David Moorman - US grants

The supplementary eye field (SEF) of the macaque monkey is commonly thought to be an oculomotor area. This view is seemingly supported by the fact that SEF neurons fire when monkeys prepare to make eye movements, with each neuron firing preferentially before eye movements to targets within a restricted response field. However, planning eye movements involves remembering the locations of targets and deploying attention to those locations. Thus neuronal activity in the SEF may be related to high-order functions accompanying eye movements rather than to the programming of eye movements in itself. To resolve this issue is the aim of the proposed experiments. Monkeys will be trained to perform both a memory guided saccade task (in which they mast plan eye movements to a remembered location) and a spatial working memory task (in which they must remember a location but suppress any tendency to look at it). In the context of each kind of task, they will be trained to process locations as defined with respect to the retina and with respect to reference objects. During task performance, neuronal activity will be monitored in the SEE The data will be analyzed to test the hypothesis that neurons in the SEF represent locations being held in working memory regardless of whether or not those locations are the targets of intended eye movements. The results will clarify the neural mechanisms underlying spatial working memory and will help to explain the nature of behavioral impairments occurring after mum and in cases of neuropsychiatric disorder with frontal lobe involvement.

DESCRIPTION (provided by applicant): One of the defining characteristics of drug addiction is compulsive drug seeking when it is ineffective or detrimental for the individual to do so. Animal models investigating the neural basis of drug seeking have, until recently, focused little attention on characterizing addiction-related endophenotypes that differentially manifest across individuals. The development of treatments for addiction is dependent on understanding what changes occur in the brains of addicted vs. non-addicted individuals. The goal of the proposed project is to investigate the neural basis of individual differences in compulsive drug seeking. Along with cocaine self-administration, we will employ recently-described behavioral models that use clusters of addiction-related endophenotypes to identify individuals as addict-like or non-addict. In these models, such rats are reliably identified based on how strongly they persist in seeking cocaine under different types of conflict introduced in a battery of tests. The tests and the endophenotypes measured include: progressive ratio (willingness to expend effort), seeking in the presence of a paired aversive stimulus (resistance to negative outcomes), and seeking during a non-drug period (persistence despite known absence of drug). We will focus on differential neuronal adaptations in the prefrontal cortex (PFC). The PFC is consistently implicated in both driving and inhibiting drug seeking in humans and animals, and dysregulation of PFC function is thought to be a major factor in the development of addiction. It is not clear, however, how different regions of this heterogeneous structure (e.g., cingulate, prelimbic, infralimbic, and orbitofrontal cortices in the rat) interact to regulate drug seeking in addicted individuals. To address this issue, we will record the activity of multiple single neurons in each of these four PFC regions simultaneously in rats during both self-administration and performance of the addiction-characterizing tests described above. Rats will be tested and recorded during an early (~2 weeks) and late (~7 weeks) session in order to monitor PFC neural activity related to the onset of addiction endophenotypes. We hypothesize that PFC areas more directly involved in driving drug-seeking behavior (prelimbic and orbitofrontal) will have amplified seeking-related activity in addict-like individuals that strengthens over time. We also hypothesize that PFC regions more involved in inhibiting drug seeking behavior (infralimbic and cingulate) will display a gradual weakening of activity over time in addict-like rats. The dual nature of this plasticity: the strengthening of seeking-related circuits and weakening of inhibition-related circuits is proposed to be a key component of the compulsive drive to obtain drugs in addicts. These studies constitute a novel way to investigate the neural plasticity related to addiction and will produce valuable data addressing potential targets for addiction-specific treatments. .

PROJECT SUMMARY/ABSTRACT Understanding the neural systems specifically driving compulsive drug seeking is essential for developing treatments for addiction as a disease. The orexin/hypocretin (ORX) system in the hypothalamus has been implicated in motivation for natural and drug rewards, in addition to its role in arousal and other physiological functions. This system may play a critical role in the extremely high levels of motivation and craving underlying addiction, but it is unknown how specific populations of ORX neurons contribute to compulsive drug seeking. Different ORX neuron populations may regulate different behavioral or physiological functions based on anatomical location or connectivity. Identification of specific neuron ensembles that selectively regulate compulsive drug seeking will allow the development of treatments for drug craving that do not affect other ORX-mediated functions such as arousal or normal hedonic states. Here we will investigate the roles of individual ORX neurons in rat models of compulsive drug and natural reward (sucrose) seeking. We will selectively express optogenetic and chemogenetic effectors in ORX neurons to monitor and modulate specific ORX neuron populations during cocaine and sucrose seeking. In Aim 1 we will use multi-neuron ensemble recording combined with optogenetic tagging to characterize the activity of ORX neurons during cocaine and sucrose seeking. In Aim 2 we will selectively modulate either lateral or medial hypothalamic subpopulations of ORX neurons during cocaine and sucrose seeking using designer receptors exclusively activated by designer drugs (DREADDs). The studies will focus on regulated and compulsive models of drug and sucrose seeking to examine changes in ORX function as compulsive drug/reward seeking develops. Based on previous studies and preliminary results we hypothesize that lateral ORX neurons will encode and regulate drug/reward seeking early in regulated seeking, but that medial regions will also be recruited in late-stage compulsive seeking, particularly of cocaine. These studies are the first in a series designed to precisely identify unique functions of specific ORX neuron populations based on a wide range of factors, and to determine their unique contributions to addiction and related compulsive behaviors.

