Michela Gallagher - US grants

It is well documented that opiate and opioid peptide manipulations alter memory processes in young adult animals. In these investigations it has been consistently reported that post-training opiate antagonist administration enhances retention. The proposed research is aimed at investigating the role of opioid peptide function in memory processes in aged animals. The experiments are designed initially to examine whether age-related declines in learning/memory performance are sensitive to opiate treatments. Using spatial learning tasks which are sensitive to aging in rats, Part I of this proposal will examine the effects of post-training opiate antagonist treatments in young adult and aged rats on memory of spatial learning using the radial-arm maze. In Part II, experiments will be conducted to assess whether the medial septal area (MSA) is sensitive to the effects of opiate manipulations on spatial memory. Cholinergic neurons located in the MSA which project to the hippocampus have been demonstrated to be regulated by opiate receptor mechanisms. This cholinergic input to the hippocampus has been implicated in spatial learning in young animals and also appears to undergo an age-related functional decline which parallels the emergence of spatial learning deficits in rats. Finally, Part III of this proposal will examine whether treatments which alter the performance of young and aged animals on spatial learning tasks produce concomitant changes in place coding of neural units within the hippocampus. The results of this research will indicate whether the age-related decline in performance of spatial learning in old rats is (1) sensitive to treatments which improve memory for spatial learning in young animals; (2) sensitive to opiate manipulation at a brain site (MSA) which provides important input to the hippocampus; and (3) whether hippocampal neural correlates of the impaired spatial learning in old animals are altered by treatments which may improve maze performance. An understanding of the neural mechanisms underlying the effects of opiate manipulations on memory, particularly in aged animals, may have important clinical implications in light of recent reports that opiate antagonist administration benefits some patients with Alzheimer's disease.

This request for an ADAMHA RSDA is intended to facilitate the career developmenbt of a scientist whose research is focusedin the are of brain mechanisms underlying learning and memory. Previous research has implicated opioid peptide and norepinephrine (NE) systems in learning and memory processes. More specifically, the results of many studies which have assessed the effects of post-conditioning manipulations of opiate and NE activity have indicated that opiate and NE systems appear to exert opposing effects on retention of conditioning. Through the use of intracranial pharmacological injecton techniques, we have observed that at least a component of the opiate sensitive and NE systems which affect mamory processes appear to be located within the amygdala complex. More recently, we have provided evidence that manipulations of opiate and NE activity within the central nucleus region of the amygdala complex produce effects on the acquisition of classically conditioned heart rate in rabbits which closely parallel the effects of these same manipulations on retention of conditioning in rats. Basedon other lines of research which have provided evidence that opiate sensitive mechanisms located in the soma/dendritic and terminal fields of NE neurons are capable of alteraing brain NE function, the proposed research is designed to test the hypothesis that opiate sensitive mechanisms may alter learning and memory by regulating NE systems. To this end we propose to examine the effects of opiate manipulations on learning and memory in animals with selective NE system lesions. In addition, the possible contribution of vasopressin activity within the amygdala to these behavioral functions will also be examined. The behavioral testing procedures which will be used are those which wer have previously found to be sensitive to independent manipulation of opiate and NE activity within the amygdala. These are passive avoidance conditioning in rats, and classical conditioning of heart rate responding in rabbits. In addition to the proposed experiments, the applicant has included plans for research and professional development which involve collaboration and training with colleagues in both the Psychology Department and the Neurobiology Program at UNC, Chapel Hill.

Opiate manipulations in the amygdala complex alter learning and memory processes when aversive conditioning tasks are used. Current research in our laboratory is examining opiate/norepinephrine (NE) interactions in the regulation of learning and memory of aversive conditioning. At the same time, numerous investigations have reported that systemic opiate agonist and antagonist administration can alter memory using a variety of tasks which employ aversive, appetitive and non-reinforced exposure to stimuli. A major goal of the proposed research will be to explore neural systems and mechanisms which may underlie the effects of opiate treatment on memory for non-aversive experiences. The behavioral tasks which have been recently employed in our laboratory include: 1) a latent inhibition paradigm in which retention of CS pre-exposure is assessed on subsequent classical conditioning of heart rate responses in rabbits and 2) a food-rewarded spatial learning task using rats. The results of our preliminary studies indicate that in both of these tasks post-training systemic administration of an opiate antagonist enhances retention, an effect which parallels that obtained using aversive conditioning procedures. In the proposed experiments, the amygdala complex and the hippocampal formation will be explored as possible target sites for the effects of opiates on memory when these non-aversive tasks are used. In addition we propose to investigate whether the effects of opiate manipulation on memory using these tasks are dependent on intact NE function in the brain. These experiments should provide important new information regarding the distribution and function of brain opioid peptides which regulate memory processes. Other experiments in this proposal are included to develop an in vitro amygdala slice preparation from rabbit brain which will include the central nucleus and several of its inputs. The central nucleus appears to be a critical component of the neural circuitry which underlies the acquisition of classically conditioned heart rate in the rabbit. This in vitro preparation may provide a valuable tool for investigating synaptic processing in this region which may lead to new insights into neural mechanisms involved in learning and memory.

This research program maintains a focus on the regulation of learning and memory by opioid peptides within the amygdala complex and other related limbic system structures. Behavioral experiments are designed to examine functional similarities between opioid peptides that regulate memory processes and those involved in attention. Testing procedures, i.e. overshadowing; conditioned inhibition, will be used to evaluate whether the effects of pretraining and/or posttraining opiate antagonist treatment are sensitive to manipulating the saliency and/or relevance of cues within a task. Although previous independent lines of investigation have implicated opioid peptides in memory and attention, evidence for a common functional substrate of opioid peptides that regulate the allocation of processing and the preservation information may emerge from these investigations. In order to define the CNS components of opioid peptides that contribute to learning and memory, experiments will examine interactions of opioid peptides with ascending norepinephrine (NE) and basal forebrain cholinergic systems. Experiments with a focus on the septal region and upon septo-hippocampal cholinergic function will complement ongoing research aimed at the amygdala central nucleus where opiate/NE interactions have been implicated in memory function. Finally, research is proposed to further investigate in selected limbic structures the identify of opioid peptides that provide a substrate for the effects of opiate manipulations on learning and memory. Brain systems that are the target of our research, i.e. amygdala, septal region, hippocampus, possess multiple distinct opioid peptide systems. Behavioral tasks, previously identified as sensitive to intracranial manipulations of opioid peptide function at these sites, will be used to determine the conditions that regulate activity in these hererogeneous opioid peptide systems. The content of multiple opioid peptides will be monitored by radioimmunoassays within targeted structures in response selected behavioral manipulations. This work provides an initial step toward characterizing the dynamic function of opioid peptide systems that contribute to learning and memory. The neuroanatomical/neurochemical systems examined in this research are central to understanding normal memory function as well as clinical syndromes characterized by a deterioration of memory.

