Gregory J. Quirk - US grants

Pursuit of reward and avoidance of threat are two major behavioral motivators. Failure to balance these motivations results in maladaptive decisions and may underlie various pathological conditions. The sustained threat construct of the NIMH Research Domain Criteria (RDoC) includes avoidance, conflict detection, and perseverative behaviors. Sustained threat reactions interfere with the pursuit of rewarding activities that can decrease social interactions and trigger depression. Little is known about how decisions guide behavior during approach-avoidance conflict. The first phase of this MERIT shifted our focus from Pavlovian fear conditioning to active avoidance, exploring how prefrontal-amygdala-striatal circuits express and extinguish active avoidance. For the second MERIT phase, we have developed a new task that maximizes approach-avoidance conflict within a timed cue encounter that pits active avoidance against the pursuit of food. The new approach-avoidance conflict task has revealed three distinct behavioral phenotypes: 1) food-preferring rats that pursue food throughout the tone with little or no avoidance; 2) avoidance-preferring rats which avoid throughout the tone with little or no food-seeking; and 3) timers which seek food early in the tone and avoid later, thereby maximizing both access to food and safety. We will capitalize on these unique behavioral phenotypes to characterize the circuits mediating approach- avoidance decisions, using electrophysiological, immunohistochemical, and optogenetic methods. We will use both male and female rats in all our aims. Aim 1 will use immunohistochemistry combined with electrophysiology and fiber photometry to identify the circuits involved in conflict decision making. Aim 2 will test the circuits identified in Aim 1 with optogenetic manipulations. Aim 3 will assess the power of this task to identify new multi-dimensional behavioral phenotypes integrating conflict strategies with anxiety and social interactions. This research program will enable us to characterize decision-making circuits underlying different strategies for resolving approach-avoidance conflict. RELEVANCE (See instructions): Failure to balance pursuit of reward and avoidance of threat results in maladaptive decisions and pathological conditions including anxiety and depression. Using a novel rodent task that maximizes approach-avoidance conflict, we will characterize the circuits mediating approach-avoidance decisions using electrophysiological, immunohistochemical, and optogenetic methods. This research program will enable us to characterize circuits for resolving approach-avoidance conflict.

[unreadable] DESCRIPTION (provided by applicant): This proposal is for a one-time scientific conference entitled, "Extinction: The Neural Mechanisms of Behavior Change", to be held in Ponce, Puerto Rico, February 2-6, 2005. Extinction is the decreased expression of conditioned responding that occurs when a conditioned stimulus is repeatedly presented in the absence of the unconditioned stimulus. Deficits in extinction learning are thought to underlie anxiety disorders (such as PTSD) and addictive behavior, both of which involve persistent emotional responses that are no longer appropriate. Understanding the neural mechanisms of extinction could lead to novel behavioral and pharmacological therapies. This would be the first conference ever held on the topic of extinction, a new field which has undergone rapid growth in the past 4 years. This is a unique opportunity to bring together the entire field of researchers (32 basic and clinical scientists) to resolve controversies and encourage a translational approach for future research. The conference will consist of 8 sessions: 1) Amygdala mechanisms in extinction of aversive conditioning, 2) Prefrontal mechanisms in extinction of aversive conditioning, 3) Contextual modulation of extinction, 4) Molecular mechanisms of extinction: Prefrontal-amygdala system, 5) Molecular mechanisms of extinction: Other systems, 6) Extinction of appetitive conditioning and addiction, 7) Neural substrate of extinction in humans, 8) Extinction as a therapeutic tool. Each session will be followed by questions from local students and an extended general discussion. Therewill also be evening debates on controversial themes, and a poster session. The conference will have a high degree of women & minority participation at all levels (speakers, organizing committee, attendees), and will provide students in Puerto Rico with unprecedented access to experts in the field. Travel fellowships for students from neighboring countries in Latin America will be provided. The findings will be disseminated in a special issue of the journal Biological Psychiatry, which will reach those most interested in the translational focus of the meeting. Thus, the conference should have considerable scientific impact, as well as serving a capacity-building function in the region. [unreadable] [unreadable]

