Publications by authors named "Cristina M Alberini"

68 Publications

Editorial.

Hippocampus 2021 Jun 14. Epub 2021 Jun 14.

Center for Neural Science, New York University, USA.

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http://dx.doi.org/10.1002/hipo.23371DOI Listing
June 2021

Associative memory persistence in 3- to 5-year-olds.

Dev Sci 2021 Feb 24:e13105. Epub 2021 Feb 24.

Department of Psychology, New York University, New York, NY, USA.

Adults struggle to recollect episodic memories from early life. This phenomenon-referred to as "infantile" and "childhood amnesia"-has been widely observed across species and is characterized by rapid forgetting from birth until early childhood. While a number of studies have focused on infancy, few studies have examined the persistence of memory for newly learned associations during the putative period of childhood amnesia. In this study, we investigated forgetting in 137 children ages 3-5 years old by using an interactive storybook task. We assessed associative memory between subjects after 5-min, 24-h, and 1-week delay periods. Across all delays, we observed a significant increase in memory performance with age. While all ages demonstrated above-chance memory performance after 5-min and 24-h delays, we observed chance-level memory accuracy in 3-year-olds following a 1-week delay. The observed age differences in associative memory support the proposal that hippocampal-dependent memory systems undergo rapid development during the preschool years. These data have the potential to inform future work translating memory persistence and malleability research from rodent models to humans by establishing timescales at which we expect young children to forget newly learned associations.
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http://dx.doi.org/10.1111/desc.13105DOI Listing
February 2021

Distinct Transcriptomic Profiles in the Dorsal Hippocampus and Prelimbic Cortex Are Transiently Regulated following Episodic Learning.

J Neurosci 2021 Mar 3;41(12):2601-2614. Epub 2021 Feb 3.

Center for Neural Science, New York University, New York, New York 10003

A fundamental, evolutionarily conserved biological mechanism required for long-term memory formation is rapid induction of gene transcription upon learning in relevant brain areas. For episodic types of memories, two regions undergoing this transcription are the dorsal hippocampus (dHC) and prelimbic (PL) cortex. Whether and to what extent these regions regulate similar or distinct transcriptomic profiles upon learning remain to be understood. Here, we used RNA sequencing in the dHC and PL cortex of male rats to profile their transcriptomes in untrained conditions (baseline) and at 1 h and 6 d after inhibitory avoidance learning. We found that, of 33,713 transcripts, >14,000 were significantly expressed at baseline in both regions and ∼3000 were selectively enriched in each region. Gene Ontology biological pathway analyses indicated that commonly expressed pathways included synapse organization, regulation of membrane potential, and vesicle localization. The enriched pathways in the dHC were gliogenesis, axon development, and lipid modification, while in the PL cortex included vesicle localization and synaptic vesicle cycle. At 1 h after learning, 135 transcripts changed significantly in the dHC and 478 in the PL cortex; of these, only 34 were shared. Biological pathways most significantly regulated by learning in the dHC were protein dephosphorylation, glycogen and glucan metabolism, while in the PL cortex were axon development and axonogenesis. The transcriptome profiles returned to baseline by 6 d after training. Thus, a significant portion of dHC and PL cortex transcriptomic profiles is divergent, and their regulation upon learning is largely distinct and transient. Long-term episodic memory formation requires gene transcription in several brain regions, including the hippocampus and PFC. The comprehensive profiles of the dynamic mRNA changes that occur in these regions following learning are not well understood. Here, we performed RNA sequencing in the dorsal hippocampus and prelimbic cortex, a PFC subregion, at baseline, 1 h, and 6 d after episodic learning in rats. We found that, at baseline, dorsal hippocampus and prelimbic cortex differentially express a significant portion of mRNAs. Moreover, learning produces a transient regulation of region-specific profiles of mRNA, indicating that unique biological programs in different brain regions underlie memory formation.
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http://dx.doi.org/10.1523/JNEUROSCI.1557-20.2021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8018728PMC
March 2021

The Ontogeny of Hippocampus-Dependent Memories.

J Neurosci 2021 02 16;41(5):920-926. Epub 2020 Dec 16.

Temple University, 19122, Philadelphia, Pennsylvania.

The formation of memories that contain information about the specific time and place of acquisition, which are commonly referred to as "autobiographical" or "episodic" memories, critically relies on the hippocampus and on a series of interconnected structures located in the medial temporal lobe of the mammalian brain. The observation that adults retain very few of these memories from the first years of their life has fueled a long-standing debate on whether infants can make the types of memories that in adults are processed by the hippocampus-dependent memory system, and whether the hippocampus is involved in learning and memory processes early in life. Recent evidence shows that, even at a time when its circuitry is not yet mature, the infant hippocampus is able to produce long-lasting memories. However, the ability to acquire and store such memories relies on molecular pathways and network-based activity dynamics different from the adult system, which mature with age. The mechanisms underlying the formation of hippocampus-dependent memories during infancy, and the role that experience exerts in promoting the maturation of the hippocampus-dependent memory system, remain to be understood. In this review, we discuss recent advances in our understanding of the ontogeny and the biological correlates of hippocampus-dependent memories.
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http://dx.doi.org/10.1523/JNEUROSCI.1651-20.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7880290PMC
February 2021

CIM6P/IGF-2 Receptor Ligands Reverse Deficits in Angelman Syndrome Model Mice.

Autism Res 2021 01 27;14(1):29-45. Epub 2020 Oct 27.