A functional decline in the basal forebrain cholinergic (ACh) system may underly the mild/moderate changes in cognitive and memory capacity associated with normal aging. One aim of the proposed research is to assess the effects of normal aging in laboratory rodents on the basal forebrain ACh system, with special reference to the function of septo-hippocampal ACh neurons. Our prior work, as well as the results of other studies, suggest that the complement of basal forebrain ACh neurons is largely intact in the aged rodent brain as indicated by cell number, measurement of choline acetyltransferase (ChAT) and high-affinity choline uptake (HACU) in its basal state. This provides an interesting background for our recent observation that the dynamic response of hippocampal and cortical HACU to a behavioral manipulation is blunted in the aged brain. In order to further examine this phenomenon, training procedures that are normally sensitive to ACh manipulation and hippocampal damage in young rats, and that distinguish the behavioral impairments of aged rats, i.e., spatial learning, will be used. Initially, HACU and (3H)- hemicholinium-3 binding in synaptosomal preparations will be examined as markers for ACh neurons. Each of these measures manifests rapid regulation to manipulations of ACh neuronal activity in young animals. Subsequent experiments are designed to determine the neuroanatomical distribution of training-induced regulation of (3H)-hemicholinium binding using in vitro autoradiographic techniques. Another goal of this project is assess the extent to which different behavioral/neurobiological markers of aging are intercorrelated. To this end, behavioral data will be obtained for young and aged rats on a series of behavioral tasks that are selected to assess different functions (learning and memory, motor competence, etc.). Subsequently, analysis of a variety of targeted neurobiological markers in forebrain systems (limbic/cortical and striatum) will be assessed. The results should indicate 1) whether age-related changes in different behavioral functions occur somewhat independently, 2) whether distinctive neurobiological markers coincide with different indices of functional decline in the aged animal, and 3) importantly, in the context of our interest in cognitive/memory functions, whether a limited set of those neurobiological markers that change with age are specifically associated with the decline in spatial learning capacity in aged rats.

Studies of learning and memory are often performed using young adult animals as laboratory models of human learning. These investigations, however, do not address one of the major factors influencing memory: Aging. Dr. Gallagher's research focuses on providing a more complete description of learning ability in animals toward the end of their normal lifespan. Rodents are the ideal subjects in which to study age-related memory changes, because we can observe mild-to-severe memory impairments over the relatively short period (in human terms) of two to three years. In her previous work, Dr. Gallagher has developed a series of memory tests which clearly expose performance differences between young and aged animals. These tests, furthermore, are capable of distinguishing those behaviors which depend upon the integrity of certain identified brain regions, and those which do not. Dr. Gallagher will conduct several experiments to extend these findings, and will begin examining the extent to which each of these behavioral tasks depends upon a specific neurotransmitter system (acetylcholine) being intact. Specifically, she will determine the relationship between changes in behavioral capacities and the effects of training on acetylcholine function in aged animals. These results will address the hypothesis that altered learning and memory function in normal aging animals is associated with a change in the functional status of the basal forebrain cholinergic system. Knowledge about relationships between learning and memory and the status of a specific brain system during aging will provide a more complete understanding of progressive memorial deficits occurring over the lifespan.

Behavioral and neuropharmacological methods will be used to examine two notable features of organization within the limbic system. The first focus is on a set of structures recently referred to as the "extended amygdala", a system that includes the central nucleus of the amygdala, the sublenticular substantia innominata, the lateral bed nucleus of the stria terminalis and medial accumbens nucleus. The proposed work will examine the concept that this system allocates processing based on the learned significance of events. This cognitive view will be distinguished from the more traditional concept that components of this system are important for acquiring motivationally-determined associations, by which conditioned stimuli acquire either rewarding or aversive properties. Opioid peptide function in the extended amygdala will be examined within this framework. The second focus is on a system of prominent projections from the hippocampal formation and basolateral complex of the amygdala (ABL) that innervate the extended amygdala. Damage to either the hippocampal formation or ABL spares simple associative teaming, but these limbic structures are critical for more complex associative processes that can be studied in classical conditioning paradigms. The ABL will serve as a focus for examining its role in cross modal sensory/sensory associations and for determining the contribution of a N-methyl-D-aspartate mechanism to this form of learning. Then experiments are proposed to determine whether specific associative processes, that are dependent on the ABL and hippocampal formation, are implemented by their projections to the extended amygdala. These experiments are based on a model by which limbic inputs to the extended amygdala are gated by dopaminergic innervation from the ventral tegmentum. We will determine whether neurotoxic lesions that remove limbic inputs result in a selective loss of D2 binding in the extended amygdala. Then we will assess whether D2, but not D1, agonists microinjected into the extended amygdala selectively disrupt associative processes that depend on the integrity of the hippocampal formation and the ABL.

? DESCRIPTION (provided by applicant): This research program represents a multidisciplinary, integrated approach to understanding the effects of normal aging on a critical brain system that supports cognitive functions affected in humans as they age. We focus on brain aging in hippocampal/cortical circuits using male Long Evans rats, an outbred strain that exhibits individual differences in aging outcomes in well-characterized cognitive assessments. At older ages (24-28 month) cognitive impairment affects 50-60% of healthy rats in this population, while the remaining aged cohorts fall within the range of young adults (4-6 months). Research under this mechanism of support has identified alterations in the brain that are tightly coupled to these cognitive outcomes. Significant progress in the most recent funding period occurred in the use of experimental interventions to demonstrate the functional significance of altered network properties in circuitry comprised of the entorhinal cortex and its targets in the dentate gyrus (DG) and CA3 regions of the hippocampus. That research in the aged rodent model led to the successful use of a treatment in a proof-of-concept (POC) clinical study in elderly patients with amnestic mild cognitive impairment. Our proposed plans will build on our achievements, exploiting recent findings to embark on new lines of investigation to understand neurocognitive aging and modify aging outcomes. To that end, three Cores (Administrative, Animal Resource, and Bioinformatics/Data Management) will serve all of the participating investigators conducting research in three proposed projects. Proposed studies will build on an emerging consensus that the hippocampus integrates inputs from two interconnected, but anatomically distinct, pathways from the lateral and medial divisions of the entorhinal cortex (LEC and MEC) to create memory representations for the content of an experience within its spatiotemporal context. Accumulated findings in our model and from other sources suggest that deficient processing in the LEC stream contributes disproportionately to the condition of age-related cognitive impairment. Across-project tests of this hypothesis will examine evidence at the level of neural encoding, connectional circuits, and cellular/synaptic function, with all investigations conducted in behaviorally-characterized subjects. Our studies will harness new technology for experiments in aging brains, including optogenetics and whole cell recording methods to study entorhinal input from LEC and MEC onto granule cells in the DG and a recently developed retrovirus/rabies virus tracing system to test a novel hypothesis regarding the integration of newly generated DG neurons as a basis for individual differences in aging with and without cognitive impairment. Finally, we will further study functional mechanisms that may uniquely distinguish successful aging from young adult brains, including recruitment of greater inhibitory control over the entorhinal/DG/CA3 network as an adaptive signature in aged rats with preserved cognitive abilities on a par with young.

