Christopher J. Pittenger - US grants

Different forms of memory employ different logical, serve different behavioral roles, and are associated with different neuroanatomical structures, but appear to use similar mechanisms of information storage. Specifically, memories are believed to e stored in plastic change in the connections between neurons. Abnormalities of synaptic plasticity have been suggested in the etiology of retardation, drug addiction, depression, and other pathological states. Synaptic plasticity, as well as many forms of learning, has an early and late phase; the late phase requires gene activation. The transcription CREB has been implicated as a major player in the induction of the genes required for long-lasting, late-phase plasticity. I have generated transgenic mice which expressing a dominant- negative allele of CREB, which interferes with its function in the induction of downstream genes. In one transgenic line, expression of the transgene is largely restricted to the CA1 region of the dorsal hippocampus; plasticity in this region has been strongly implicated in the learning of behavioral tasks. I have shown that mice of the line are deficient in the acquisition of spatial memory but not in a control task. A second line of mice expresses the transgene exclusively in the dorsal striatum, a structure that is required for the learning of certain habit-based tasks. These mice are deficient in two such tasks but not in hippocampus- dependent learning. Future studies under this fellowship will further explore the behavioral phenotype of these two lines of mice further characterize the molecular consequences of interfering with CREB function, and (in collaboration with others) investigate the electrophysiological correlates of these observed behavioral deficits. These studies will lead to an increased understanding of the mechanisms of different forms of learning in normal and pathological conditions.

[unreadable] DESCRIPTION (provided by applicant): Many of our actions feel automatic. Driving a familiar route to work 'on autopilot' is a common experience - as is taking a wrong turn when today's goal differs from the norm. This is an example of habit learning - a pattern of associations between stimuli and responses, or between patterns of thought, that is acquired over time and, once acquired, become stereotyped and requires effort to overcome. Dysregulation of such habit learning, and of the basal ganglia circuitry that underlies it, is central to obsessive-compulsive disorder, Tourette's syndrome, and related disorders. The mechanisms of habit learning may be of importance to more than one psychiatric disorder. Unfortunately, our knowledge of the mechanisms of information processing and storage in the basal ganglia during striatum-dependent learning remains rudimentary. Targeted genetic manipulations in mice have been a useful tool in the analysis of other forms of learning. We have recently shown regulation by the transcription factor CREB to be critical in normal striatum- dependent learning, using transgenic mice in which CREB's function is specifically disrupted in the striatum. This study represents the first time, to our knowledge, that such specific targeting of the striatum in genetically modified mice has been used to probe the mechanisms of striatum-dependent learning. We now propose to build on this preliminary study through more refined behavioral assays, targeting subregions of the striatum using viral vectors, and characterizing downstream genes important in striatal information processing and storage. This approach takes advantage of my experience in the generation and behavioral analysis of genetically modified mice as well as other experimental approaches in which expertise exists in the Yale community. Clinical expertise in the Yale OCD Research Clinic and Child Study Center allows for a clinically informed research program that will aid me in my development towards independence as a researcher while advancing our understanding of psychiatric disorders in which maladaptive habits wreak havoc in patient's lives. This understanding will pave the way for therapies of the future. PUBLIC HEALTH RELEVANCE: Obsessive-compulsive disorder is the fourth most common psychiatric disorder and a major cause of disability in America and worldwide. The neural circuitry that underlies it is involved in normal habit learning. We seek to understand the mechanisms of this habit learning and of OCD. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Targeting glutamate in OCD: a placebo-controlled, double-blind augmentation trial of the glutamate-modulating agent riluzole in treatment-refractory OCD. Obsessive-compulsive disorder (OCD) affects approximately 2.5% of the population worldwide. About a quarter of patients have symptoms that are resistant to available medications and psychotherapeutic approaches. Many of those described as `responders'to existing treatments suffer substantial residual symptoms and lead constricted lives. New treatment approaches are urgently needed. Several lines of evidence suggest that the ubiquitous amino acid neurotransmitter glutamate may be dysregulated in the brains of patients with OCD. This leads to the hypothesis that medications that target glutamate may represent a novel treatment strategy. The glutamate-modulating medication riluzole, which has been FDA approved for over ten years for use in amyotrophic lateral sclerosis, is one such agent. Preliminary open-label data suggest that a substantial fraction of patients with profoundly treatment-resistant OCD, who suffer severe symptoms and impaired quality of life despite medication and psychological treatment, improve when riluzole is added to their regimen. Importantly, several patients with compulsive hoarding, which is notoriously refractory to current treatments, have responded to pharmacological augmentation with riluzole. These preliminary observations do not provide adequate evidence of the efficacy of riluzole in OCD to justify its general clinical use. A more rigorous, controlled trial is essential. As a step towards this end, and to explore feasibility issues essential to the design of a larger, multi-site trial, this application proposes a pilot placebo-controlled, double-blind trial of riluzole augmentation in OCD. 60 outpatients with treatment-resistant OCD on stable medication regimens will be randomized to receive either riluzole (at the standard dose of 50 mg twice daily) or placebo, following a two-week single-blind placebo lead-in phase. The primary outcome measure will be improvement in Y-BOCS;measures of depression, anxiety, quality of life, and other variables will be analyzed in secondary analyses. In exploratory analyses, we will investigate genetic and clinical variables as potential predictors of response. DNA will be collected from all patients. Exploratory analyses of candidate genes in the serotonin and glutamate systems and of specific dimensions of symptomatology may help identify predictors of treatment response. While this study is not powered to definitively identify the predictors of response to riluzole, it will allow the generation of specific hypotheses to be further explored in a larger future trial. Many patients suffer from treatment-resistant OCD. This trial is a critical step towards exploring the efficacy glutamate modulating agents such as riluzole as a new alternative to alleviate their suffering.

