Kay M. Tye, Ph.D. - US grants

Obesity and Type 2 diabetes have skyrocketed to epidemic proportions in American children and adults. To prevent the onset, initiate the reversal, and avoid the relapse of obesity, we must first identify the neural underpinnings of unhealthy eating choices and habits. The immediate goals of this innovative proposal are to decipher the neural code predicting compulsive overconsumption of sugar and to develop new approaches, algorithms, and technologies to detect neural signals of craving in real-time to avert maladaptive behaviors with unprecedented precision. Specifically, the project outline will begin by identifying neural circuits mediating compulsive sucrose seeking. Next, we will record neural activity using in vivo electrophysiology and fluorescence microendoscopy of GCaMP5-expressing cells to collect precise, first-order, raw features with high signal-to-noise ratio during cue-induced reinstatement and compulsion behavioral assays with their time-locked neural correlates allows for the identification of craving states. Then, we will use machine learning algorithms such as support vector machine classification of neural activity allows for a Bayesian hidden Markov model for a transition diagram between states in craving-compulsion-consumption behavioral chains. Following identification of neural activity signaling ?craving? states (operationally defined as the behavioral state immediately preceding compulsive reward-seeking), real-time state detection will be used to trigger precise optogenetic inhibition of compulsive sucrose-seeking. A successful outcome of this research would establish a new paradigm for the treatment for obesity, focusing on reprogramming the neural circuit perturbations that cause obesity, as opposed to treating the physical consequences of a neural circuit imbalance ? an approach that could also be applied to other neuropsychiatric disorders including addiction, anxiety, depression, bipolar disorder and obsessive compulsive disorder (OCD). This proposal is ideally suited for the New Innovator Award for the following reasons: First, the ultimate goal of this research is to lay the foundation for translating Neural Circuit Reprogramming to human patients. Second, the proposal is focused on technology development, delivering new technologies that will enable not state-identification and dynamic triggering used for Neural Circuit Reprogramming, and serve as springboards for other fields. Third, this proposal heavily leverages my unique background in sucrose-self administration, relapse, optogenetics, electrophysiology and imaging, but is technically and conceptually distinct from my lab?s other studies on acute perturbations that affect anxiety, depression and addiction. As a new faculty member at MIT, I am poised at the nexus of science, engineering, computation and technology and am equipped with the precise skill set and expertise to execute this high-risk, yet potentially revolutionary project.

This project consists of engineering a system for producing selective expression of light-inducible molecules in targeted neuron population in non-genetically modified animals of any species. The result will be a set of reagents that will be made freely available to the scientific community through nonprofit repositories and service centers. This new set of tools will enable the study of neural circuitry with greater resolution, power, and throughput than is currently possible, allowing major advances to be made in understanding the organization of the complex neural systems underlying perception, cognition, and behavior. This increased understanding could also result in improved artificial intelligence and machine learning. Finally, the future direct application of the technology in human patients holds promise for potentially treating conditions such as Parkinson's disease and epilepsy, by allowing the selective activation or inactivation of distinct components of the compromised neural circuitry that is associated with these disorders.

Over the last decade, sophisticated genetic tools have been developed that allow control and monitoring of neuron electrical activity using light alone. "Optogenetics", as this area of technology has become known, is only useful if optogenetic molecules can be specifically expressed in functionally meaningful groups of neurons instead of broadly in all the diverse neuron types that are present in any brain region. This requirement has confined their use almost entirely to genetically modified (transgenic) mice and rats. The approach of using transgenic animals has three major disadvantages. First, the production and maintenance of transgenic rodents is very expensive. Second, even within transgenic rodents, it allows the optogenetic study and manipulation of only one or two cell types at a time, preventing powerful combinatorial experiments in which different neuron types are independently controlled within the same tissue. These combinatorial experiments will be critical for deciphering the complex interactions between cell types. Third, it restricts the experiments to rodents, preventing studies in other important taxa including primates, in which optogenetic experimentation during complex cognitive tasks would almost certainly provide major insights into the neural circuitry underlying cognition. This project aims to create engineered binding proteins that recognize selected endogenous proteins that will then act as scaffolds for assembly of transcription factors that will activate gene expression in specific neurons.

