoms. In this review, we explored these hypotheses and the involvement of the hippocampus in the development and maintenance of addiction to widely abused drugs such as cocaine, amphetamine, nicotine, alcohol, opiates, and cannabis...
October 2016: Learning & Memory
Heidi C Meyer, David J Bucci
Response inhibition is an important component of adaptive behavior. Substantial prior research has focused on reactive inhibition, which refers to the cessation of a motor response that is already in progress. More recently, a growing number of studies have begun to examine mechanisms underlying proactive inhibition, whereby preparatory processes result in a response being withheld before it is initiated. It has become apparent that proactive inhibition is an essential component of the overall ability to regulate behavior and has implications for the success of reactive inhibition...
October 2016: Learning & Memory
Evan L Ardiel, Andrew C Giles, Alex J Yu, Theodore H Lindsay, Shawn R Lockery, Catharine H Rankin
Habituation is a highly conserved phenomenon that remains poorly understood at the molecular level. Invertebrate model systems, like Caenorhabditis elegans, can be a powerful tool for investigating this fundamental process. Here we established a high-throughput learning assay that used real-time computer vision software for behavioral tracking and optogenetics for stimulation of the C. elegans polymodal nociceptor, ASH. Photoactivation of ASH with ChR2 elicited backward locomotion and repetitive stimulation altered aspects of the response in a manner consistent with habituation...
October 2016: Learning & Memory
Yang-Jung Yu, Chien-Hsuan Huang, Chih-Hua Chang, Po-Wu Gean
Destabilization refers to a memory that becomes unstable when reactivated and is susceptible to disruption by amnestic agents. Here we delineated the cellular mechanism underlying the destabilization of drug memory. Mice were conditioned with methamphetamine (MeAM) for 3 d, and drug memory was assessed with a conditioned place preference (CPP) protocol. Anisomycin (ANI) was administered 60 min after the CPP retrieval to disrupt reconsolidation. We found that destabilization of MeAM CPP after the application of ANI was blocked by the N-methyl-d-aspartate receptor (NMDAR) antagonist MK-801 and the NR2B antagonist ifenprodil (IFN) but not by the NR2A antagonist NVP-AAM077 (NVP)...
September 2016: Learning & Memory
Xiaoqun Zhang, Ning Yao, Karima Chergui
Several forms of long-term depression (LTD) of glutamatergic synaptic transmission have been identified in the dorsal striatum and in the nucleus accumbens (NAc). Such experience-dependent synaptic plasticity might play important roles in reward-related learning. The GABAA receptor agonist muscimol was recently found to trigger a long-lasting depression of glutamatergic synaptic transmission in the NAc of adolescent mice, but the mechanisms that underlie this novel form of LTD were not studied. Here we examined the effect of muscimol applied in the perfusion solution on the amplitude of field excitatory postsynaptic potentials/population spikes (fEPSP/PSs) in mouse brain slices...
September 2016: Learning & Memory
Roque I Ferrer Monti, Marcelo Giachero, Joaquín M Alfei, Adrián M Bueno, Gabriel Cuadra, Victor A Molina
It is known that a consolidated memory can return to a labile state and become transiently malleable following reactivation. This instability is followed by a restabilization phase termed reconsolidation. In this work, we explored whether an unrelated appetitive experience (voluntary consumption of diluted sucrose) can affect a contextual fear memory in rats during the reactivation-induced destabilization phase. Our findings show that exposure to an appetitive experience following reactivation can diminish fear retention...
September 2016: Learning & Memory
Costas Papatheodoropoulos, Stylianos Kouvaros
The ability of the ventral hippocampus (VH) for long-lasting long-term potentiation (LTP) and the mechanisms underlying its lower ability for short-lasting LTP compared with the dorsal hippocampus (DH) are unknown. Using recordings of field excitatory postsynaptic potentials (EPSPs) from the CA1 field of adult rat hippocampal slices, we found that 200-Hz stimulation induced nondecremental LTP that was maintained for at least 7 h and was greater in the DH than in the VH. The interaction of NMDA receptors with L-type voltage-dependent calcium channels appeared to be more effective in the DH than in the VH...