DESCRIPTION (provided by applicant): Animal models of disease pathophysiology are essential tools in the investigation of complex disorders, both testing etiological hypotheses and serving as a platform for the development of novel therapeutic strategies. However, valid and useful animal models of psychiatric conditions have been difficult to develop, because of the complex nature of their symptomatology and their multitudinous and poorly understood causes. Here we propose a new approach to the development of pathophysiologically grounded models of complex psychiatric disease. Rather than base a model on superficial phenotypic resemblance to the symptoms of a disorder, on response to currently used medications, or on putative causative factors of small effect (such as disease-associated alleles of candidate genes), we propose to base a model on recent post-mortem findings. This approach has significant advantages. First, the effect size of abnormalities seen in postmortem studies is necessarily large, because sample size is necessarily small (in contrast to the real but small effects that can be found in huge genetic studies);basing a model on an abnormality of large effect is more likely to produce disease-relevant downstream consequences. Second, the approach is neutral with respect to etiology;insight into the core features of complex disorders can be generated by modeling core pathophysiological features rather than individual hypothesized causes. Finally, the technical approach we have developed allows flexibility in the timing and extent of the neuronal lesion that underlies the model, and is generalizable to other important neurobiological questions and modeling of other psychiatric conditions. We apply this conceptual approach to the modeling of Tourette syndrome (TS) based on neuropathological findings from the Vaccarino lab, which is collaborating on the current studies. In a pair of recent papers they have documented a reduction of certain key populations of interneurons in the striatum, a structure previously implicated in TS. We will use transgenic and viral reagents to produce an equivalent ablation of these interneurons in mice. These animals will then be tested in behavioral analyses of specific relevance to TS, including prepulse inhibition and striatum-dependent procedural learning;the effect of medications with anti- Tourettic efficacy on observed behavioral abnormalities will be investigated. Finally, since the symptomatology of TS typically waxes and wanes over ontogeny, we will probe the developmental trajectory of the effects of interneuronal ablation by inducing it in young animals and assaying behavior in adolescence and adulthood. These studies serve several important purposes. First, they provide proof of concept for an innovative strategy to modeling the pathphysiology of mental illness. Second, they probe a specific hypothesis of TS, and potentially provide a platform for the development of novel therapeutics. Third, consistent with the goals of the B.R.A.I.N.S. RFA, they provide critical support to an innovative young investigator and his efforts to apply new, sophisiticated methodologies to core problems in the biological study of mental illness. PUBLIC HEALTH RELEVANCE: Animal models of the mechanisms of disease are a critical tool for understanding the mechanisms of complex diseases and for developing new therapies;unfortunately, producing useful models of major psychiatric disorders has proven a daunting challenge, and progress has been slow. Here we describe a new strategy to the development of such models of complex brain disorders, by using molecular tools in mice to reproduce the changes found in post-mortem studies of the brains of patients. This approach is developed in the specific case of Tourette syndrome;but the principal and many of the technical aspects of our approach are generalizable to the modeling and investigation of other neuropsychiatric conditions.

DESCRIPTION (provided by applicant): Obsessive-compulsive disorder (OCD) is prevalent and severe, affecting approximately 2% of the population worldwide and producing substantial morbidity even when optimally treated. Serotonin reuptake inhibitors (SRIs) form the mainstay of pharmacotherapy for the disorder;serotonin agonists can exacerbate symptoms;and genetic studies suggest that abnormalities in the serotonin system may contribute to the disorder. However, the nature of any disruption in serotoninergic modulation in OCD remains poorly understood. The 5-HT1B receptor may play a critical role in this regard: the 5-HT1B/1D agonist sumatriptan has been shown to exacerbate OCD symptoms in several studies;and a number of genetic investigations have provided suggestive evidence that a polymorphism in the 5-HT1B gene is associated with OCD risk. 5-HT1B agonists disrupt prepulse inhibition (PPI), a measure of sensorimotor gating that is attenuated in OCD (as well as in several other neuropsychiatric conditions), in animals;and this disruption is ameliorated by chronic treatment with SSRIs - which is standard treatment for OCD. We hypothesize that functional abnormalities of the 5-HT1B receptor contribute to OCD. Measurement of this receptor in vivo in humans has been impossible until very recently, with the development and characterization at Yale of a novel positron emission tomography (PET) ligand, [11C] P943, with nanomolar affinity and good specificity for the 5-HT1B receptor. We propose to image 5-HT1B receptors by [11C] P943 PET in 15 medication-free, non-depressed OCD patients and 15 matched controls. This PET investigation will be enhanced by linking it to two OCD-relevant functional measures. First, we will assess symptom severity in all patients, using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). The Y-BOCS was developed in our clinic in the 1980s and remains the gold-standard instrument for rating OCD symptoms. Second, we will assess PPI in all patients and controls. PPI has been shown to be blunted in patients with OCD. While it is not specific - it is also blunted in Tourette syndrome and schizophrenia, among other conditions - it is unique among candidate OCD endophenotypes in that it has been shown, in studies in animals, to be impaired by 5-HT1B agonists. This leads us to hypothesize that 5-HT1B receptor abnormalties may be linked to both OCD symptomatology and to blunted PPI;we expect PPI to correlate negatively with 5- HT1B binding potential. By investigating the 5-HT1B receptor in vivo in humans with OCD and seeking to correlate it with functional measures, we believe that this study will provide important new insight into the dysregulation of serotoninergic neurotransmission in this disorder. This investigation will thereby inform neurobiological models of this prevalent disorder. Through such advances, new treatments can be developed to aid the substantial minority of patients who receive little benefit from existing therapies. PUBLIC HEALTH RELEVANCE: Obsessive-compulsive disorder (OCD) is common and leads to profound suffering;it can be treated with medications that target serotonin, but many patients get little benefit from this or other established treatments. We will examine a particular brain receptor for serotonin, the 5-HT1B receptor, in the brains of patients with OCD, using positron emission tomography. Better understanding of abnormalities in the serotonin system in OCD will pave the way for new pharmacological treatments of this severe neuropsychiatric disorder.