DESCRIPTION (provided by applicant): The two primary classes of emotional or motivational valence are seeking pleasure and avoiding pain. The ability to distinguish good and bad environmental cues is critical for survival, and perturbations in this ability can result in aberrat behaviors relevant to psychiatric disease. While the amygdala is known to be a region critical for processing motivational valence, a fundamental question in neuroscience is: How can opposing behavioral outputs be mediated by a similar neural mechanism? One likely possibility is that the processing of positive or negative motivation valence occurs with divergence into largely distinct circuits. Electrophysiological recording studies from the last decade provide compelling evidence that the amygdala could act as this initial divergence point. However, this hypothesis has not been directly tested. Here, we propose to directly test the hypothesis that positive and negative valence processing diverges at the basolateral amygdala, which projects to both the fear and reward circuits. We will test whether downstream projection targets define these different populations in both innate and learned associations, explore whether neural activity and synaptic plasticity are occurring preferentially in projection-defined neural populations, and identify novel targets in the fear and reward circuits. Our compelling preliminary data sets demonstrate the feasibility of applying multiple cutting-edge techniques to testing the specific hypotheses regarding causal relationships between specific neural projections and behavior, characterizing the cellular and synaptic mechanisms, and expanding our current knowledge of motivational circuitry. Specifically, this investigator has extensive expertise in projection-speciic optogenetic manipulations, electrophysiology, immunohistochemistry and pharmacological manipulations to study the neural basis of motivated behaviors. A successful outcome of the proposed research will establish a major conceptual advance in understanding the neural basis of positive and negative valence.

DESCRIPTION (provided by applicant): Recent research suggests that the presence of neuropsychiatric symptoms is a risk factor for progression from mild cognitive impairment (MCI) to Alzheimer's disease (AD), and an individual's susceptibility to distress significantly increases their risk of AD. These findings imply that poor resilience to behavioral stress is not simply a characteristic of dementia, but may reflect mechanisms involved in disease etiology. The increased activation of stress-related brain circuits, such as that between the basolateral amygdala (BLA) and the hippocampus, may underlie aspects of hippocampus pathology and exacerbate memory impairment in AD. However, the mechanistic link between behavioral stress, amygdala output, and hippocampal dysfunction in the normal and diseased brain remains unclear. Our preliminary results utilize optogenetic and pharmacogenetic techniques to show that activation of specific BLA afferents to the hippocampus mimics the effects of behavioral stress upon both cellular pathology and cognitive function. Importantly, silencing these pathways prevents cognitive impairment following repeated behavioral stress. Moreover, chronic inactivation of this circuit appears to ameliorate AD-like phenotypes in a mouse model of familial AD. Therefore, the BLA- hippocampus circuit, so heavily implicated in the impact of stress upon hippocampal function, should be closely evaluated, in a manner only achievable via the use of cell- and circuit-specific optogenetic techniques, for its contribution to cognitive dysfunction and cellular pathology in AD. Our preliminary data also show that the BLA- hippocampal stress circuit is not comprised of a solitary pathway, but that the ventral and dorsal components of this circuit may play differential roles in the modulation of anxiety and the impact of behavioral stress upon cognitive function. This application will test the hypothesis that the activation of BLA input pathways to the HPC as a result of behavioral stress leads to the exacerbation of AD pathology, and will determine the relative contribution of the ventral and dorsal components of this pathway. These studies will examine how the targeted silencing of specific brain circuits can slow disease progress and ameliorate cognitive impairment, and may provide rationale for the application of deep brain stimulation techniques in the treatment of AD.