This is an application for a Research Scientist Award (RSA) to support Dr. Michela Gallagher's research activities. Her research program is organized around two main lines of investigation. The first entails studies of neural systems involved in learning, an area of research that has been supported by NIMH since 1978. The research plan presented in this application builds on recent studies indicating a role for the amygdala in the regulation of attentional processes during associative learning. The second area focuses on the effects of aging on hippocampal/cortical systems, research presently supported by a National Institute on Aging program project grant. This research uses diverse methodologies (from behavioral analysis to molecular biological studies) in an examination of aging processes in the mammalian forebrain. The applicant's laboratory provides the Core Facilities for this multi- institutional effort. The studies in Dr. Gallagher's individual project within this program examines neurochemical systems in hippocampal pathways. Within the framework of her current activities, Dr. Gallagher has established a number of collaborations with other scientists. This network currently supports a strong interdisciplinary program of research drawing on advanced techniques in both neuroscience and the study of behavior. These collaborations also provide a favorable setting for extending the range of Dr. Gallagher's scientific training and expertise. Specific areas for future development in her work will include 1) the use of molecular neurobiological methods suitable for the study of neural systems (in situ hybridization methods) to complement other approaches already in place in the research program; 2) the use of computational modeling to examine the effects of aging on overall performance of neural systems, and 3) the extension of new models for amygdala function from rodents to the study of non-human primates. Collaborations are identified to support these objectives.

This multi-user biology equipment proposal requests funds to purchase a cryostat that will be used in a variety of research projects in the Psychology Department at University of North Carolina - Chapel Hill. The user group consists of four faculty with active research programs who are members of the Experimental and Biological Psychology Program (Gallagher, Lysle, Dykstra) and the Developmental Psychology Program (Gariepy). In addition, three of the users are members of the Neurobiology Curriculum faculty (Gallagher, Lysle, and Dykstra). The proposed cryostat will replace an American Optical cryostat purchased in 1984 at a cost of $5,016, which can no longer be serviced/maintained. The refrigeration unit of the existing cryostat contains CFCs that do not meet current standards. Parts for this machine also can no longer be replaced. The new equipment will provide facilities for the continued conduct of research projects for which the existing cryostat has been used. In addition, the new cryostat will have the precision needed for a number of projects for which the existing cryostat has been inadequate. For example, when uniform section thickness is crucial for quantitative work (e.g. using iodinated ligands) the investigators have had to arrange for time on a cryostat in the medical school. The purchase of a new cryostat with high precision for tissue sectioning will allow all research to be conducted within our multi-user facility. The proposed purchase is for a Leica 3000 cryostat with dual compressor and motorized handwheel ($28,625) and height adjustment module (additional $2,360). Thirty percent of the total cost will be provided from equipment funds in the Psychology Department (see attached letter in appendix from the Psychology Department Chair). As described in the detailed Description of Research, the applications for which a cryostat is needed range from standard histological methods to molecular neurobiological research. These latter inclu de studies using quantitative methods for in vitro autoradiography, mapping of labelled oligonucleotides administered in vivo and in situ hybridization histochemisty. In addition to serving the needs of the faculty within the user group, the equipment will also be extensively used in research training at undergraduate, graduate and postdoctoral levels.

The research in Project 2 addresses three of the Overall Program Objectives. As a component of Program Objective #1, behavioral studies will be conducted to assess the performance of aged rats on tests of attention, which are sensitive to immunotoxic lesions of cholinergic neurons in the basal forebrain in young rats. This behavioral characterization will provide a background for neurobiological studies in other projects (Projects 1, 5, and 6), and rats tested on these tasks will also be used under Aim #2 in this project to study the response of an immediate early gene to cholinergic activation. For this purpose in situ hybridization histochemistry (ISHH) for c-Fos mRNA will be used to map activation after a low dose of cholinergic agonist (pilocarpine) as a function of and behavioral impairment. This analysis will also address the 3rd Program Objective aimed at the study of signal transduction mechanisms. To achieve that program objective, we will in addition examine protein kinase C (Aim #1). We will assess mRNAs for several isoforms of PKC in hippocampus using ISHH. In a second series of studies, we will examine localization of PKC in cytosol and membrane fractions using Western blotting. These latter experiments will be conducted in two behavioral contexts: after a defined episode of spatial learning and following induction of behaviorally relevant plasticity in the hippocampal formation. The remaining experiments (in Aims 3 & 4) are designed to address specific hypotheses about the role of glucocorticoids in hippocampal aging (Program Objective #4). These studies will initially focus on adrenocorticoid receptor mRNA using solution hybridization assays to determine whether alterations in the aged hippocampus are related to behavioral impairment and to other associated alterations in hippocampal mRNAs, i.e. increased expression of mRNAs for glial fibrillary acidic protein (GFAP) and beta amyloid precursor protein (BAPP). In addition to characterizing the status of these mRNAs in intact young and aged rats, experiments will be conducted to determine whether glucocorticoid exposure plays a necessary and/or sufficient role in the emergence of mRNA signatures of hippocampal aging and hippocampal-depend behavioral impairment. Finally, experiments are designed to examine a possible basis for age-dependent differences in hippocampal glucocorticoid receptor (GR) function. Our studies will focus on AP-1 and its components Jun and Fos, which can determine whether genes regulated by GR are activated or repressed. We will examine the hypothesis that one or more Jun mRNAs are elevated compared to Fos mRNA in aged hippocampus, a condition that could lead to 'switching' GR function from repression to activation. We will then determine whether aging and/or cognitive impairment is associated with increased binding of Jun-related proteins (decreased Fos) to the GFAP-AP1 and/or proliferin composite element using gel shift assays.