DESCRIPTION (provided by applicant): Animal models of disease pathophysiology are essential tools in the investigation of complex disorders, both testing etiological hypotheses and serving as a platform for the development of novel therapeutic strategies. However, valid and useful animal models of psychiatric conditions have been difficult to develop, because of the complex nature of their symptomatology and their multitudinous and poorly understood causes. Here we propose a new approach to the development of pathophysiologically grounded models of complex psychiatric disease. Rather than base a model on superficial phenotypic resemblance to the symptoms of a disorder, on response to currently used medications, or on putative causative factors of small effect (such as disease-associated alleles of candidate genes), we propose to base a model on recent post-mortem findings. This approach has significant advantages. First, the effect size of abnormalities seen in postmortem studies is necessarily large, because sample size is necessarily small (in contrast to the real but small effects that can be found in huge genetic studies); basing a model on an abnormality of large effect is more likely to produce disease-relevant downstream consequences. Second, the approach is neutral with respect to etiology; insight into the core features of complex disorders can be generated by modeling core pathophysiological features rather than individual hypothesized causes. Finally, the technical approach we have developed allows flexibility in the timing and extent of the neuronal lesion that underlies the model, and is generalizable to other important neurobiological questions and modeling of other psychiatric conditions. We apply this conceptual approach to the modeling of Tourette syndrome (TS) based on neuropathological findings from the Vaccarino lab, which is collaborating on the current studies. In a pair of recent papers they have documented a reduction of certain key populations of interneurons in the striatum, a structure previously implicated in TS. We will use transgenic and viral reagents to produce an equivalent ablation of these interneurons in mice. These animals will then be tested in behavioral analyses of specific relevance to TS, including prepulse inhibition and striatum-dependent procedural learning; the effect of medications with anti- Tourettic efficacy on observed behavioral abnormalities will be investigated. Finally, since the symptomatology of TS typically waxes and wanes over ontogeny, we will probe the developmental trajectory of the effects of interneuronal ablation by inducing it in young animals and assaying behavior in adolescence and adulthood. These studies serve several important purposes. First, they provide proof of concept for an innovative strategy to modeling the pathphysiology of mental illness. Second, they probe a specific hypothesis of TS, and potentially provide a platform for the development of novel therapeutics. Third, consistent with the goals of the B.R.A.I.N.S. RFA, they provide critical support to an innovative young investigator and his efforts to apply new, sophisiticated methodologies to core problems in the biological study of mental illness.