Intricate social hierarchies that go through both dynamic and stable phases exist in species ranging from humans to mice to insects and have been richly described in psychology and ecology, but virtually nothing is known about the neural circuit mechanisms that govern the remarkable coordination of large groups of animals. Systems neuroscience has exploded with a number of novel technologies, yet the culture of this field has been largely reductionist ? focusing on animals living in isolation or with a single-digit number of cage mates performing highly-controlled tasks. Although there is abundant ongoing research in the domain of social reward (motivation to engage in social behavior for hedonic value that social interaction provides), there is no ongoing research (to my knowledge) examining the neural representation of a negative valence need state (a loneliness-like state), the social homeostatic set-point, or how this is related to social rank. Indeed, this unexplored face of social behavior may have greater relevance to mental health and the burden on society. This proposal is completely different from any previous work done by myself or any investigator because we will do the following: 1) present a model for social homeostasis where social rank dictates the set-point for quality/quantity of social contact; 2) bridge behavioral ecology and systems neuroscience by using complex, naturalistic vivariums of large groups of mice in combination with nascent neural recording technology and expertise across a wide range of functional circuit dissection techniques; 3) simultaneously record across many brains using wireless recording devices to determine how composite dominance hierarchy is represented and determine whether meta-brain patterns for group social homeostasis (in both stable and dynamic phases) exist and observe how they change during dominance hierarchical reorganizations; and 4) identify site(s) and circuit(s) that represent social rank by applying machine learning approaches to decode ensembles that accurately predict the animal?s social rank, and use this information to move towards a mathematical model for social homeostasis on a supraorganismal group level.

Project Summary Optogenetic approaches, which include the activation, inhibition and modulation of specific circuit components using light-sensitive genetically-encodable proteins, have greatly advanced our ability to study how the brain gives rise to behavior. The ability to manipulate and observe the activity of specific cell-types with millisecond precision has completely revolutionized the field of neuroscience and launched us into an era of studying neural circuits, including those deep within the brain such as the basal ganglia or limbic circuits. Indeed some of the most impactful studies in a number of fields have been made possible with optogenetics, including breakthroughs made in understanding sleep processes, emotional valence processing, memory formation, habit formation, reward seeking and compulsive drug-taking behaviors. The 2018 ?Optogenetic approaches to understanding neural circuits and behavior? which will be held July 15 ? 20, 2018 at the Sunday River Resort, Newry, ME will be second meeting ? following up on a very successful inaugural meeting. The development of this meeting has been hotly anticipated as similar one-time meetings have been wildly successful in terms of the participants, the lively discussion, and the impact on future work. Now, we have turned to the Gordon Research Conference (GRC) format to establish a meeting that will occur with regularity (biennially) and will feature the most exciting unpublished findings from internationally renowned basic and clinical researchers. The long-term goals of this meeting are to bring all fields of neural circuit investigation up to the same high standard and to advance our understanding of neural circuits in the context of disease-relevant behaviors. By understanding the neural circuit mechanisms of various disease states, we will have a much stronger foundation from which we can launch new biomarkers for individualized medicine and to develop circuit- informed therapies that will be more specific with fewer undesirable side-effects.

Humans possess a fundamental need for social contact, which is essential for survival and mental well- being. Therefore, situations of social isolation, exclusion, or disconnection are highly aversive, and can lead to negative feelings of loneliness. However, we have a poor understanding of the brain circuitry which underlies this emotional state, and how this generates a need to seek social contact. Additionally, in many neuropsychiatric disorders, including depression, anxiety, and autism spectrum disorders social withdrawal and impaired social interaction are defining features. As a first step, we must uncover the neural mechanisms which underlie our inherent drive to seek and engage in social contact, in order to understand how these might go awry in mood disorders. We have recently gathered exciting preliminary data implicating an understudied population of dopamine (DA) neurons in the dorsal raphe nucleus (DRN) in representing the subjective experience of social isolation. We find that these neurons are sensitive to acute periods of social isolation, and manipulations of their activity in vivo can induce or suppress a ?loneliness-like? state, in a manner predicted by social rank. We hypothesize that the DRN DA neurons mediate a ?loneliness-like? state, and provide the motivational drive to re-establish social contact. With this research proposal, we therefore seek to explore and unravel this largely uncharted territory within the dopaminergic circuit and explore its functional importance for social contact. To achieve this, we will first identify the input-output architecture of this type of neurons. This will generate a neuroanatomical roadmap and the foundation for detailed circuit- and projection-specific analyses. Furthermore, we will test which input and output regions are involved in conveying essential information about the social environment. For this we will examine the naturally-occurring activity within the DRN dopamine neurons, and establish how manipulating their activity affects social behavior. This will provide insight into how the neural dynamics of this population differ in grouped and socially-isolated animals. We will additionally explore the DRN DA system in relation to the establishment and maintenance of social hierarchy. These experiments will unravel the relationship between DRN DA function and social rank, and further our understanding of the neural mechanisms which contribute to individual differences in social behavior. Importantly, we will work with Ian Wickersham and Liqun Luo to be at the forefront of viral vector approaches needed to successfully execute this proposal. Given my lab?s track record, the unique preliminary data set generated by my team, the questions identified and the necessary steps already taken, we are particularly well-suited to execute this study, and are thrilled to drive the field of social neuroscience forward.