PROJECT SUMMARY/ABSTRACT The orbitofrontal cortex (OFC) has been heavily implicated in reward valuation and seeking, and there is a strong association between OFC dysfunction and addiction to drugs of abuse. Accumulating evidence suggests that OFC may be a critical node in the development of compulsive alcohol seeking in alcohol use disorders. Despite the clear relevance of OFC function to alcohol use, however, there have been few direct studies of this relationship and no studies of OFC neuron function during alcohol seeking. We will investigate OFC function during ethanol expectation, seeking, taking, and consumption, as well as how OFC is disrupted in compulsive ethanol motivation following chronic use. Based on previous results, we expect OFC activity to underlie ethanol preference and motivation and to be upregulated during enhanced motivation in compulsive ethanol use. We will record the activity of OFC neuron ensembles in different groups of rats given either short (~1 month) or long (~4 months) access to ethanol. Both male and female rats will be studied in order to understand how differential OFC function underlies previously described sex differences in ethanol use. In short-access animals, we and others have observed striking individual differences in preference for ethanol. We hypothesize that OFC activity will positively correlate with ethanol motivation and negatively correlate with consumption in this group. In long-access animals, ethanol drinking becomes compulsive ? characterized by increased motivation and resistance to adulteration with quinine, which is normally aversive. We hypothesize that, in punishment-resistant compulsive ethanol seekers, OFC neurons will exhibit pathologically enhanced activation during ethanol cues and seeking and diminished inhibition during consumption. In both studies, we will also manipulate OFC activity to assess a causal relationship between OFC and ethanol use. We hypothesize that OFC inhibition will decrease preference and motivation for ethanol. These studies will provide new information regarding the specific ethanol-related behaviors driven by OFC activation as well as mechanisms underlying susceptibility for excessive drinking and problematic alcohol use. By drawing direct connections between OFC function and the transition to compulsive alcohol seeking, these studies have a strong potential to identify an important new target for treatment of alcohol use disorders. The two Specific Aims to be investigated in this project are: 1. Identify OFC signals related to individual differences in behavioral components of ethanol use using Pavlovian and operant tests of ethanol expectation and seeking in short-access rats. We will probe the relationship between OFC function and ethanol motivation focusing on individual and sex differences in behavior. 2. Identify OFC signals related to compulsive motivation for alcohol using the same tests in long-access rats who demonstrate elevated, punishment-resistant ethanol seeking. We will probe how OFC activity related to ethanol seeking and consumption is enhanced or suppressed after chronic ethanol use.

PROJECT SUMMARY A history of heavy alcohol and a history of stress both independently increase the risk of Alzheimer's disease related dementia, including early onset dementia. We propose that high alcohol consumption facilitates the onset of, or exacerbates the severity of, Alzheimer's disease pathology specifically in the brainstem nucleus locus coeruleus (LC). The basic research that defines which aspects of Alzheimer's disease related pathology are driven by alcohol and how, remains unknown. The pathological changes that lead to Alzheimer's disease are known to occur decades before symptoms arise. One of the earliest changes in the central nervous system is tau hyperphosphorylation and cellular dysfunction within LC. LC pathology is a ubiquitous finding of post- mortem Alzheimer's disease. Given the established relationship between LC pathology and sporadic Alzheimer's disease, agents that promote pathology within LC likely promote Alzheimer's risk. In our parent grant we look at the impact of alcohol and stress on LC function in young animals, we have established that high alcohol drinking mice and monkeys also demonstrate cognitive dysfunction. The goal of this supplement is to investigate how alcohol and stress history that drives elevated drinking contributes to Alzheimer's related pathology in middle aged animals. Our central hypothesis is that elevated drinking in response to alcohol and stress history also promotes early onset Alzheimer's-like pathology in the LC. We will evaluate this hypothesis across sexes and species using rodents and non-human primates. We will investigate the relationship between alcohol dose, changes in cognition and Alzheimer's disease-like pathology in LC. We will compare age- matched controls to alcohol and stress exposed animals and look at individual differences in alcohol intake, cognition and Alzheimer's related pathology. A histopathological battery of markers will be used to evaluate LC integrity, measuring oxidative stress, autophagy, apoptosis, hyperphosphorylated tau, adrenergic receptor expression and unbiased stereological counts of LC from macaques and mice with varying alcohol dose histories. In both species we will analyze the relationship between prior alcohol intake, cognition, and pathology to identify behavioral predictors indicative of risk for Alzheimer's-like pathology. These aims will answer pressing questions on the relationship between alcohol intake and Alzheimer's disease. Cross-species analysis and markers back translated from human Alzheimer's samples enhance the clinical relevance of our findings. Our results will inform future diagnostic and early intervention strategies for Alzheimer's disease in the context of alcohol use disorder.