DESCRIPTION (provided by applicant): Obsessive-compulsive disorder affects 2% of the population and produces substantial morbidity worldwide. It is often unresponsive even to optimal psychotherapy and pharmacotherapy. New insights into the neurobiology of the disorder, and the pharmacological strategies to which they may lead, are urgently needed. Convergent evidence suggest that dysregulation of the neurotransmitter glutamate may contribute to OCD; glutamate-modulating medications may therefore be of benefit in some of the 30% of cases refractory to standard treatment. Genetic associations and cerebrospinal fluid (CSF) findings supporting this hypothesis have been reported, by our group and others. Magnetic resonance spectroscopy (MRS) allows noninvasive measurement of glutamate in defined anatomical regions and thus offers the unique capacity to investigate dysregulation of the neurotransmitter in the specific circuit associated with OCD symptomatology. MRS studies have suggested glutamate abnormalities in the anterior cingulate cortex (ACC), the striatum, and the orbitofrontal cortex. However, these studies have been performed at low field strength and have been unable to dissociate glutamate from glutamine (reporting instead a compound measure, Glx, and have not generally replicated one another. The clarity possible through state-of-the-art glutamate measures at higher field strength is badly needed to refine our understanding of glutamate dysregulation in OCD. We here report a pilot study measuring glutamate and glutamine in the anterior cingulate cortex. Spectral fitting using a simulated basis set on data collected from a single midline voxel over the ACC in a 4T MRS scanner revealed reduced glutamate, but normal glutamine, only in euthymic OCD patients. Depressed OCD patients had normal glutamate levels. This unexpected effect suggests a pathophysiological interaction between these frequently comorbid disorders. It also may be a source of variability contributing to the failures of replication among published reports of Glx. We propose to replicate and expand these findings. First, we will replicate our pilot study in a larger cohort, tis time also including unmedicated depressed patients as a comparison group to better elucidate the interaction between diagnoses. Second, we will perform glutamate and glutamine measures in the striatum, another structure implicated in OCD in which Glx abnormalities (elevations, in this case) have been inconsistently reported. We will then investigate the ability of these measurements of brain neurochemistry to predict the response to pharmacotherapy; such an association would identify glutamate measures as a potential clinically useful biomarker to help guide therapeutic choices. This series of state-of-the-art spectroscopic investigations will elucidate the region-specific dysregulation of excitatory neurotransmission in OCD, importantly refining our understanding of the neurochemistry of the disorder while probing the potential utility of a novel and potentially clinically useful biomarker. PUBLIC HEALTH RELEVANCE: Obsessive-compulsive disorder (OCD) is common, is often severe, and is inadequately treated with available approaches; several lines of evidence suggest that the neurotransmitter glutamate may be disrupted in this disorder. We use magnetic resonance spectroscopy (MRS) to investigate levels of glutamate and related neurotransmitters in patients, in vivo, in brain regions known to be associated OCD, to better understand how disruption of glutamate-based neuronal signaling may contribute to the disorder. We then investigate how these abnormalities in glutamate may predict treatment response, with the ultimate aim of providing a new clinical tool to guide the selection of therapy.

ABSTRACT The basal ganglia circuitry ? including the primary input nucleus, the striatum ? critically regulates numerous behavioral processes and is implicated in the pathophysiology of multiple neuropsychiatric conditions, including Tourette syndrome (TS) and obsessive-compulsive disorder (OCD). Regulation of the basal ganglia by the modulatory neurotransmitter dopamine (DA) has been extensively studied. Much less is known about the regulation of this circuitry by histamine (HA). Recent findings have highlighted the contribution of dysregulated HA modulation of the basal ganglia to neuropsychiatric disease, especially TS and OCD. A mutation in histidine decarboxylase (Hdc), the key biosynthetic enzyme required for HA production, was identified as a rare cause of TS and, with lower penetrance, of OCD. Our studies in Hdc knockout mice confirm that HA disruption can lead to TS-relevant behaviors and changes in striatal neurochemistry and function. Preliminary data from the mouse model focus attention on the histamine receptor H3R, which is highly expressed in the striatum. Signaling by H3R in the basal ganglia is not well understood. Recent work, most of it ex vivo, has documented heterodimerization between H3R and both D1R and D2R dopamine receptors and shown that H3R and D1R interact in counterintuitive ways in the regulation of MAPK. Such heterodimerization of G- protein-coupled receptors is increasingly reported, but its functional significance has been difficult to pin down. We have replicated H3R-D1R functional interactions in vivo and identified a behavioral correlate. We have also identified a novel, cell-type specific effect of H3R on signaling through AKT-GSK3?: in striatal medium spiny neurons that express D1R (D1R-MSNs), H3R leads to phosphorylation (and thus inactivation) of GSK3?, while in D2R-MSNs it leads to GSK3? dephosphorylation. This differential regulation of both MAPK and GSK3? highlights the ability of H3R-DR functional interactions to modulate signaling and the importance of better understanding this dimension of striatal regulation. We propose to use existing transgenic mouse lines to characterize functional interactions between H3R and dopamine receptors in D1R- and D2R-MSNs of the dorsal striatum. We predict nonlinear interactions in the regulation of both MAPK and GSK3?, and that these will lead to interactions in the regulation of locomotor activity. We will test the causal importance of H3Rs in specific striatal cell types by generating inducible H3R knockout mice, which we will cross with cell type-specific cre-expressing transgenic mice to produce D1R- and D2R-MSN-specific disruption of H3R signaling. We predict differential effects at the level of both signaling and behavior when H3R is disrupted in different MSN subtypes. These experiments will shed new light on the underappreciated role of HA in the modulation of basal ganglia function and lay the groundwork for future studies in animal models of pathophysiology.