The Core includes three components: 1) Administration; 2) Animal Resource; and 3) Data Management. The Administrative component maintains a network of communication among the individual projects and between the projects and Core activities. This includes providing material/animals from the Animal Resource to the component projects and transfer of results from project experiments to a centralized Data Management System. Administrative responsibilities also include organizing and implementing regular meetings. Of the entire Program Project, along with its scientific advisory panel. The Animal Resource is a pathogen-free vivarium of aged Long-Evans male rats located at UNC-CH. Behavioral characterization of all aged rats used for neurobiological studies in the component projects will be conducted. Substantial background research presented in the proposal serves as a basis for examining spatial learning as an assessment of cognitive function which predicts aging in hippocampal/cortical circuitry. The final component of the Core, Data Management, provides services to the Program in its data collection and analysis activities. This includes: 1) consultation with participants regarding study design, routine and non-routine analyses, and power calculations; 2) design and maintenance of centralized archives for data generated on the project, including inventory of the animal population, data coding and analytic file construction; and 3) development of linked databases to allow across- project analyses. The overall goal of Core activities is to maximize the benefit that can be gained by collaborative research in a program project configuration.

DESCRIPTION (Adapted from applicant's abstract): This is an application for a Research Scientist Award (RSA) to support Dr. Michela Gallagher's research activities. Her research program is organized around two main lines of investigation. The first entails studies of neural systems involved in learning, an area of research that has been supported by NIMH since 1978. The research plan presented in this application builds on recent studies indicating a role for the amygdala in the regulation of attentional processes during associative learning. The second area focuses on the effects of aging on hippocampal/cortical systems, research presently supported by a National Institute on Aging program project grant. This research uses diverse methodologies (from behavioral analysis to molecular biological studies) in an examination of aging processes in the mammalian forebrain. The applicant's laboratory provides the Core Facilities for this multi-institutional effort. The studies in Dr. Gallagher's individual project within this program examines neurochemical systems in hippocampal pathways. Within the framework of her current research activities, Dr. Gallagher has established a number of collaborations with other scientists. This network currently supports a strong interdisciplinary program of research drawing on advanced techniques in both neuroscience and the study of behavior. These collaborations also provide a favorable setting for extending the range of Dr. Gallagher's scientific training and expertise. Specific areas for future development in her work will include: 1) the use of molecular neurobiological methods suitable for the study of neural systems (in situ hybridization) to complement other approaches already in place in the research program; 2) the use of computational modeling to examine the effects of aging on overall performance of neural systems; and, 3) extension of new models for amygdala function from rodents to the study of non-human primates. Collaborations are identified to support these objectives. In addition to Dr. Gallagher's prior record of research, she has been active as an educator, training numerous pre- and postdoctoral students in both the Neurobiology Curriculum and the Psychology Department Program in Experimental and Biological Psychology. Her activities in professional societies and local community also show a commitment to science education, more broadly. The applicant plans to continue these activities at Johns Hopkins University to advance the training of future scientists for research careers in areas relevant to mental health.

DESCRIPTION (provided by applicant): Many clinical conditions are characterized by maladaptive behavioral control, such as eating disorders, addictions, obsessive-compulsive disorders, among others. Greater success in treating such conditions will come from a better understanding of the systems that provide control over motivationally based behavior. Our research supports a dual function model of the basolateral amygdala (BLA) in associative learning. Across a number of behavioral domains, BLA-dependent learning promotes action that is appropriate to the past experience of the organism, bringing species typical behavioral systems under strong motivational control by learned cues. Through associative learning such cues gain strength in the control of behavioral systems via outputs to hypothalamus and brainstem. At the same time, through its interconnections with cortical systems, BLA serves a second function in mapping predictive relationships between events, which are used in goal-directed behavior. That function of BLA makes a critical contribution to me top-down control of action, even in the face of strong response tendencies generated by lower-level learning. In our behavioral model for the first function of BLA, learning drives food consumption, such that conditioned cues, which signaled the availability of food when animals were hungry, augment food consumption in subsequent tests when satiation and replete energy stores. The proposed studies will define the contribution of components in this circuitry to acquisition, maintenance, and expression of conditioned potentiation of feeding. We will test the hypothesis that output to hypothalamus acts on the internal coding provided by satiety signals, and will examine the variable control of aversively conditioned cues on feeding, either suppressing or augmenting eating, as an output function of amygdala-hypothalamic circuits. To address the second BLA function, we will build on our finding that BLA integrity is essential for the development of cue-activated encoding of predicted outcomes in the orbitofrontal cortex (OFC) in an analysis of associatively activated flavor representations within a network of BLA-OFC-gustatory cortex (GC). The associative mapping of predictable events provides a template for flexible behavioral control, in which the value of a reinforcing event can be rapidly modified and continuously updated. We propose studies to determine the encoding properties of neurons in specific cortical regions and interactions among components of the network during learning and retrieval of associative information. We will further examine a basis for rapid top-down adjustments that occur in reinforcer devaluation paradigms. That work will examine specific neural coding in the cortical network that reflects changes in the value of predicted outcomes that can be used to control prepotent responses established by prior learning. A notable feature of the research on the neurobiology of these functions is the correspondence that exists in different species of laboratory animals (rodents and non-human primates) and the applicability of those findings to humans. As such, the work has important implications for clinical disorders of impulse and behavioral control.

The development of new technologies for manipulating brain function by gene targeting in mice has far outstripped the available behavioral methods for functional assessments. The current proposal will address three specific aims to develop additional behavioral models that are suitable for testing cognitive functions in genetically altered mice. Particular attention is given in the selection of these assessments to the need for time/cost efficient procedures that are, in addition, well grounded in both behavioral theory and studies of neural systems. One assessment of memory using retention for exposure to novel olfactory/gustatory information is intended to provide a highly efficient screen for medial temporal lobe function. The proposed studies include parametric examination of the properties of this model and test for its dependence on circuitry and neural mechanisms critical for other behavioral assessments that are less efficient to implement, such as models for spatial memory. In a second specific aim appetitive Pavlovian conditioning will be used to sequentially assess first-order conditioned responses, second order conditioning and the effects on behavior of devaluing the unconditioned stimulus. These tests provide analysis of motivational/incentive learning tied to specific neural systems. In the third specific aim we will develop a protocol for examining repeated acquisition of learning using new information in each test session. As a model, this olfactory guided learning task can be exploited to examine brain function concurrently with behavioral learning. Similar to the outline of studies for the first memory model, for each subsequent model proposed studies include parametric examination of the properties of the model and tests for its dependence on circuitry and neural mechanisms critical for the behavioral assessment. The models will be developed using F1 hybrids of C57B/6 129svImJ mice and comparisons with the inbred parent strains will also be made.