Brain science will benefit from the capabilities in tracing complex animal behaviors down to ensembles of individual neurons, and moreover establishing a real-time closed-loop brain-interface, ideally with deep brain access in a free-moving animal. This research project aims to address the focus areas in this National Science Foundation program by merging novel neurotechnology, evaluation of neural circuits during performance of complex cognitive behaviors, and large-scale neuron ensemble analysis and closed-loop behavioral control. The outcome of this research will result in new technologies and computational tools that can be used across the field of neuroscience and behavior, strengthening research efforts of multiple research groups. The educational objectives of this proposal are aimed at training and inspiring young engineers and scientists who are equipped with the multidisciplinary background required to help define the future trajectory of brain interfaces and data sciences. The broader impacts of this project include: 1) advancing transformative device technologies for next-generation neurotechnology and providing new and more powerful tools for neuroscience studies, 2) educating underrepresented undergraduate and graduate researchers to contribute to the nation's workforce needs in biotechnology, 3) contributing to the K-12 science, technology, engineering, and mathematics education through weekend seminars and mentoring student-teacher pairs from local middle/high schools; and 4) promoting neuroscience and neurotechnology among local senior citizens and support groups for neurological diseases.

The research objective of this proposal is to combine high precision optoelectronic neural probes with real-time neural decoding to feedback optogenetic control over animal behavior. Such closed-loop neural interface will establish a generalizable technology platform to study complex animal behaviors using optogenetic tools and real-time learning. The proposed work will open ample research opportunities and form connections among hardware engineering, cognitive neuroscience, and data science. The intellectual merit of the proposed work will be evidenced by three major contributions: 1) demonstration of high-precision optogenetic brain interface that combines multiplexed recording from and bi-directional control over neuron ensembles, 2) demonstration of closed-loop brain interface that employs real-time neural decoding and adaptive learning to control animal behavior, and 3) characterization of complex decision-making using high-precision, multiplexed data linking multiple brain areas.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

PROJECT SUMMARY/ABSTRACT The balance between response execution and response inhibition (i.e., going vs. not-going or stopping) plays a fundamental role in regulating normal behavior, and it is disrupted in many psychiatric diseases associated with impulsivity, including ADHD, OCD, schizophrenia, and substance abuse. Action control is regulated by a number of brain structures, and prefrontal cortex (PFC) plays a particularly prominent role in shaping go vs. no- go or stop decisions. However, the mechanisms of how PFC neurons control this response execution vs. inhibition balance are currently unknown. The projects in this proposal will address this issue by testing a number of hypotheses related to the dynamic nature of PFC neuron ensembles in behavior control. The overarching hypothesis to be tested is that separate ensembles of PFC neurons, distributed across multiple PFC subregions are defined by the intersection between 1) diverging connectivity with downstream targets, and 2) selective activation with precise temporal dynamics during either action initiation or action suppression. We will study PFC ensemble contributions in rats performing a novel Go/NoGo task designed to specifically extract information related to action decisions. In Aim 1 we will use new calcium integrator tools to identify task-activated ensembles of neurons, map their efferent connectivity, and optogenetically manipulate them, thereby demonstrating a causal role for neuron populations defined by temporal co-activation anatomical features in regulating action control. In Aim 2, we will identify the specific temporal dynamics of action-specific ensembles through large-scale cellular neurophysiological recording across the PFC and will identify how anatomically-defined ensembles are differentially activated using optogenetics-paired ensemble neurophysiology. The results from these studies will provide key evidence supporting or refuting the hypothesis that PFC neuron ensembles, aligned into groups via temporally correlated activity and anatomical connectivity, regulate decisions to initiate or withhold behaviors. The results from these studies will also provide a launchpad for future work investigating additional anatomical, molecular, and genetic identities of neural ensembles related to response selection, both within PFC and in other associated structures. In addition to significantly advancing our understanding of executive control, these and future studies will identify novel treatments for mental diseases involving impulsivity and other aspects of disrupted response selection based on the intersection of circuitry, molecular identity, and physiology.