ABSTRACT Tourette syndrome (TS) and other tic disorders affect up to 5% of the population and are frequently comorbid with other neuropsychiatric conditions. Their neurobiology is poorly understood, and current treatments are often inefficacious. Recent genetic findings implicate dysregulation of histamine (HA) signaling as a rare cause; in a recent paper in Neuron we established the HA-deficient histidine decarboxylase (Hdc) knockout mouse as a model of tic pathophysiology that has etiologic, face, and predictive validity. Convergent evidence implicates the cortico-basal ganglia circuitry in tic disorders. In particular, dysregulation of dopamine (DA) in the striatum is thought to be an important contributing factor. HA receptors are highly expressed in the basal ganglia circuitry. HA regulates DA levels in the striatum: HA infusion in a wild-type mouse reduces striatal DA in vivo, and the HA-deficient Hdc-KO model has elevated basal DA levels. In our first Aim we will elucidate the mechanisms of this poorly understood regulatory interaction. We hypothesize that HA acts on H1R receptors found on inhibitory interneurons in the substantia nigra pars compacta (SNc). We will test this using in vivo pharmacology and microdialysis. We will then test the necessity and sufficiency of HA-induced SNc interneuronal activity for striatal DA regulation, using a novel chemogenetic strategy. Baseline DA dysregulation and repetitive behavioral pathology in the Hdc-KO tic model are subtle, but they are dramatically increased by behavioral or pharmacological perturbations. For example, stress induces repetitive behaviors in the model. Local neuronal disinhibition in the striatum produces a dramatic spike in DA, not seen in WT animals. This suggests a loss of DA homeostasis, rendering the system subject to phasic instability ? a pattern that resembles the phasic phenomenology of tic disorders. We hypothesize that loss of H1R tone on SNc interneurons removes a source of homeostatic regulation; we will test this in our second Aim. We find much more dramatic repetitive behavioral pathology after HA neurons are chemogenetically silenced in vivo. This suggests that mitigating mechanisms constrain behavioral pathology in the KO animal. Identification of such mechanisms is of both basic and translational importance; enhancing them may represent a novel therapeutic strategy, both in tic disorders and in other hyperdopaminergic pathologies. We will arbitrate between two possible explanations for this observation in Aim #3. First, behavioral pathology may be more profound after acute silencing of HA neurons because it also disrupts GABA cotransmission, which is intact in the KO animals. Second, KO animals may develop compensations over ontogeny. We will use a combination of chemogenetics and shRNA knockdown to test these two hypotheses. In the long term, this innovative research program is of both basic and translational importance, aiming to elucidate the normal role of HA in the basal ganglia, establish how its perturbation can lead to tics, and identify potential new treatment targets.

ABSTRACT Tourette syndrome (TS) is a neurodevelopmental disorder, affecting 0.5-1% of the pediatric population, with a marked male predominance. TS is characterized by multiple, recurring tics, which are a source of significant disability. The clinical management of TS poses considerable challenges, partially due to the limited efficacy and numerous side effects of available pharmacotherapies. Tics are triggered and exacerbated by stress, but the underpinnings of this association remain unclear. This proposal seeks to test a novel candidate mechanism whereby stress exacerbates tics, which may represent a new therapeutic target. Over the past few years, the Bortolato lab has shown that neurosteroids, a class of brain-produced steroids that play a central role in the orchestration of stress response, are involved in the neurobiological mechanisms of tic modulation. In particular, our preliminary data in animal models strongly suggest that the adverse effects of stress on tic severity are mediated by the neurosteroid allopregnanolone (AP). The implication of neurosteroids in TS is further suggested by our findings on finasteride, an inhibitor of the key steroidogenic enzymes 5?-reductase 1 (5?R1) and 2 (5?R2). In preliminary clinical trials, this drug led to a significant reduction of tic severity in adult TS patients refractory to standard treatments; furthermore, in animal models of TS, this drug reduced both stereotyped movements and other TS-related behavioral deficits. Although these data are promising, finasteride is contraindicated in childhood due to its demasculinizing effects. Nevertheless, preliminary data in animals suggest that the therapeutic effects of finasteride may be due to 5?R1 inhibition, while the antiandrogenic effects of this drug are primarily due to 5?R2 inactivation. Based on this background, our central hypothesis is that acute stress triggers tics by increasing 5?R1- mediated synthesis of AP. To test this hypothesis, we will use a mouse model of TS firmly grounded in tic pathophysiology, recently developed by the Pittenger group. This model, which reproduces the depletion of striatal cholinergic interneurons observed in post-mortem samples of subjects with severe TS, is particularly well-suited to test our hypothesis, since it exhibits tic-like behaviors in response to stress. The central hypothesis will be tested in two aims, to study how AP (Aim 1) and 5?R1 (Aim 2) contribute to the tic-like responses induced by stress in this model. The proposed research will be the first to test a specific mechanistic hypothesis explaining how acute stress exacerbates tics in TS. If our hypotheses are confirmed, these experiments may lead to a novel therapeutic approach for tics, since highly specific 5?R1 inhibitors have already been developed for clinical use and have excellent tolerability. Furthermore, because neurosteroids modulate the neuroactive functions of sex hormones, a better understanding of their role in tic genesis may help explain the male predominance of TS.