Center for Neural Science, New York University, New York, New York, USA.

Angelman syndrome (AS), a genetic disorder that primarily affects the nervous system, is characterized by delayed development, intellectual disability, severe speech impairment, and problems with movement and balance (ataxia). Most affected children also have recurrent seizures (epilepsy). No existing therapies are capable of comprehensively treating the deficits in AS; hence, there is an urgent need to identify new treatments. Here we show that insulin-like growth factor 2 (IGF-2) and mannose-6-phosphate (M6P), ligands of two independent binding sites of the cation-independent M6P/IGF-2 receptor (CIM6P/IGF-2R), reverse most major deficits of AS modeled in mice. Subcutaneous injection of IGF-2 or M6P in mice modeling AS restored cognitive impairments as assessed by measurements of contextual and recognition memories, motor deficits assessed by rotarod and hindlimb clasping, and working memory/flexibility measured by Y-maze. IGF-2 also corrected deficits in marble burying and significantly attenuated acoustically induced seizures. An observational battery of tests confirmed that neither ligand changed basic functions including physical characteristics, general behavioral responses, and sensory reflexes, indicating that they are relatively safe. Our data provide strong preclinical evidence that targeting CIM6P/IGF-2R is a promising approach for developing novel therapeutics for AS. LAY SUMMARY: There is no effective treatment for the neurodevelopmental disorder Angelman syndrome (AS). Using a validated AS mouse model, the Ube3a , in this study we show that systemic administration of ligands of the cation independent mannose-6-phosphate receptor, also known as insulin-like growth factor 2 receptor (CIM6P/IGF-2R) reverses cognitive impairment, motor deficits, as well as seizures associated with AS. Thus, ligands that activate the CIM6P/IGF-2R may represent novel, potential therapeutic targets for AS.
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http://dx.doi.org/10.1002/aur.2418DOI Listing
January 2021

Autophagy coupled to translation is required for long-term memory.

Autophagy 2020 Jun 17:1-22. Epub 2020 Jun 17.

Center for Neural Science, New York University, New York, NY, USA.

An increase in protein synthesis following learning is a fundamental and evolutionarily conserved mechanism of long-term memory. To maintain homeostasis, this protein synthesis must be counterbalanced by mechanisms such as protein degradation. Recent studies reported that macroautophagy/autophagy, a major protein degradation mechanism, is required for long-term memory formation. However, how learning regulates autophagy and recruits it into long-term memory formation remains to be established. Here, we show that inhibitory avoidance in rats significantly increases the levels of autophagy and lysosomal degradation proteins, including BECN1/beclin 1, LC3-II, SQSTM1/p62 and LAMP1, as well as autophagic flux in the hippocampus. Moreover, pharmacological inhibition or targeted molecular disruption of the learning-induced autophagy impairs long-term memory, leaving short-term memory intact. The increase in autophagy proteins results from active translation of their mRNA and not from changes in their total mRNA levels. Additionally, the induction of autophagy requires the immediate early gene /. Finally, in contrast to classical regulation of autophagy in other systems, we found that the increase in autophagy upon learning is dispensable for the increase in protein synthesis. We conclude that coupling between learning-induced translation and autophagy, rather than translation , is an essential mechanism of long-term memory.

Abbreviations: AAV: adeno-associated virus; ARC/ARG3.1: activity regulated cytoskeletal-associated protein; ATG: autophagy related; DG: dentate gyrus; GFP: green fluorescent protein; IA: inhibitory avoidance; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; ODN: oligodeoxynucleotide; qPCR: quantitative polymerase chain reaction; SBI: SBI0206965; SQSTM1/p62: sequestosome 1; SUnSET: surface sensing of translation; TRAP: translating ribosome affinity purification; ULK1: unc-51 like kinase 1.
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http://dx.doi.org/10.1080/15548627.2020.1775393DOI Listing
June 2020

A role for CIM6P/IGF2 receptor in memory consolidation and enhancement.

Elife 2020 05 5;9. Epub 2020 May 5.

Center for Neural Science, New York University, New York, United States.

Cation-independent mannose-6-phosphate receptor, also called insulin-like growth factor two receptor (CIM6P/IGF2R), plays important roles in growth and development, but is also extensively expressed in the mature nervous system, particularly in the hippocampus, where its functions are largely unknown. One of its major ligands, IGF2, is critical for long-term memory formation and strengthening. Using CIM6P/IGF2R inhibition in rats and neuron-specific knockdown in mice, here we show that hippocampal CIM6P/IGF2R is necessary for hippocampus-dependent memory consolidation, but dispensable for learning, memory retrieval, and reconsolidation. CIM6P/IGF2R controls the training-induced upregulation of protein synthesis, including increase of Arc, Egr1, and c-Fos proteins, without affecting their mRNA induction. Hippocampal or systemic administration of mannose-6-phosphate, like IGF2, significantly enhances memory retention and persistence in a CIM6P/IGF2R-dependent manner. Thus, hippocampal CIM6P/IGF2R plays a critical role in memory consolidation by controlling the rate of training-regulated protein metabolism and is also a target mechanism for memory enhancement.
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http://dx.doi.org/10.7554/eLife.54781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7200152PMC
May 2020

Early life experiences selectively mature learning and memory abilities.

Nat Commun 2020 01 31;11(1):628. Epub 2020 Jan 31.