DESCRIPTION (Adapted from applicant's abstract): The long-term objective of this project is to evaluate the role of estrogen in modulating different types of memory and to understand the neural mechanisms underlying cognitive effects produced by estrogen as a function of aging. Ovarian steroids affect the brain throughout the life span and their effects are not limited to the areas primarily involved in reproduction, but also include the areas relevant to memory. Despite evidence that estrogen affects the brain, however, there have been no studies that directly test the effects of estrogen on memory as a function of aging. Our preliminary studies have indicated that ovariectomy (OVX) has a more rapid effect on cognition in older rats than in young. This has led to our main hypothesis that memory systems are more dependent on estrogens in aged rats. The main aims proposed in this application are to test the working hypothesis that with aging or long-term deficiency of estrogen, cognitive functions decline, and therefore, become more dependent on estrogens. Furthermore, it can be predicted that the types of memory that decline most with aging are most sensitive to estrogen. These studies will test these hypotheses in extended behavioral analyses that will produce detailed information on the interactions of aging and estrogen effects on cognition and the role of IGF-1 as a possible mediating mechanism for estrogen effects in the brain. The four specific aims that will be tested are whether 1) specific cognitive functions are more sensitive to estrogen, 2) with longer estrogen withdrawal cognition will decline more and effects of estrogen will depend upon the duration of the withdrawal, 3) estrogen effects differ as a function of aging, and 4) IGF-1 effects on NMDA receptors mediate the estrogen induced effects on cognition. The results of these studies will be the first to critically analyze the effects of estrogen on cognition as a function of aging, duration of estrogen deficiency and type of cognitive task and will also, test a potential neuroendocrine mechanism. Therefore, the data will be of importance in the understanding of age related changes in cognitive function and will have important clinical relevance.

This core is an essential component of the research program in its study of neurocognitive aging, providing an Animal Resource that serves each of the individual projects. A major objective of the overall research program is to elucidate the basis of neurocognitive aging in behaviorally characterized healthy aged rats. The overall research program further exploits the feature of individual differences in neurocognitive aging, a phenomenon that is well-documented in humans and captured in the animal model used in this research. The Animal Resource maintains a colony of pathogen-free male Long-Evans rats, which are additionally screened for disability and physiological impairment. All rats in the Animal Resource undergo assessment of cognitive function in a standardized protocol for "place" and "cue" learning in a water maze apparatus. The Animal resource provides analysis of these results to characterize presence/severity of impairment. Additional behavioral testing in this core will occur as specified for individual projects. Material from animals in the resource is then obtained for the projects, in a form appropriate to the methods used in the neurobiological studies (sacrifice/perfusion/dissection). In some instances live animals will be transferred ' from the Resource to projects for further in vivo analysis (i.e., electrophysiological recording) or to provide fresh tissue as needed for in vitro studies. In those cases Core B personnel work with the Administrative Core to obtain health certificates and prepare rats for shipping in an expedited manner. The Animal Resource Core compiles records on animal health, inventory, and analysis of the behavioral assessments, all in an archived form. In addition to providing rodent material for current projects, Core B also banks tissue specimens (dissected brain regions, peripheral organ tissues, blood samples) to be used at a later date by project investigators or outside scientists, This resource sharing activity is managed and coordinated by the Administrative Core (Core A). In an expanded set of objectives in the research program for the next funding cycle, Core B will also provide a resource of non-human primate tissue on young and aged monkeys that have been behaviorally characterized (behavioral studies conducted under the auspices of a separate funding mechanism [unreadable] RO1 AG10606 "Cognitive Function in the Aged Monkey). Thus, as promising results emerge for the rat model that has comprised the major focus of our efforts, we are uniquely positioned to test the generality of these findings in a well-characterized non-human primate model.

[unreadable] DESCRIPTION (provided by applicant): [unreadable] The Neurogenetics and Behavior Center, supported under this award, would establish a unique resource for NIH supported research programs using gene targeting technology to study basic functions of the brain and disorders relevant to psychiatric and neurological disease. The Center, through its Administrative, Animal Testing Facility, and Data Management functions will provide behavioral assessments in three broad functional domains: sensorimotor, affective processes, and cognition, the latter to include learning, memory, and attention. Phenotypic analysis in these domains will provide an immediate service to 33 investigators/research groups listed in the application, located in Maryland at JHU and the Kennedy Krieger Institute and at other sites (Massachusetts Institute of Technology, Brown University, and the Tennessee Mouse Genome Consortium, among others). In addition to providing a facility for standard behavioral testing and data analysis, investigators in the Center, who are internationally recognized behavioral neuroscientists, will work collaboratively to develop innovative assessments appropriate to the research goals of the users. These collaborations will not only enhance the quality of current investments in research programs funded by the NIH but will make a significant contribution to the field of neurogenetics through dissemination of the Center's activities. The Center will also provide a resource for training young scientists in the wide range of expertise needed to accomplish integrative research with animal models, bridging from genomic, molecular, and cellular levels of analysis to the study of behavioral systems and functional disorders. [unreadable] [unreadable]

neurogenetics; behavioral genetics; disease /disorder model; biomedical facility; animal colony; Rodentias; model design /development; behavioral /social science research tag;

The Administrative Core plays an integral role in the research program by coordinating activities and interactions between the Cores and individual projects. The roles of the Administrative Core in 1) animal/tissue assignment to the Projects from Core B, and 2) data transfer from the Projects to Core C, achieves an organizational structure whereby all records of planned research, active experiments, and completed research, including publications, are coordinated and maintained with a central point of contact. The Administrative Core, additionally, organizes program events and meetings, including our external scientific advisors. The participation of a scientific advisory group in our planning/review process provides valuable oversight and consultation. In addition to such meetings, all investigators, including Core and Project Leaders are updated on the work in the research program through Core A's data sharing function. Together, these activities are integral to guiding the research program through each annual cycle of planning, discovery, and evaluation of research findings/productivity. In these functions, the Administrative Core contributes significantly to the integration of work in the research program. The Administrative Core has well-established procedures for all of its functions. With respect to the assignment of resources for experiments (animals and tissue), the program has extensive experience in handling/shipping of materials and animals to the participating projects. Under our long-established system, unique identifiers for each subject/sample then ensure that studies in the projects are conducted blind with respect to cognitive status. Data transfer through the Administrative Core to Data Management (Core C) provides a clear point of contact to ensure complete archiving (data obtained/transferred for all assigned animal resources) and for tracking progress on research in the projects. The meetings of the entire program project, along with updates managed by the Administrative Core, are integral to the review of our progress, plans for the future, and integration of the program. The Administrative Core also provides routine support for the overall program project (oversight of finances, progress reports and continuation applications). Finally, in addition to its functions in resource sharing (animals/tissue, data) within the research program, the Administrative Core also oversees, manages, and coordinates resource sharing with outside investigators.