7. Project Summary Decision making in the real world is complex and is modulated by numerous factors. We and others have found that specific aspects of decision making are abnormal in individuals with obsessive-compulsive disorder (OCD). We hypothesize that these abnormalities are related to both dysfunctions in neural cortico-basal ganglia circuits and the development of clinical symptomatology in such domains as indecisiveness, behavioral inflexibility, and compulsive repetition of actions. OCD affects about 1 person in 40; obsessions and compulsions are found in many more. Elucidating their relationship to underlying neurocognitive abnormalities is of fundamental importance and may ultimately lead to diagnostic clarification and new therapeutic interventions. This proposal seeks to employ the computational drift diffusion model (DDM) framework to refine and quantify the cortico-basal ganglia theory of OCD, which is widely accepted but remains qualitative. We employ the ?hold- your-horses? model of subthalamic nucleus (STN) function to characterize individual variation in responses to changes in task difficulty and task context, on both behavioral and neurobiological levels, and their relations to OCD symptomatology. The model suggests that STN activity and connectivity contribute to individual ability to adjust the process of decision formation to meet current task demands, by modulating how much evidence needs to be accumulated before a choice between alternatives is made. This contributes to behavioral flexibility; we expect this STN function to be abnormal in OCD. Consistent with this hypothesis, prior studies and our pilot data suggest that individuals with OCD require more evidence before they make a perceptual categorization decision, which may lead to indecisiveness; but they tend to accumulate less evidence before making an value-based decision (when asked to choose which of two options is preferred), which may lead to reduced response inhibition and poor quality decisions (such as we have previously documented). Differences in decision making across these two contexts have rarely been systematically investigated (and never in OCD). Our novel task allows direct comparison of perceptual and value-based decisions, while varying tasks difficulty, using the rigorous DDM- based analysis on both behavioral and neural levels. Our pilot data demonstrate the feasibility of our approach. This proposal combines a novel theoretical framework of neurocognitive abnormalities in OCD, a sophisticated computational approach, and a specific mechanistic hypothesis implicating the STN and associated networks in OCD pathophysiology. These will be tested using hierarchical Bayesian estimation of DDM parameters in conjunction with state-of-the-art fMRI analyses. Quantifying STN abnormalities with DDM will help us to disentangle OCD-related abnormalities in basic neurocognitive processes and to begin to place the cortico-basal ganglia model of OCD on a more quantitative footing. In future work these analyses can be applied transdiagnostically. Ultimately, we hope this work will produce biomarkers of pharmacological treatment response, and may contribute to novel therapeutics modulating the implicated circuitries.

Project Summary Effective decision making across contexts is essential for successful navigation of a complex world. Decision making styles vary greatly between individuals, and with context and state. Theyy are altered in a range of psychopathologies. However, the development of a systematic understanding of variation in decision making has been hampered by variable and limited characterization of decision-making parameters, small samples in most individual studies, and a lack of robust normative data. Computational models of decision making, such as the drift-diffusion model (DDM), can be fitted to behavioral data from individual participants to reveal variation in underlying processes. Parameters of such computational models may serve as ?cleaner? measures of processes of interest than unmodeled behavioral data, or self-report measures. They can also be used as correlates of neural activation patterns during decision making. The validation of computational models and the identification of model parameters that correlate robustly with brain activation sets the stage for parallel studies in animals, in which causal relations can be more readily probed. We propose to conduct a large-scale online data collection of two DDM-compatible tasks, which probe perceptual and value-based decision-making processes. We will use best practices developed for Amazon Mechanical Turk (MTurk) to generate a reference distribution of DDM parameters. Since DDM relies on precise measurements of reaction time, it is critically important to establish validity of online instruments, which we propose to do by collecting parallel in-lab and online data in an initial medium size sample; this will permit robust hypothesis-driven and exploratory analyses, as well as allowing us to optimize and validate online data collection for the collection of online-only data in a larger sample (N = 500). If successful, this validation will allow large-scale behavioral data collection powered to detect small to medium effect size associations and will provide a reference distribution and cutoff levels for extreme cases of DDM parameters. We will investigate relations between continuous measures of selected clinical tendencies in general population and DDM parameters in a large sample. We will also investigate relations between DDM parameters and individual approach and avoidance tendencies, which are hypothesized to underlie individual variations in decision making styles and have been translationally validated. This will generate new hypotheses as to the role of decision-making abnormalities in psychopathology. The use of computational modeling approaches like DDM and large general population samples may be more powerful for the elucidation of such relationships than simple correlations of behavioral measures with symptomatology. This approach is consistent with the RDoC framework and can be extended in future work to transdiagnostic and translational studies of psychopathology.