Center for Neural Science, New York University, New York, NY, 10003, USA.

The mechanisms underlying the maturation of learning and memory abilities are poorly understood. Here we show that episodic learning produces unique biological changes in the hippocampus of infant rats and mice compared to juveniles and adults. These changes include persistent neuronal activation, BDNF-dependent increase in the excitatory synapse markers synaptophysin and PSD-95, and significant maturation of AMPA receptor synaptic responses. Inhibition of PSD-95 induction following learning impairs both AMPA receptor response maturation and infantile memory, indicating that the synapse formation/maturation is necessary for creating infantile memories. Conversely, capturing the learning-induced changes by presenting a subsequent learning experience or by chemogenetic activation of the neural ensembles tagged by learning matures memory functional competence. This memory competence is selective for the type of experience encountered, as it transfers within similar hippocampus-dependent learning domains but not to other hippocampus-dependent types of learning. Thus, experiences in early life produce selective maturation of memory abilities.
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http://dx.doi.org/10.1038/s41467-020-14461-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6994621PMC
January 2020

Enhancing Executive Functions Through Social Interactions: Causal Evidence Using a Cross-Species Model.

Front Psychol 2019 19;10:2472. Epub 2019 Nov 19.

Department of Applied Psychology, New York University, New York, NY, United States.

It has long been theorized that humans develop higher mental functions, such as executive functions (EFs), within the context of interpersonal interactions and social relationships. Various components of social interactions, such as interpersonal communication, perspective taking, and conforming/adhering to social rules, may create important (and perhaps even necessary) opportunities for the acquisition and continued practice of EF skills. Furthermore, positive and stable relationships facilitate the development and maintenance of EFs across the lifespan. However, experimental studies investigating the extent to which social experiences contribute causally to the development of EFs are lacking. Here, we present experimental evidence that social experiences and the acquisition of social skills influence the development of EFs. Specifically, using a rat model, we demonstrate that following exposure to early-life adversity, a socialization intervention causally improves working memory in peri-adolescence. Our findings combined with the broader literature promote the importance of cultivating social skills in support of EF development and maintenance across the lifespan. Additionally, cross-species research will provide insight into causal mechanisms by which social experiences influence cognitive development and contribute to the development of biologically sensitive interventions.
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http://dx.doi.org/10.3389/fpsyg.2019.02472DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877690PMC
November 2019

Corticosterone administration targeting a hypo-reactive HPA axis rescues a socially-avoidant phenotype in scarcity-adversity reared rats.

Dev Cogn Neurosci 2019 12 17;40:100716. Epub 2019 Oct 17.

Emotional Brain Institute, Nathan Kline Institute & Department of Child and Adolescent Psychiatry, New York University School of Medicine, 1 Park Ave, New York, NY 10016, USA. Electronic address:

It is well-established that children from low-income, under-resourced families are at increased risk of altered social development. However, the biological mechanisms by which poverty-related adversities can "get under the skin" to influence social behavior are poorly understood and cannot be easily ascertained using human research alone. This study utilized a rodent model of "scarcity-adversity," which encompasses material resource deprivation (scarcity) and reduced caregiving quality (adversity), to explore how early-life scarcity-adversity causally influences social behavior via disruption of developing stress physiology. Results showed that early-life scarcity-adversity exposure increased social avoidance when offspring were tested in a social approach test in peri-adolescence. Furthermore, early-life scarcity-adversity led to blunted hypothalamic-pituitary-adrenal (HPA) axis activity as measured via adrenocorticotropic hormone (ACTH) and corticosterone (CORT) reactivity following the social approach test. Western blot analysis of brain tissue revealed that glucocorticoid receptor levels in the dorsal (but not ventral) hippocampus and medial prefrontal cortex were significantly elevated in scarcity-adversity reared rats following the social approach test. Finally, pharmacological repletion of CORT in scarcity-adversity reared peri-adolescents rescued social behavior. Our findings provide causal support that early-life scarcity-adversity exposure negatively impacts social development via a hypocorticosteronism-dependent mechanism, which can be targeted via CORT administration to rescue social behavior.
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http://dx.doi.org/10.1016/j.dcn.2019.100716DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6939642PMC
December 2019

Developmental changes in plasticity, synaptic, glia, and connectivity protein levels in rat basolateral amygdala.

Learn Mem 2019 11 15;26(11):436-448. Epub 2019 Oct 15.

Center for Neural Science, New York University, New York, New York 10003, USA.

The basolateral complex of amygdala (BLA) processes emotionally arousing aversive and rewarding experiences. The BLA is critical for acquisition and storage of threat-based memories and the modulation of the consolidation of arousing explicit memories, that is, the memories that are encoded and stored by the medial temporal lobe. In addition, in conjunction with the medial prefrontal cortex (mPFC), the BLA plays an important role in fear memory extinction. The BLA develops relatively early in life, but little is known about the molecular changes that accompany its development. Here, we quantified relative basal expression levels of sets of plasticity, synaptic, glia, and connectivity proteins in the rat BLA at various developmental ages: postnatal day 17 (PN17, infants), PN24 (juveniles), and PN80 (young adults). We found that the levels of activation markers of brain plasticity, including phosphorylation of CREB at Ser133, CamKIIα at Thr286, pERK1/pERK2 at Thr202/Tyr204, and GluA1 at Ser831 and Ser845, were significantly higher in infant and juvenile compared with adult brain. In contrast, age increase was accompanied by a significant augmentation in the levels of proteins that mark synaptogenesis and synapse maturation, such as synaptophysin, PSD95, SynCAM, GAD65, GAD67, and GluN2A/GluN2B ratio. Finally, we observed significant age-associated changes in structural markers, including MAP2, MBP, and MAG, suggesting that the structural connectivity of the BLA increases over time. The biological differences in the BLA between developmental ages compared with adulthood suggest the need for caution in extrapolating conclusions based on BLA-related brain plasticity and behavioral studies conducted at different developmental stages.
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http://dx.doi.org/10.1101/lm.049866.119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6796789PMC
November 2019

Wilm's tumor 1 promotes memory flexibility.