September 2016: Learning & Memory
Ryan Bottary, Akshata Sonni, David Wright, Rebecca M C Spencer
Sleep enhances motor sequence learning (MSL) in young adults by concatenating subsequences ("chunks") formed during skill acquisition. To examine whether this process is reduced in aging, we assessed performance changes on the MSL task following overnight sleep or daytime wake in healthy young and older adults. Young adult performance enhancement was correlated with nREM2 sleep, and facilitated by preferential improvement of slowest within-sequence transitions. This effect was markedly reduced in older adults, and accompanied by diminished sigma power density (12-15 Hz) during nREM2 sleep, suggesting that diminished chunk concatenation following sleep may underlie reduced consolidation of MSL in older adults...
September 2016: Learning & Memory
Joshua K Carr, Neil M Fournier, Hugo Lehmann
We examined whether increasing retrieval difficulty in a spatial memory task would promote the recruitment of the anterior cingulate cortex (ACC) similar to what is typically observed during remote memory retrieval. Rats were trained on the hidden platform version of the Morris Water Task and tested three or 30 d later. Retrieval difficulty was manipulated by removing several prominent extra-pool cues from the testing room. Immediate early gene expression (c-Fos) in the ACC was greater following the cue removal and comparable to remote memory retrieval (30-d retention interval) levels, supporting the view of increased ACC contribution during high cognitive-demand memory processes...
September 2016: Learning & Memory
Fei Zheng, Ming Zhang, Qi Ding, Ferzin Sethna, Lily Yan, Changjong Moon, Miyoung Yang, Hongbing Wang
Mental health and cognitive functions are influenced by both genetic and environmental factors. Although having active lifestyle with physical exercise improves learning and memory, how it interacts with the specific key molecular regulators of synaptic plasticity is largely unknown. Here, we examined the effects of voluntary running on long-term potentiation (LTP) and memory formation in mice lacking type 1 adenylyl cyclase (AC1), a neurospecific synaptic enzyme that contributes to Ca(2+)-stimulated cAMP production...
August 2016: Learning & Memory
Seonil Kim, Joseph E Pick, Sinedu Abera, Latika Khatri, Danielle D P Ferreira, Matheus F Sathler, Sage L Morison, Franz Hofmann, Edward B Ziff
Phosphorylation of GluA1, a subunit of AMPA receptors (AMPARs), is critical for AMPAR synaptic trafficking and control of synaptic transmission. cGMP-dependent protein kinase II (cGKII) mediates this phosphorylation, and cGKII knockout (KO) affects GluA1 phosphorylation and alters animal behavior. Notably, GluA1 phosphorylation in the KO hippocampus is increased as a functional compensation for gene deletion, while such compensation is absent in the prefrontal cortex. Thus, there are brain region-specific effects of cGKII KO on AMPAR trafficking, which could affect animal behavior...
August 2016: Learning & Memory
Yanil Hepp, Angeles Salles, Martin Carbo-Tano, Maria Eugenia Pedreira, Ramiro Freudenthal
The aim of the present study was to analyze the surface expression of the NMDA-like receptors during the consolidation of contextual learning in the crab Neohelice granulata Memory storage is based on alterations in the strength of synaptic connections between neurons. The glutamatergic synapses undergo various forms of N-methyl-D aspartate receptor (NMDAR)-dependent changes in strength, a process that affects the abundance of other receptors at the synapse and underlies some forms of learning and memory. Here we propose a direct regulation of the NMDAR...
August 2016: Learning & Memory
Corinna Roschlau, Angeline Votteler, Wolfgang Hauber
Here we tested in rats effects of the procognitive drugs modafinil and methylphenidate on post-acquisition performance in an object-location paired-associates learning (PAL) task. Modafinil (32; 64 mg/kg) was without effect, while higher (9 mg/kg) but not lower (4.5 mg/kg) doses of methylphenidate impaired PAL performance. Likewise, higher but not lower doses of amphetamine (0.4; 0.8 mg/kg) and MK-801 (0.08; 0.12 mg/kg) decreased PAL performance. Impaired PAL performance induced by methylphenidate, amphetamine, and MK801 most likely reflects compromised cognitive function, e...
August 2016: Learning & Memory
Stephanie L Leal, Jessica A Noche, Elizabeth A Murray, Michael A Yassa
Numerous studies have suggested that older adults preferentially remember positive information ("positivity effect"), however others have reported mixed results. One potential source of conflict is that aging is not a unitary phenomenon and individual differences exist. We modified a standard neuropsychological test to vary emotional content and tested memory at three time points (immediate/20 min/1 wk). Cognitively normal older adults were stratified into those with and without subclinical memory impairment...
August 2016: Learning & Memory
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