ABSTRACT Obsessions and compulsions affect ~30% of the population; when they become severe they lead to a diagnosis of obsessive-compulsive disorder (OCD), which affects one person in 40. Available treatments, including pharmacotherapy with the selective serotonin reuptake inhibitor (SSRI) antidepressants and specialized psychotherapy, are of benefit to many, but individualized response is heterogeneous and unpredictable. Understanding the brain mechanisms of therapeutic change is urgently needed and may guide the development of new interventions. Ultimately, the ability to predict who will respond to a particular treatment would be a major theoretical and clinical advance, would accelerate deployment of effective treatment, and would thereby greatly reduce morbidity. Early studies using perfusion imaging have hinted that baseline neural markers can predict response to pharmacotherapy. However, these studies have not harnessed modern network-focused analytic methods and have not yielded mechanistic insight or clinical utility. Neuropsychiatric disorders are hypothesized to derive from altered functional brain networks. Resting-state functional connectivity MRI (rs-fcMRI) has emerged as a powerful tool to characterize functional network architecture in humans. We propose to use rs-fcMRI, employing state-of-the-art methodologies pioneered by the Human Connectome Project, to map the relationship between functional neural networks and treatment response in OCD. Specifically, we aim to characterize rs-fcMRI connectivity profiles that map onto treatment-associated changes and that predict response. The feasibility of this project is supported by our pilot data. We focus on first-line SSRI pharmacotherapy with fluoxetine as a tractable first step; future studies will incorporate other treatment modalities, including psychotherapy. We propose an innovative clinical design that dissociates treatment from time effects, which is a major challenge in studies of treatment mechanism. 80 medication-free OCD subjects will be randomized 1:1 to receive fluoxetine treatment starting either immediately or after a 6-week placebo lead-in phase. OCD subjects will undergo imaging at baseline and at 6, 12 and 18 weeks. All subjects will be pooled to identify correlates of symptom improvement. The immediate and delayed treatment groups will be contrasted to dissociate treatment-induced neural changes from the non-specific effects of therapeutic contact (i.e. placebo). 40 matched controls will be scanned once and compared with OCD subjects at baseline, prior to pharmacotherapy, to characterize connectivity alterations in the unmedicated state. Neuroimaging data will be analyzed using whole-brain general linear models (GLMs), including between-group and longitudinal effects to isolate effects of time, effects of drug exposure per se, and correlates of clinical improvement. Baseline imaging data will be examined for treatment response prediction, using both a GLM-based regression and via a recently optimized individual classifier, trained on 75% of the sample and then tested on the remaining 25%. This study will yield a rich multi-modal neuroimaging dataset elucidating the neural correlates of OCD symptomatology and of treatment response. If successful, we will identify network targets for novel treatments and take a major step towards the goal of developing predictive measures in the service of precision medicine in psychiatry.

ABSTRACT Childhood-onset OCD is common, affecting 1-4% of youth, and causes profound morbidity. In some cases, symptom onset is remarkably rapid, even overnight. This striking presentation suggests a unique pathophysiology; the syndrome has been called ?pediatric acute-onset neuropsychiatric disorder?, or PANS. Onset is often temporally associated with inflammatory illness, suggesting a neuroimmune mechanism, and immune-modulating treatments are sometimes used. However, pathophysiological details have been difficult to pin down, and the diagnostic landscape remains unclear. One specific etiopathophysiological hypothesis is that infectious illness can, in a susceptible host, lead to the production of antibodies cross-reactive with brain antigens. Consequent brain inflammation is proposed to produce neural dysfunction and clinical phenomenology; an analogy is sometimes drawn to Sydenham?s chorea, in which a similar antibody-mediated pathophysiology has been more clearly demonstrated. This proposal implies that there should be pathogenic antibodies in patients that are not found in controls. A number of studies have sought to characterize such antibodies, and reports have been published of antibodies reactive with D1R and D2R dopamine receptors, tubulin, and other antigens; but non-replication is common in this literature, and it remains unclear what antibodies, if any, contribute to disease. Identification of antibodies clearly associated with symptom onset or severity in PANS, or in any subset of PANS patients, would go far to clarify pathophysiology and diagnostic complexity in this population. With this goal in mind, we investigated antibody binding using a novel in vivo assay in mice. Rather than focusing on specific molecular targets, as most previous studies have done, we sought to examine cellular targets of illness-associated antibodies; and we did so in intact tissue, rather than in reduced systems. In recently published work we described elevated binding to cholinergic interneurons (CINs) in the striatum by antibodies from patients with pediatric autoimmune disorder associated with Streptococcus, or PANDAS, a narrower diagnosis related to PANS.9 CINS have previously been implicated in the pathophysiology of tic disorders and OCD, in post-mortem and preclinical work from our group and others. The suggestion that antibody binding to these interneurons may contribute to pathophysiology thus has immediate plausibility and merits further investigation. In unpublished pilot data we have reproduced this finding using a more efficient ex vivo assay and replicated it in a second small cohort of PANDAS patients. We now propose to replicate, refine, or refute the provocative finding from these pilot data by examining a larger cohort of patients. We will continue to focus on patients with PANDAS in order to limit clinical heterogeneity, but we will examine patients from three different clinical cohorts across two sites (NIMH and the Stanford PANS Clinic) to clarify the generalizability of the findings from our pilot studies. We will examine a total of N = 38 patients and 38 matched controls; when combined with our pilot studies, we will have a total of N = 49 PANDAS patients, which allow well-powered examination of correlation of CIN binding with symptom severity and other clinical variables. If our pilot findings are upheld, this will set the stage for future experiments examining more heterogeneous clinical samples.