Nat Commun 2019 08 21;10(1):3756. Epub 2019 Aug 21.

Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, 10029, NY, USA.

Under physiological conditions, strength and persistence of memory must be regulated in order to produce behavioral flexibility. In fact, impairments in memory flexibility are associated with pathologies such as post-traumatic stress disorder or autism; however, the underlying mechanisms that enable memory flexibility are still poorly understood. Here, we identify transcriptional repressor Wilm's Tumor 1 (WT1) as a critical synaptic plasticity regulator that decreases memory strength, promoting memory flexibility. WT1 is activated in the hippocampus following induction of long-term potentiation (LTP) or learning. WT1 knockdown enhances CA1 neuronal excitability, LTP and long-term memory whereas its overexpression weakens memory retention. Moreover, forebrain WT1-deficient mice show deficits in both reversal, sequential learning tasks and contextual fear extinction, exhibiting impaired memory flexibility. We conclude that WT1 limits memory strength or promotes memory weakening, thus enabling memory flexibility, a process that is critical for learning from new experiences.
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http://dx.doi.org/10.1038/s41467-019-11781-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6704057PMC
August 2019

Lactate from astrocytes fuels learning-induced mRNA translation in excitatory and inhibitory neurons.

Commun Biol 2019 2;2:247. Epub 2019 Jul 2.

1Center for Neural Science, New York University, New York, NY 10003 USA.

Glycogenolysis and lactate transport from astrocytes to neurons is required for long-term memory formation, but the role of this lactate is poorly understood. Here we show that the Krebs cycle substrates pyruvate and ketone body B3HB can functionally replace lactate in rescuing memory impairment caused by inhibition of glycogenolysis or expression knockdown of glia monocarboxylate transporters (MCTs) 1 and 4 in the dorsal hippocampus of rats. In contrast, either metabolite is unable to rescue memory impairment produced by expression knockdown of MCT2, which is selectively expressed by neurons, indicating that a critical role of astrocytic lactate is to provide energy for neuronal responses required for long-term memory. These responses include learning-induced mRNA translation in both excitatory and inhibitory neurons, as well as expression of Arc/Arg3.1. Thus, astrocytic lactate acts as an energy substrate to fuel learning-induced de novo neuronal translation critical for long-term memory.
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http://dx.doi.org/10.1038/s42003-019-0495-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6606643PMC
May 2020

Developmental changes in plasticity, synaptic, glia, and connectivity protein levels in rat medial prefrontal cortex.

Learn Mem 2018 10 17;25(10):533-543. Epub 2018 Sep 17.

Center for Neural Science, New York University, New York, New York 10003, USA.

The medial prefrontal cortex (mPFC) plays a critical role in complex brain functions including decision-making, integration of emotional, and cognitive aspects in memory processing and memory consolidation. Because relatively little is known about the molecular mechanisms underlying its development, we quantified rat mPFC basal expression levels of sets of plasticity, synaptic, glia, and connectivity proteins at different developmental ages. Specifically, we compared the mPFC of rats at postnatal day 17 (PN17), when they are still unable to express long-term contextual and spatial memories, to rat mPFC at PN24, when they have acquired the ability of long-term memory expression and finally to the mPFC of adult rats. We found that, with increased age, there are remarkable and significant decreases in markers of cell activation and significant increases in proteins that mark synaptogenesis and synapse maturation. Furthermore, we found significant changes in structural markers over the ages, suggesting that structural connectivity of the mPFC increases over time. Finally, the substantial biological difference in mPFC at different ages suggest caution in extrapolating conclusions from brain plasticity studies conducted at different developmental stages.
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http://dx.doi.org/10.1101/lm.047753.118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6149953PMC
October 2018

Mechanisms of critical period in the hippocampus underlie object location learning and memory in infant rats.

Learn Mem 2018 04 15;25(4):176-182. Epub 2018 Mar 15.

Center for Neural Science, New York University, New York, New York 10003, USA.

Episodic memories in early childhood are rapidly forgotten, a phenomenon that is associated with "infantile amnesia," the inability of adults to remember early-life experiences. We recently showed that early aversive contextual memory in infant rats, which is in fact rapidly forgotten, is actually not lost, as reminders presented later in life reinstate a long-lasting and context-specific memory. We also showed that the formation of this infantile memory recruits in the hippocampus mechanisms typical of developmental critical periods. Here, we tested whether similar mechanisms apply to a nonaversive, hippocampal type of learning. We report that novel object location (nOL) learned at postnatal day 17 (PN17) undergoes the typical rapid forgetting of infantile learning. However, a later reminder reinstates memory expression. Furthermore, as for aversive experiences, nOL learning at PN17 engages critical period mechanisms in the dorsal hippocampus: it induces a switch in the GluN2A/2B-NMDA receptor ratio, and brain-derived neurotrophic factor injected bilaterally into the dorsal hippocampus immediately after training results in long-lasting memory expression. We conclude that in infancy the hippocampus plays a necessary role in processing episodic and contextual memories, including nonaversive ones, and matures through a developmental critical period.
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http://dx.doi.org/10.1101/lm.046946.117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5855526PMC
April 2018

NLGN1 and NLGN2 in the prefrontal cortex: their role in memory consolidation and strengthening.