This Project will continue its focus on signaling and plasticity as a basis for individual differences in aging outcomes. Against a background of largely preserved structural integrity, alterations in the function of neurons in the medial temporal lobe provide the most reliable indicators of cognitive abilities that depend on this circuitry. The background and preliminary data for this research plan indicate a basis for distinguishing two subpopulations of aged rats that each differ from young. Consistent with recent findings in other components of the overall research program, the CAS region of the hippocampus is particularly noteworthy as an area that undergoes pronounced alterations associated with cognitive impairment. A distinctive profile is also found in this region in aged animals with preserved cognitive function. The Specific Aims of this project will 1) extend the regional analysis of broad molecular profiling in behaviorally characterized aged rats to a paradigm for measuring learning-activated transcription (Aim 2), and 2) assess the efficacy of interventions to gain control over the dysregulaton of cellular function in impaired aged rats and determine whether the such treatments normalize indicators in the molecular profile in both basal and learningactivated conditions along with improved behavioral outcomes (Aim 3). The purpose of studies using interventions based on data in the model is twofold, 1) to allow the test of specific scientific hypotheses, and 2) to examine new avenues into translation approaches for therapy. Test agents under study in the proposed work include 1) antiepileptics (valproate and ABT 769), 2) HDAC inhibitors (sodium butyrate and MS 275), and 3) agonists selective for GABA-A a5 receptors. In Specific Aim 4 we will examine the basis for differential adaptive aging in rats that perform on a par with young adults. That work will explore a new hypothesis concerning alterations in middle-age that may serve an adaptive function in aging outcomes, both neuroprotective and behavioral. Such adaptations would be consistent with a switch in plasticity mechanisms observed in aged unimpaired rats. Finally, research under this project will examine whether signatures of neurocognitive aging in subregions of the hippocampal system in rats have a counterpart in aged monkey brains. Importantly those studies, similar to our research with aged rodents, will use brain tissue obtained from behaviorally characterized young and aged rhesus monkeys. We will ask questions that are based on the conditions of different aging outcomes in the rodent, including 1) overall profiles that relate to cognitive status in the aging primate (e.g. impaired and adaptive), 2) the status of specific genes that are markers of neurocognitive aging in the rodent (CAS and CA1 regions), and 3) pre- and post-synaptic gene expression patterns in arrays of dentate gyrus and entorhinal cortex that may serve as a basis for synaptic failure in the connections formed by the perforant path.

DESCRIPTION (provided by applicant): This project will seize on new evidence that excess activity in the CA3 region of the hippocampus occurs both in aged animals with memory impairment and in patients with amnestic Mild Cognitive Impairment (aMCI), a condition that commonly precedes the development of AD. Treatments that target this excess activity in the preclinical animal model are effective in improving memory performance and in rescuing the ability of the targeted neurons to encode new information in memory. Because the CA3 dysfunction studied in animals can now be observed in high resolution functional neuroimaging (fMRI) in patients with aMCI and effective treatments in the preclinical setting have included compounds approved for use in man, here we will test whether a therapeutic intervention based on the animal model can lower excess activation in the CA3 and improve memory in aMCI. High-resolution fMRI will be conducted during a task that places demands on pattern separation, a memory function that specifically depends on the CA3 region. Recent work showed that aMCI patients have impaired memory on the pattern separation task and hyperactive BOLD signals in the CA3/DG during the conditions that tax pattern separation compared to age-matched controls. Significant negative correlations between performance on the target test items and hyperactivity during both encoding and retrieval suggest that excess CA3/DG activation is dysfunctional. The proposed study will experimentally test that hypothesis. The design will determine a treatment regimen that lowers hippocampal hyperactivity in aMCI and assess whether corresponding gains occur in memory performance in the pattern separation task, as predicted by research in the animal model. Participants on placebo and drug, counterbalanced within-subject, will also be tested outside the scanner with other assessments widely used to evaluate memory function. We have assembled an expert team of investigators and an external advisory group to guide this effort in an adaptive design with an exploratory phase (Year 1) and a confirmatory phase (Year 2). Findings from this project would have high impact as an experimental test of whether excess activity serves a compensatory function, as originally suggested in reports of increased hippocampal activation in MCI fMRI, or is in fact a dysfunctional condition, as demonstrated in the animal data. Because increased hippocampal activation in MCI also predicts further decline and progression to AD, the proposed research could be a first step in developing interventions that not only improve cognition in aMCI but also modify progression to AD. That approach is further encouraged by new data on excess neuronal activity in several mouse models of AD and prior research on the production of A beta driven by neural activity, observations that extend a role for excess activity in neurocognitive aging to a possible basis for aging as a primary risk factor for AD. In light of forecasts for a staggering burden of AD in the decades ahead if effective therapies are not found soon, this novel entry point for therapy at an early stage of cognitive impairment has great potential in a critical area of unmet medical need. PUBLIC HEALTH RELEVANCE: Aging is often associated with cognitive deficits, especially decline in memory functions. Aging is also the major risk factor for Alzheimer's Disease (AD), the most common form of dementia. This project will test a new modality of therapy directed at memory impairment in the elderly, which may also have potential to modify a transition from mild cognitive impairment to Alzheimer's disease. It will use tests of memory together with brain imaging to determine the effects of therapy in persons over the age of 55 who meet diagnostic criterion for amnestic mild cognitive impairment. )

The animal behavioral core will support activities across the research program by conducting assessments in mouse genetic models of the 'DISC1 interactome' that will be informative about brain circuitry and psychological processes implicated in schizophrenia. The primary behavioral battery, in line with the neurodevelopmental perspective of the research program, is focused on component functions of prefrontal cortex. Paradigms developed for this purpose have revealed behavioral phenotypes clearly indicative of frontal cortical dysfunction in DISC1 transgenic mice. The use of a common behavioral platform across projects with different genetic models will provide data relevant to mechanistic hypotheses, complementing the experimental approaches used by individual investigators. The functional assessments will address behavioral flexibility, goal-directed action and the interface of action/effort with attributes of reward experience and incentive learning. Specifically, the activities of the core will 1) plan, design, and implement behavioral experiments with a focus on analytically powerful protocols targeting the prefrontal and associated forebrain systems; 2) provide data analysis and interpretation of findings in support of the projects, including preparation of publications; and 3) database development for all data in the platform of behavioral assessments to allow across-project analyses and data-sharing beyond the research program.