Project Summary The Salk Institute for Biological Studies is an independent, non-profit research institute in La Jolla, CA that focuses on fundamental basic science research. Shared resources and cores provide critical support for this research. Eleven technology cores serve the Institute, including the Waitt Advanced Biophotonics Core Facility, which is solely dedicated to technologies relating to multiscale light and electron microscopy imaging and analysis. This Core has a significant dependency on confocal microscopy. Confocal microscopy is a powerful research technology that is heavily utilized by NIMH-supported Salk scientists. In recent years, usage of core confocal microscope systems has increased significantly, and the ability to accommodate all requests has been possible only by operating all three existing confocal microscopes at near maximum capacity. However, the Zeiss 710 is over a decade old. This instrument has limited technical capabilities, decreasing reliability, and is near the end of its practical lifetime. The purpose of this grant application is to address a pressing and unmet need for a replacement instrument, by the acquisition of an Olympus FV3000RS TruSpectral Hybrid scanning confocal microscopy system. This new instrument would replace the aging Zeiss 710, which will be placed on the resale market, donated to a non-profit organization, or recycled. The FV300RS is a best-in-class instrument, ideally suited to the demanding imaging needs of Salk NIMH- supported researchers and others. It offers a vast improvement in imaging technology that meets the more advanced needs of the field. The system as configured has 7 excitation laser lines and unique holographic spectral separation technology that offers real-time 16-channel spectral separation with 2 nm resolution and very high light transmission. This improves signal to noise and offers true spectral un-mixing for challenging multispectral imaging needs. In addition, it has bi-modal scanning capabilities, allowing either super resolution precision laser scanning or very fast resonant laser scanning. It has 4 high sensitivity GaAsP photomultiplier detectors and is equipped with the new Olympus X-line objectives that offer unparalleled chromatic correction and image flatness without sacrificing high numerical aperture or large fields of view. For challenging 3D multispectral imaging of large tissue volumes that are needed for whole brain connectome and cell identity studies, this system has been configured with Olympus?s unique silicon immersion 40X objective. This is specifically designed for whole brain cleared tissue imaging. As configured, the FV3000RS TruSpectral Hybrid scanning confocal microscopy system offers flexible macro-to-micro scale, rapid and super-resolution multidimensional imaging of fixed and live samples and provides a complete imaging solution for the demanding needs of current and future neuroscience research. With the experience and expertise provided by the Waitt Advanced Biophotonics Core facility, this new instrument will be immediately put to a high level of use to facilitate scientific discovery.

PROJECT SUMMARY The ability to discriminate between what is ?good? and ?bad? is termed valence processing, and pathological perturbations in valence processing can explain mental health disorders ranging from anxiety and depression to compulsivity and bipolar disorder. The key to developing more effective treatments for mental health disorders with fewer side-effects will be in the synaptic, cellular, and circuit mechanisms. This proposal not only lays out a very specific research plan to probe the functional role of a neuropeptide, neurotensin (NT), but it also lays out a comprehensive, systematic approach to investigating neuromodulatory systems. The general approach includes: 1) Identify a circuit that plays a causal and critical role in valence processing, 2) Profile the transcriptome of this circuit component, 3) Select for surface receptors or other druggable targets, 4) Determine the contribution of this neuromodulatory signal on plasticity, 5) Establish the input-output architecture of the neuromodulatory innervation and postsynaptic, downstream targets, and 6) Establish a causal role for this particular neuromodulatory signal in neural activity and behavior associated with valence processing. The specific hypotheses included in this proposal are: that NT serves to guide plasticity to the appropriate target, that there are parallel circuits that have some local interaction in the BLA, and that NT alters the coding dynamics by increasing signal-to-noise ratio by amplifying signal by modulation of glutamatergic transmission. A successful outcome of this project will provide a specific model for how a neuromodulatory signal such as NT can solve the ?valence assignment problem.?