Curr Opin Neurobiol 2018 02 23;48:122-130. Epub 2017 Dec 23.

Center for Neural Science, New York University, New York, NY 10003, USA. Electronic address:

The prefrontal cortex (PFC) is critical for memory formation, but the underlying molecular mechanisms are poorly understood. Clinical and animal model studies have shown that changes in PFC excitation and inhibition are important for cognitive functions as well as related disorders. Here, we discuss recent findings revealing the roles of the excitatory and inhibitory synaptic proteins neuroligin 1 (NLGN1) and NLGN2 in the PFC in memory formation and modulation of memory strength. We propose that shifts in NLGN1 and NLGN2 expression in specific excitatory and inhibitory neuronal subpopulations in response to experience regulate the dynamic processes of memory consolidation and strengthening. Because excitatory/inhibitory imbalances accompany neuropsychiatric disorders in which strength and flexibility of representations play important roles, understanding these mechanisms may suggest novel therapies.
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http://dx.doi.org/10.1016/j.conb.2017.12.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5825275PMC
February 2018

Insulin-Like Growth Factor II Targets the mTOR Pathway to Reverse Autism-Like Phenotypes in Mice.

J Neurosci 2018 01 7;38(4):1015-1029. Epub 2017 Dec 7.

Center for Neural Science, New York University, New York, New York, 10003

Autism spectrum disorder (ASD) is a developmental disability characterized by impairments in social interaction and repetitive behavior, and is also associated with cognitive deficits. There is no current treatment that can ameliorate most of the ASD symptomatology; thus, identifying novel therapies is urgently needed. We used male BTBR /J (BTBR) mice, a model that reproduces most of the core behavioral phenotypes of ASD, to test the effects of systemic administration of insulin-like growth factor II (IGF-II), a polypeptide that crosses the blood-brain barrier and acts as a cognitive enhancer. We show that systemic IGF-II treatments reverse the typical defects in social interaction, cognitive/executive functions, and repetitive behaviors reflective of ASD-like phenotypes. In BTBR mice, IGF-II, via IGF-II receptor, but not via IGF-I receptor, reverses the abnormal levels of the AMPK-mTOR-S6K pathway and of active translation at synapses. Thus, IGF-II may represent a novel potential therapy for ASD. Currently, there is no effective treatment for autism spectrum disorder (ASD), a developmental disability affecting a high number of children. Using a mouse model that expresses most of the key core as well as associated behavioral deficits of ASD, that are, social, cognitive, and repetitive behaviors, we report that a systemic administration of the polypeptide insulin-like growth factor II (IGF-II) reverses all these deficits. The effects of IGF-II occur via IGF-II receptors, and not IGF-I receptors, and target both basal and learning-dependent molecular abnormalities found in several ASD mice models, including those of identified genetic mutations. We suggest that IGF-II represents a potential novel therapeutic target for ASD.
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http://dx.doi.org/10.1523/JNEUROSCI.2010-17.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5783959PMC
January 2018

Astrocyte glycogen and lactate: New insights into learning and memory mechanisms.

Glia 2018 06 27;66(6):1244-1262. Epub 2017 Oct 27.

Center for Neural Science, New York University, New York, New York, 10003.

Memory, the ability to retain learned information, is necessary for survival. Thus far, molecular and cellular investigations of memory formation and storage have mainly focused on neuronal mechanisms. In addition to neurons, however, the brain comprises other types of cells and systems, including glia and vasculature. Accordingly, recent experimental work has begun to ask questions about the roles of non-neuronal cells in memory formation. These studies provide evidence that all types of glial cells (astrocytes, oligodendrocytes, and microglia) make important contributions to the processing of encoded information and storing memories. In this review, we summarize and discuss recent findings on the critical role of astrocytes as providers of energy for the long-lasting neuronal changes that are necessary for long-term memory formation. We focus on three main findings: first, the role of glucose metabolism and the learning- and activity-dependent metabolic coupling between astrocytes and neurons in the service of long-term memory formation; second, the role of astrocytic glucose metabolism in arousal, a state that contributes to the formation of very long-lasting and detailed memories; and finally, in light of the high energy demands of the brain during early development, we will discuss the possible role of astrocytic and neuronal glucose metabolisms in the formation of early-life memories. We conclude by proposing future directions and discussing the implications of these findings for brain health and disease. Astrocyte glycogenolysis and lactate play a critical role in memory formation. Emotionally salient experiences form strong memories by recruiting astrocytic β2 adrenergic receptors and astrocyte-generated lactate. Glycogenolysis and astrocyte-neuron metabolic coupling may also play critical roles in memory formation during development, when the energy requirements of brain metabolism are at their peak.
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http://dx.doi.org/10.1002/glia.23250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5903986PMC
June 2018

Infantile Amnesia: A Critical Period of Learning to Learn and Remember.

J Neurosci 2017 06;37(24):5783-5795

Center for Neural Science, New York University, New York, New York 10003.