The Animal Resource Core (Core B) is an essential component of the research program in its study of neurocognitive aging to provide young and aged rats to each of the Projects. A major objective of the overall research program is to elucidate the basis of neurocognitive aging in behaviorally characterized healthy aged rats. The overall research program further exploits the feature of individual differences in neurocognitive aging, a phenomenon that is well-documented in humans and captured in the animal model used in this research. The many years of work with this outbred model of male Long Evans have established that a subpopulation at older ages exhibit impaired performance while other rats in the aged cohort maintain preserved performance on a par with young adults. These well-characterized individual differences have been used successfully to examine neurobiological variations in the medial temporal lobe that are closely coupled to cognitive outcomes. The Animal Resource (Core B) maintains a colony of pathogen-free male Long-Evans rats, which are additionally screened for disability and physiological impairment. All rats in the Animal Resource undergo assessment of cognitive function in a standardized protocol for ?place? and ?cue? learning in a water maze apparatus. The Animal Resource together with the Data Management (Core C) provides routine analysis of these results to characterize presence/severity of impairment. Additional behavioral assessments (e.g. object recognition) are provided for specific project experiments. The Animal Resource compiles records on animal health, inventory, and analysis of the behavioral assessments, all in an archived form maintained by Core C (Data Management and Statistics). Animals from the resource are then made available to the Projects for further studies, with assignments under the supervision of the Administrative Core (Core A). In many instances live animals are transferred from the Resource to projects for further in vivo analysis (i.e., electrophysiological recording, additional behavioral assessment) or to provide fresh tissue as needed for in vitro studies. In addition to providing rodent material for current projects, Core B also banks tissue specimens (dissected brain regions, peripheral organ tissues, blood samples) to be used at a later date by project investigators or outside scientists, This resource sharing activity is managed and coordinated by the Administrative Core (Core A).

The Administrative Core (Core A) is led by Dr. Michela Gallagher, who serves as the P.I. of this Program Project grant. The Administrative Core plays an integral role in the research program by coordinating activities and interactions between the Cores and individual projects. The roles of the Administrative Core include 1) animal/tissue assignment to the Projects from Core B, 2) oversight of data transfer from the Projects to Core C, and 3) transfer of Core B data for routine analysis and archiving by Core C, achieving an organizational structure whereby all records of planned research, active experiments, and completed research, including publications, are coordinated and maintained with a central point of contact. The Administrative Core organizes program events and meetings, including meetings with our external scientific advisory board. The participation of a scientific advisory group in our planning/review process provides valuable oversight and consultation. In addition to such meetings, all investigators, including Core and Project Leaders are updated on the work in the research program through regular group meetings and Core A's data sharing function. Together, these activities are integral to guiding the research program through each annual cycle of planning, discovery, and evaluation of research findings/productivity. In these functions, the Administrative Core contributes significantly to the integration of work in the research program with transparency and building consensus on decisions. The Administrative Core has well-established procedures for all of its functions. With respect to the assignment of resources for experiments (animals and tissue), under our long-established system, unique identifiers for each subject/sample ensure that studies in the Projects are conducted blind with respect to cognitive status. Data transfer through the Administrative Core to Data Management (Core C) provides a clear point of contact to ensure complete archiving (data obtained/transferred for all assigned animal resources) and for tracking progress on research in the Projects. The meetings of the entire program project, along with updates managed by the Administrative Core, are integral to the review of our progress, plans for the future, and integration of the program. The Administrative Core also provides routine support for the overall Program Project (oversight of finances, compliance with all NIH guidelines, progress reports and continuation applications). Finally, in addition to its functions in resource sharing (animals/tissue, data) within the research program, the Administrative Core also oversees, manages, and coordinates resource sharing with outside investigators.

? DESCRIPTION: No therapy has FDA approval for amnestic MCI, a symptomatic stage of Alzheimer's disease when patients are at increased risk for progression to dementia. Using an agent with proven safety/tolerability, we propose a novel approach for slowing progression in MCI due to AD. The use of the atypical antiepileptic levetiracetam (LEV) is indicated by evidence that hippocampal hyperactivity is characteristic of this stage of disease, predicts subsequent longitudinal cognitive decline/conversion to a dementia diagnosis, and is correlated with the extent of neuronal injury as measured in structural MRI. Supporting the proposed therapy, low dose treatment with LEV reduces hippocampal hyperactivity in both animal models and aMCI subjects, concurrently improving cognitive function. In the longer-term, treatment with LEV is expected to reduce degenerative processes driven by failure to control excess neural activity in the vulnerable entorhinal/hippocampal network. The proposed randomized, placebo-controlled 24 month trial will test the efficacy of LEV therapy on a sole primary outcome, the CDR sum of boxes, and a key secondary measure of entorhinal cortex thinning to assess neuronal injury. The trial will also acquire a rich database, e.g. genetic/DNA, additional imaging modalities (resting state fMRI, and diffusion tensor imaging scans), along with both standardized neuropsychological testing and novel cognitive assessments as secondary measures. Funding under this application would provide partial support (approximately 15% of total trial cost) in a public/private partnership for this Phase II/III trial, which would be the first to target hippocamal hyperactivity and will be registered with the FDA. A pre-IND meeting with the FDA (March 2014) on the proposed protocol provided supportive background on all aspects of the trial plan including appropriate enrollment criteria, adequacy of outcome measures, drug safety, and CMC formulation of an extended release medication. Importantly, the FDA confirmed that no further preclinical or clinical data are required to proceed with the trial. The Hopkins investigators under this award, who have exceptional expertise in biostatistics, imaging, clinical trial design, and data analysis have worked together with the Sponsor (AgeneBio, Inc) and its CRO to develop the protocol and plans to implement it. NIH support would not only contribute to the main purpose of the trial, but also ensure an open resource for data sharing to advance clinical trial design in AD prevention, including biomarker development.