ABSTRACT This K24 Mid-Career Investigator Career Development Award seeks support for training and mentorship for Christopher Pittenger, MD, Ph.D., a well-established, tenured Associate Professor in Psychiatry at Yale University, Director of the Yale OCD Research Clinic, and Assistant Chair for Translational Research in the Department of Psychiatry. Dr. Pittenger leads a robust patient-oriented research (POR) research program, which is integrated with his basic/translational lab-based research and has produced important new insights into the neurobiological underpinnings and novel treatment avenues for obsessive-compulsive disorder (OCD) and Tourette syndrome (TS). Dr. Pittenger has a long-standing commitment to mentorship; most notably, he is Co-Director of the Neuroscience Research Training Program (NRTP), the research track within the Yale psychiatry residency. The training plan supported by this grant will allow Dr. Pittenger to increase his skills in quantitative analysis, with a focus on advanced statistical methods and on the design and analysis of fMRI studies. These are areas in which he already has active research with expert collaborators; the aim of the proposed training plan is to enhance his own proficiency to make him a more effective collaborator and mentor in these important domains. Additional training is focused on his own abilities as a mentor and leader, with the goal of increasing his efficacy in the management of his own research groups and in effective and individualized mentorship. These training activities will take place in the context of two NIMH- funded research studies. The first, R01 MH116038, is a recently funded grant on which Dr. Pittenger is co-PI with his close collaborator Alan Anticevic and deploys cutting-edge imaging technology and data analysis approaches to examine brain network connectivity parallels and predictors of therapeutic response to pharmacotherapy in OCD. The second, R01 MH100068, is a grant with collaborator Michelle Hampson that is developing real-time fMRI neurofeedback as a probe and potential treatment for OCD, with promising early results. These two exciting projects provide a fruitful vehicle for the proposed training in statistics and neuroimaging. Dr. Pittenger will devote substantial time to mentoring under this award. One major focus will be the NRTP; the plan is for him to take over as Director of this program over the next few years, and to take the lead in the next resubmission of our T32 grant in 2022. Support of this increased mentorship effort is a second major motivation for the current application. Dr. Pittenger will also provide mentorship to students, postdocs, and junior faculty in his own research program and throughout the Department of Psychiatry Together, these integrated plans for training, research, and mentorship will support a well-established mid-career investigator whose robust research program is producing important insights into the neurobiology and treatment of OCD and TS, and whose dedicated mentorship efforts are helping to establish a new generation of translationally grounded patient-oriented researchers in psychiatric neuroscience.

Project Summary Clinical Neuroscience Research Training Program (CNRTP) in Psychiatry This training program, now in its 20th year, is designed to meet the national goal of increasing the number of fully trained psychiatric physician-scientists conducting clinical and translational patient-oriented research in mental health. In order to be effective independent investigators, psychiatric physician-scientists must be fully trained in both clinical neuroscience and modern clinical-translational research methodologies. The ever-increasing complexity of the science and methods require that individuals receive specialized training in order to take full advantage of the rapid advances occurring in the field. This 2-3 year program will utilize a curriculum designed to give the trainee mastery of the fundamentals of basic molecular and cellular neurobiology, neuropharmacology, neuroimaging, psychiatric genetics and the responsible conduct of psychiatric research in human subjects. Trainees will benefit from individualized mentorship by members of a large and multidisciplinary group of research training faculty within the Department of Psychiatry. The rich training environment is supported by a number nationally funded research programs / infrastructures within the Department of Psychiatry, including the: 1) Clinical Neuroscience Research Unit, 2) National Center for Neurobiological Study of Post-Traumatic Stress Disorder, 4) Center for the Translational Neuroscience of Alcoholism, 5) The Yale Stress Center, 6) Neurobiological Studies Unit, 7) Neuroimaging Program (that includes PET, SPECT, fMRI, MRS, and DTI), 8) Psychotherapy Development Research Center, 9) Program in Human Psychiatric Genetics, as well as 10) new programs in Interventional Psychiatry, Computational Psychiatry, and Diet/Metabolism/Brain-Gut interactions. Trainees will conduct their research studies in specialized inpatient and outpatient research facilities and specialty clinics, and the resources from other basic science programs within the Department and Medical School will also be utilized. For the past 60 years, the Research Faculty in the Department, and its alumni, have had an outstanding track record of training nationally and internationally prominent researchers in psychiatry. The renewal of this application seeks stipends for 5 postdoctoral fellows per year and will allow this program to continue to succeed in increasing the number of fully trained, clinical-translational, patient-oriented research psychiatrists nationally.

Project Summary Declines in the numbers of physicians pursuing careers in patient-oriented research have raised national concerns about an impending crisis in public health care. While numerous medical fields are affected, the problem in psychiatry is particularly acute, with projected shortages prompting an analysis of the problem by the Institute of Medicine. Ironically, shortages of psychiatrists pursuing patient-oriented research careers occur at a time when discoveries in the fields of genetics and neuroscience are having an unprecedented impact on our understanding of behavior. Translating such basic science insights into discoveries in the patient-care realm will ne crucial for improving out understanding and treatment of several mental illnesses. The current R25 renewal is intended to further address the current crisis in mental heath research education through several specific aims, aims that build upon prior success of the past 10 years. These include 1) continuing to educate psychiatry residents under established (?traditional?) model of Intergrated Mentored Patient-Oriented Research Training (IMPORT), 2) building upon this model through the addition of a modified (?early immersion?) track that is designed to better accommodate trainees with greater research experience and respond to increasingly complex translational research methods, and 3) augmenting both models by the addition of early (PG1) elective time, mentoring committees, educational experiences in grant writing (including opportunities for securing pilot funding), and enhanced recruitment. If successfully renewed, the program will continue to benefit the nation, through the increased identification, recruitment and retention of a highly skilled cadre of patient-oriented psychiatric physician scientists, and by piloting and implementing a flexible, individualized model of research education for psychiatry residency programs nationally.