Infantile amnesia, the inability of adults to recollect early episodic memories, is associated with the rapid forgetting that occurs in childhood. It has been suggested that infantile amnesia is due to the underdevelopment of the infant brain, which would preclude memory consolidation, or to deficits in memory retrieval. Although early memories are inaccessible to adults, early-life events, such as neglect or aversive experiences, can greatly impact adult behavior and may predispose individuals to various psychopathologies. It remains unclear how a brain that rapidly forgets, or is not yet able to form long-term memories, can exert such a long-lasting and important influence. Here, with a particular focus on the hippocampal memory system, we review the literature and discuss new evidence obtained in rats that illuminates the paradox of infantile amnesia. We propose that infantile amnesia reflects a developmental critical period during which the learning system is learning how to learn and remember.
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http://dx.doi.org/10.1523/JNEUROSCI.0324-17.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5473198PMC
June 2017

Computational model of a positive BDNF feedback loop in hippocampal neurons following inhibitory avoidance training.

Learn Mem 2016 12 15;23(12):714-722. Epub 2016 Nov 15.

Department of Neurobiology and Anatomy, McGovern Medical School, Houston, Texas 77030, USA

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). Increased levels of C/EBPβ lead to increased bdnf expression. Simulations predicted that an empirically observed delay in the BDNF-pCREB-C/EBPβ feedback loop has a profound effect on the dynamics of consolidation. The model also predicted that at least two independent self-sustaining signaling pathways downstream from the BDNF-pCREB-C/EBPβ feedback loop contribute to consolidation. Currently, the nature of these downstream pathways is unknown.
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http://dx.doi.org/10.1101/lm.042044.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110990PMC
December 2016

Direct dorsal hippocampal-prelimbic cortex connections strengthen fear memories.

Nat Neurosci 2017 01 21;20(1):52-61. Epub 2016 Nov 21.

Center for Neural Science, New York University, New York, New York, USA.

The ability to regulate the consolidation and strengthening of memories for threatening experiences is critical for mental health, and its dysregulation may lead to psychopathologies. Re-exposure to the context in which the threat was experienced can either increase or decrease fear response through distinct processes known, respectively, as reconsolidation or extinction. Using a context retrieval-dependent memory-enhancement model in rats, we report that memory strengthens through activation of direct projections from dorsal hippocampus to prelimbic (PL) cortex and activation of critical PL molecular mechanisms that are not required for extinction. Furthermore, while sustained PL brain-derived neurotrophic factor (BDNF) expression is required for memory consolidation, retrieval engages PL BDNF to regulate excitatory and inhibitory synaptic proteins neuroligin 1 and neuroligin 2, which promote memory strengthening while inhibiting extinction. Thus, context retrieval-mediated fear-memory enhancement results from a concerted action of mechanisms that strengthen memory through reconsolidation while suppressing extinction.
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http://dx.doi.org/10.1038/nn.4443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5191950PMC
January 2017

Developmental changes in plasticity, synaptic, glia and connectivity protein levels in rat dorsal hippocampus.

Neurobiol Learn Mem 2016 Nov 12;135:125-138. Epub 2016 Aug 12.

Center for Neural Science, New York University, New York, 10003 NY, USA. Electronic address:

Thus far the identification and functional characterization of the molecular mechanisms underlying synaptic plasticity, learning, and memory have not been particularly dissociated from the contribution of developmental changes. Brain plasticity mechanisms have been largely identified and studied using in vitro systems mainly derived from early developmental ages, yet they are considered to be general plasticity mechanisms underlying functions -such as long-term memory- that occurs in the adult brain. Although it is possible that part of the plasticity mechanisms recruited during development is then re-recruited in plasticity responses in adulthood, systematic investigations about whether and how activity-dependent molecular responses differ over development are sparse. Notably, hippocampal-dependent memories are expressed relatively late in development, and the hippocampus undergoes and extended developmental post-natal structural and functional maturation, suggesting that the molecular mechanisms underlying hippocampal neuroplasticity may actually significantly change over development. Here we quantified the relative basal expression levels of sets of plasticity, synaptic, glia and connectivity proteins in rat dorsal hippocampus, a region that is critical for the formation of long-term explicit memories, at two developmental ages, postnatal day 17 (PN17) and PN24, which correspond to a period of relative functional immaturity and maturity, respectively, and compared them to adult age. We found that the levels of numerous proteins and/or their phosphorylation, known to be critical for synaptic plasticity underlying memory formation, including immediate early genes (IEGs), kinases, transcription factors and AMPA receptor subunits, peak at PN17 when the hippocampus is not yet able to express long-term memory. It remains to be established if these changes result from developmental basal activity or infantile learning. Conversely, among all markers investigated, the phosphorylation of calcium calmodulin kinase II α (CamKII α and of extracellular signal-regulated kinases 2 (ERK-2), and the levels of GluA1 and GluA2 significantly increase from PN17 to PN24 and then remain similar in adulthood, thus representing correlates paralleling long-term memory expression ability.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5050161PMC
http://dx.doi.org/10.1016/j.nlm.2016.08.005DOI Listing
November 2016

Infantile amnesia reflects a developmental critical period for hippocampal learning.

Nat Neurosci 2016 09 18;19(9):1225-33. Epub 2016 Jul 18.

Center for Neural Science, New York University, New York, New York, USA.