Studies in outbred Long Evans rats have contributed to the identification of a neurobiological basis for cognitive impairment in the aged brain of otherwise healthy laboratory animals. Within the medial temporal lobe memory system the selective loss of perforant path connections and an altered condition of the network it innervates in the dentate gyrus (DG) and CA3 region are hallmarks of rats that age with memory impairment. In contrast, that network is relatively maintained in aged rats with preserved cognitive function, including anatomical integrity of the perforant path and a balance of computational properties for pattern separation and pattern completion in DG/CA3 that resembles young adults. A unique feature of this network is the integration of new DG neurons in the adult brain. No studies have yet examined that integration in the context of brain aging. The proposed research in Project 2 will complement studies in the other projects by examining whether the integration of newly DG generated neurons aligns with individual differences in cognitive outcomes. Unimpaired aged rats, consistent with young adults may show a predominant role for the lateral entorhinal cortex (LEC) in the integrating network. Because the circuit integration of new DG neurons involves other elements that strongly differentiate cognitive outcomes, such as hilar interneurons, CA3 neurons, and basal forebrain cholinergic projections, we will determine whether a broad difference in the circuit integration of new DG neurons occurs in impaired and unimpaired aged rats. In addition to a better understanding of the basis for age-related impairment, the findings will be informative about the condition of the aged brain that maintains a high-level of cognitive capacity, e.g. testing the hypothesis that such animals (but not impaired aged cohorts) integrate a complement of new DG neurons in a manner similar to young. Additional studies in this project will further test whether an impoverished integration in impaired aged rats can be improved by a therapeutic treatment that has been shown to boost molecular markers in key monosynaptic afferents in the entorhinal cortex and DG/hilus. Those findings, together with studies in Project 1 and 3, will address an emerging hypothesis in this research program that a failure through the LEC steam of information processing disproportionately contributes to memory impairment in the aged brain. Alongside better maintenance of those properties in aged unimpaired rats, research in this model suggests that adjustments in the aging brain, which are distinct from young adults, contribute to preserving cognitive function. Project 2 will further examine whether unimpaired aged rats engage greater inhibitory control over the entorhinal/DG/CA3 network as suggested by our findings. Neural overactivity in the brains of impaired aged rats, and a parallel condition detected by functional imaging in studies of human aging/MCI suggest that recruitment of inhibitory control in unimpaired aged rats could play an adaptive beneficial role in neurocognitive aging.  

Research under the current proposal is designed to determine behavioral alterations relevant to schizophrenia (SZ), which is elicited by activation of stress-associated cascades and the E-I imbalance in the prefrontal cortex in mouse models that carry microtubule-associated genetic variants. We will also study how adolescent social isolation exacerbates these changes at the molecular, circuitry, and behavioral levels in collaboration with three Projects. In addition to performing basic behavioral characterization of the mouse models, this Core will conduct behavioral assessments for neurocognitive domains that are mediated by medial prefrontal cortex and orbitofrontal cortex, such as behavioral flexibility, including outcome expectancy in goal directed behavior, and working memory. Our rationale for use of specific behavioral assessments aimed at prefrontal systems is grounded in research that 1) documents the critical role of prefrontal cortex (PFC) circuitry in the information encoding mechanisms required to support behavioral performance in these paradigms across rodent and primate species, 2) implicates PFC systems supporting these functions in SZ by anatomical and physiological/neuroimaging evidence from patients, 3) demonstrates a vulnerability of such PFC-mediated behaviors/networks to stress exposure, including underlying mechanisms in PFC. Importantly, the assessments hold potential for the study of species-conserved cognitive mechanisms in the human brain to provide translational opportunities based on this preclinical research program. As such, the work in Core C is consistent with the Research Domain Criteria (RDoC) approach for advancing a biological understanding of the pathophysiology of major psychiatric illness and creating a platform for discovery of new therapeutics. Core C will consult with the investigators of the Projects both for conducting basic behavioral assays, for implementing behavioral experiments with a focus on analytically powerful protocols targeting PFC-mediated behaviors, and will lead data analysis and interpretation of findings in behavioral studies under the research program. In addition to its scientific value to the immediate objectives of the research program, the work of this Core may have broader translational significance in the neuropsychiatric field. As the molecular pathways under investigation are better understood in the context of behavioral profiling, the work of the core could identify assessments that are best suited to target dysfunctional mechanisms in animal models of SZ. In this way the proposed behavioral research may yield innovative findings of more general preclinical importance.

This research program represents a multidisciplinary, integrated approach to understanding the effects of normal aging on a critical brain system that supports cognitive functions affected in humans as they age. We focus on brain aging in hippocampal/cortical circuits using Long Evans rats, an outbred strain that exhibits individual differences in aging outcomes in well-characterized cognitive assessments. At older ages (24-26 month) cognitive impairment affects 50-60% of healthy male rats in this population, while the remaining aged cohorts fall within the range of young adults (4-6 months). Research under this mechanism of support has identified alterations in the brain that are tightly coupled to these cognitive outcomes, including the deleterious effects of heightened neural activity in specific hippocampal circuits on memory function in aging. The current proposal will include a direct comparison of individual differnces in neurocognitive aging in both male and female outbred Long Evans rats (Core B). Our proposed plans will build on our achievements to leverage new findings that will advance understanding of episodic memory in basic research with application to clinical problems in aging. Our research program to date has translated successfully in studies of human aging. Now in reverse-translation we will examine the homeostatic control of network/circuit function by a mechanism that clinical studies have implicated in late-life cognitive outcomes as well as in risk and resilience for late-onset AD; Its failure across the spectrum of aging/AD in the human brain is closely tied to cognitive impairment. Our studies on homeostasis regulated by NPTX2/GluA4 will provide the first systematic basic research in aging focused on hippocampal circuitry where loss of inhibitory control has been identified in the condition of impairment in the Long Evans model. Further studies, including those on NPTX2/PV-interneurons will focus on evidence for an augmentation of inhibition in aged rats with preserved cognitive function, relative to young adults. We are testing the functional significance of that condition as serving a potential role in adaptive aging to maintain excitatory/inhibitory balance and cognitive performance. New tools and methods for the study of brain aging will advance the overall research program together with direct comparisons for individual differences in aged female and male rats. To that end, three Cores (Administrative, Animal Resource, and Bioinformatics/Data Management) will serve all of the participating investigators conducting research in the four proposed projects.