Episodic memories formed during the first postnatal period are rapidly forgotten, a phenomenon known as 'infantile amnesia'. In spite of this memory loss, early experiences influence adult behavior, raising the question of which mechanisms underlie infantile memories and amnesia. Here we show that in rats an experience learned during the infantile amnesia period is stored as a latent memory trace for a long time; indeed, a later reminder reinstates a robust, context-specific and long-lasting memory. The formation and storage of this latent memory requires the hippocampus, follows a sharp temporal boundary and occurs through mechanisms typical of developmental critical periods, including the expression switch of the NMDA receptor subunits from 2B to 2A, which is dependent on brain-derived neurotrophic factor (BDNF) and metabotropic glutamate receptor 5 (mGluR5). Activating BDNF or mGluR5 after training rescues the infantile amnesia. Thus, early episodic memories are not lost but remain stored long term. These data suggest that the hippocampus undergoes a developmental critical period to become functionally competent.
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http://dx.doi.org/10.1038/nn.4348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5003643PMC
September 2016

Astrocytic β2-adrenergic receptors mediate hippocampal long-term memory consolidation.

Proc Natl Acad Sci U S A 2016 07 8;113(30):8526-31. Epub 2016 Jul 8.

Center for Neural Science, New York University, New York, NY 10003;

Emotionally relevant experiences form strong and long-lasting memories by critically engaging the stress hormone/neurotransmitter noradrenaline, which mediates and modulates the consolidation of these memories. Noradrenaline acts through adrenergic receptors (ARs), of which β2-adrenergic receptors (βARs) are of particular importance. The differential anatomical and cellular distribution of βAR subtypes in the brain suggests that they play distinct roles in memory processing, although much about their specific contributions and mechanisms of action remains to be understood. Here we show that astrocytic rather than neuronal β2ARs in the hippocampus play a key role in the consolidation of a fear-based contextual memory. These hippocampal β2ARs, but not β1ARs, are coupled to the training-dependent release of lactate from astrocytes, which is necessary for long-term memory formation and for underlying molecular changes. This key metabolic role of astrocytic β2ARs may represent a novel target mechanism for stress-related psychopathologies and neurodegeneration.
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http://dx.doi.org/10.1073/pnas.1605063113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4968707PMC
July 2016

Insulin-like growth factor 2 rescues aging-related memory loss in rats.

Neurobiol Aging 2016 08 21;44:9-21. Epub 2016 Apr 21.

Center for Neural Science, New York University, New York, NY, USA. Electronic address:

Aging is accompanied by declines in memory performance, and particularly affects memories that rely on hippocampal-cortical systems, such as episodic and explicit. With aged populations significantly increasing, the need for preventing or rescuing memory deficits is pressing. However, effective treatments are lacking. Here, we show that the level of the mature form of insulin-like growth factor 2 (IGF-2), a peptide regulated in the hippocampus by learning, required for memory consolidation and a promoter of memory enhancement in young adult rodents, is significantly reduced in hippocampal synapses of aged rats. By contrast, the hippocampal level of the immature form proIGF-2 is increased, suggesting an aging-related deficit in IGF-2 processing. In agreement, aged compared to young adult rats are deficient in the activity of proprotein convertase 2, an enzyme that likely mediates IGF-2 posttranslational processing. Hippocampal administration of the recombinant, mature form of IGF-2 rescues hippocampal-dependent memory deficits and working memory impairment in aged rats. Thus, IGF-2 may represent a novel therapeutic avenue for preventing or reversing aging-related cognitive impairments.
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http://dx.doi.org/10.1016/j.neurobiolaging.2016.04.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4913033PMC
August 2016

Effective anti-Alzheimer Aβ therapy involves depletion of specific Aβ oligomer subtypes.

Neurol Neuroimmunol Neuroinflamm 2016 Jun 10;3(3):e237. Epub 2016 May 10.

Departments of Psychiatry (E.M.K., S.H.K., J.C.K., A.L., S.G., J.W.S.), Neurology (E.M.K., S.H.K., J.C.K., A.L., M.E., S.G., J.W.S.), and Pediatrics (M.E.), and Alzheimer's Disease Research Center (E.M.K., S.H.K., J.C.K., A.L., M.E., S.G., J.W.S.), Icahn School of Medicine at Mount Sinai, New York, NY; Department of Molecular Biology and Biochemistry (A.H., R.A., C.G.G.), University of California at Irvine; King Fahd Medical Research Center (A.H., R.A., C.G.G.), KAU, Jeddah, Saudi Arabia; Department of Biochemistry (A.S.), Faculty of Medicine, Graduate School of Medicine & Pharmaceutical Sciences, University of Toyama, Japan; Center for Neural Science (C.M.A.), New York University, NY; Northwestern University (W.L.K.), Chicago, IL; Department of Neurology and Brain Mind Research Institute (P.S., N.R.R.), Weill Cornell Medical College, New York, NY; Biochemistry Department (C.G.G.), Faculty of Science and Experimental Biochemistry Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia; James J. Peters VA Medical Center (S.G.), Bronx, NY; and Sanford Consortium for Regenerative Medicine (J.W.S.), University of California San Diego, La Jolla, CA.

Background: Recent studies have implicated specific assembly subtypes of β-amyloid (Aβ) peptide, specifically soluble oligomers (soAβ) as disease-relevant structures that may underlie memory loss in Alzheimer disease. Removing existing soluble and insoluble Aβ assemblies is thought to be essential for any attempt at stabilizing brain function and slowing cognitive decline in Alzheimer disease. IV immunoglobulin (IVIg) therapies have been shown to contain naturally occurring polyclonal antibodies that recognize conformational neoepitopes of soluble or insoluble Aβ assemblies including soAβ. These naturally occurring polyclonal antibodies have been suggested to underlie the apparent clinical benefits of IVIg. However, direct evidence linking anti-Aβ antibodies to the clinical bioactivity of IVIg has been lacking.

Methods: Five-month-old female Dutch APP E693Q mice were treated for 3 months with neat IVIg or with IVIg that had been affinity-depleted over immobilized Aβ conformers in 1 of 2 assembly states. Memory was assessed in a battery of tests followed by quantification of brain soAβ levels using standard anti-soAβ antibodies.

Results: We provide evidence that NU4-type soAβ (NU4-soAβ) assemblies accumulate in the brains of Dutch APP E693Q mice and are associated with defects in memory, even in the absence of insoluble Aβ plaques. Memory benefits were associated with depletion from APP E693Q mouse brain of NU4-soAβ and A11-soAβ but not OC-type fibrillar Aβ oligomers.

Conclusions: We propose that targeting of specific soAβ assembly subtypes may be an important consideration in the therapeutic and/or prophylactic benefit of anti-Aβ antibody drugs.
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http://dx.doi.org/10.1212/NXI.0000000000000237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4864617PMC
June 2016

The Role of Lactate-Mediated Metabolic Coupling between Astrocytes and Neurons in Long-Term Memory Formation.

Front Integr Neurosci 2016 3;10:10. Epub 2016 Mar 3.

Center for Neural Science, New York University New York, NY, USA.

Long-term memory formation, the ability to retain information over time about an experience, is a complex function that affects multiple behaviors, and is an integral part of an individual's identity. In the last 50 years many scientists have focused their work on understanding the biological mechanisms underlying memory formation and processing. Molecular studies over the last three decades have mostly investigated, or given attention to, neuronal mechanisms. However, the brain is composed of different cell types that, by concerted actions, cooperate to mediate brain functions. Here, we consider some new insights that emerged from recent studies implicating astrocytic glycogen and glucose metabolisms, and particularly their coupling to neuronal functions via lactate, as an essential mechanism for long-term memory formation.
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http://dx.doi.org/10.3389/fnint.2016.00010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4776217PMC
March 2016

From Memory Impairment to Posttraumatic Stress Disorder-Like Phenotypes: The Critical Role of an Unpredictable Second Traumatic Experience.

J Neurosci 2015 Dec;35(48):15903-15

Center for Neural Science, New York University, New York, New York 10003

Arousal and stress critically regulate memory formation and retention. Increasing levels of stress produce an inverted U-shaped effect on cognitive performance, including the retention of explicit memories, and experiencing a severe stress during a traumatic event may lead to posttraumatic stress disorder (PTSD). The molecular mechanisms underlying the impairing effect of a severe stress on memory and the key contribution of traumatic experiences toward the development of PTSD are still unknown. Here, using increasing footshock intensities in an inhibitory avoidance paradigm, we reproduced the inverted U-shaped curve of memory performance in rats. We then show that the inverted U profile of memory performance correlates with an inverted U profile of corticosterone level in the circulation and of brain-derived neurotrophic factor, phosphorylated tropomyosin-receptor kinase B, and methyl CpG binding protein in the dorsal hippocampus. Furthermore, training with the highest footshock intensity (traumatic experience) led to a significant elevation of hippocampal glucocorticoid receptors. Exposure to an unpredictable, but not to a predictable, highly stressful reminder shock after a first traumatic experience resulted in PTSD-like phenotypes, including increased memory of the trauma, high anxiety, threat generalization, and resistance to extinction. Systemic corticosterone injection immediately after the traumatic experience, but not 3 d later, was sufficient to produce PTSD-like phenotypes. We suggest that, although after a first traumatic experience a suppression of the corticosterone-dependent response protects against the development of an anxiety disorder, experiencing more than one trauma (multiple hits) is a critical contributor to the etiology of PTSD.
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http://dx.doi.org/10.1523/JNEUROSCI.0771-15.2015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4666915PMC
December 2015

Insulin Like Growth Factor 2 Expression in the Rat Brain Both in Basal Condition and following Learning Predominantly Derives from the Maternal Allele.

PLoS One 2015 23;10(10):e0141078. Epub 2015 Oct 23.

Center for Neural Science, New York University, New York, NY, 10003, United States of America.

Insulin like growth factor 2 (Igf2) is known as a maternally imprinted gene involved in growth and development. Recently, Igf2 was found to also be regulated and required in the adult rat hippocampus for long-term memory formation, raising the question of its allelic regulation in adult brain regions following experience and in cognitive processes. We show that, in adult rats, Igf2 is abundantly expressed in brain regions involved in cognitive functions, like hippocampus and prefrontal cortex, compared to the peripheral tissues. In contrast to its maternal imprinting in peripheral tissues, Igf2 is mainly expressed from the maternal allele in these brain regions. The training-dependent increase in Igf2 expression derives proportionally from both parental alleles, and, hence, is mostly maternal. Thus, Igf2 parental expression in the adult rat brain does not follow the imprinting rules found in peripheral tissues, suggesting differential expression regulation and functions of imprinted genes in the brain.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0141078PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4619677PMC
June 2016