This proposal addresses a fundamental issue in neuroscience, namely, how do sensory stimuli acquire emotional significance? More specifically, how are fearful responses to stimuli extinguished once the stimuli no longer predict danger? The acquisition of fear associations to aversive stimuli occurs through a form of classical conditioning known as fear conditioning. In auditory fear conditioning, a tone conditioned stimulus (CS) is paired with a footshock unconditioned stimulus (US), resulting in the acquisition of fear responses to the tone such as freezing and response suppression. Fear conditioning depends critically on the amygdala, but less is known about the neural mechanisms of extinction, where unreinforced tones cause fear responses to decrease. Converging data suggests that the ventral medial prefrontal cortex (vmPFC), which projects to the amygdala, is necessary for consolidation of extinction learning. Blockade of NMDA glutamate receptors, which are involved in synaptic plasticity, prevents consolidation of extinction. The central hypothesis of this proposal is that extinction learning requires NMDA-mediated plasticity in prefrontal-amygdala circuits. Using rats, we propose three Aims to test this hypothesis: 1) We will determine the time course of NMDA receptor involvement in consolidation of fear extinction (Hypothesis: Post-training infusion of NMDA antagonists or agonists into the mPFC will impair or facilitate, respectively, extinction memory and neuronal plasticity vmPFC). 2) We will determine the time course of extinction-induced gene expression in mPFC (Hypothesis: Extinction upregulates c-Fos and CREB in the mPFC in an NMDA-deperdent manner), 3) We will determine if strengthening extinction memory with vmPFC stimulation depends on NMDA receptors (Hypothesis: stimulation-induced strengthening of extinction memory will be impaired or enhanced by NMDA antagonists or antagonists, respectively). This proposal combines pharmacological, physiological and molecular approaches to probe the neural mechanisms of fear extinction. Deficits m extinction learning are thought to underlie anxiety disorders such as post-traumatic stress disorder and specific phobia. This research is likely to lead to new methods to strengthen extinction, which could augment extinction-based exposure therapies for these disorders.

DESCRIPTION (provided by applicant): Research on fear learning has transformed the way we think about the etiology and treatment of anxiety disorders such as post-traumatic stress disorder (PTSD). Much of what we know is derived from animal models measuring freezing as a fear response, which resembles exaggerated fear in PTSD sufferers. However people suffering from PTSD also show persistent avoidance of cues associated with their traumatic event. Persistent avoidance interferes with the daily activities, and reduces the opportunity for extinction, thus prolonging PTSD symptoms. Studies in the previous cycle of this grant have shown that the prelimbic prefrontal cortex (PL) drive freezing via projections to the basolateral amygdala (BLA), whereas the infralimbic prefrontal cortex (IL) mediates extinction via projections to inhibitory interneurons within the amygdala. To study avoidance, we have developed a platform-mediated avoidance task (PA) were rats avoid footshock by stepping onto a nearby platform. The platform protects the rat from shock, but also prevents the rat's access to food, similar to clinical avoidance. Furthermore, approximately 30% of rats are unable to extinguish this avoidance response, showing persistent avoidance even after extinction of fear. Preliminary data shows that PL, BLA and the nucleus accumbens (NAc) are necessary for expression of avoidance. However, inactivation of PL and NAc causes rats to revert to freezing behavior. Comparing the effects of manipulations on different behaviors (freezing and avoidance) can help distinguish fear-generating circuits from avoidance-generating circuits. In Aim 1, we will investigate the circuits mediating avoidance using pharmacological, single-unit recording and optogenetic tools. In Aim 2, we will study the neural circuits mediating the extinction of avoidance responses. In Aim 3 we will characterize the neural circuits involved in extinction failure (persistent avoidance). We plan to use optogenetic techniques to silence and/or activate pathways involved in avoidance expression and extinction in order to repair circuits in persistent avoiders.

DESCRIPTION (provided by applicant): Extinction is thought to be deficient in anxiety disorders such as PTSD, and there is a pressing need to translate animal findings in this area to humans. This five-year project represents the continuation of a close collaboration between two sites, one investigating fear extinction in rats (PI: Quirk, Univ. Puerto Rico), and the other in humans (Co-PI: Pitman, MGH-Harvard). Our main goal is to identify homologous structures in the rat and human prefrontal cortex that regulate fear and predict extinction, and to investigate these areas in PTSD. The prelimbic and infralimbic areas in rat prefrontal cortex impair and facilitate recall of extinction, respectively. In the human, the dACC and vmPFC serve similar functions to rat PL and IL, respectively. Our overarching hypothesis is that an imbalance in the activity of these prefrontal areas leads to extinction failure and PTSD. We will investigate these areas in rats and humans in four Specific Aims: 1) To investigate the activity and functional connectivity of rat prelimbic and infralimbic cortex prior to and following extinction of fear conditioning (using multichannel unit recording), and to identify neurobiological markers of extinction failure;2.) To facilitate extinction recall in rats by manipulating this prefrontal network pharmacologically;3) To investigate human homologues dACC and vmPFC in the acquisition and extinction of conditioned fear, and to identify neurobiological markers for extinction failure within these brain regions using PET-FDG and fMRI imaging in healthy humans;4) To characterize the activity of the dACC and vmPFC in PTSD patients and to determine whether neurobiological markers for extinction failure are present in this disorder. We predict that the PL/IL ratio of resting activity in rats, or dACC/vmPFC ratio of resting activity in healthy humans, will be inversely correlated with extinction. In PTSD, we predict that the dACC/vmPFC ratio will be increased and will be correlated with extinction failure. Moreover, we predict hypoactive vmPFC and hyperactive dACC in PTSD patients during extinction retention tests. Exposure therapies that are commonly used to treat anxiety disorders are based on extinction. In addition to elucidating the pathophysiology of PTSD, identifying neurobiological markers of extinction failure could become a screening tool for persons at high risk of trauma exposure. Identifying neurobiological interventions that improve extinction retention could lead to novel treatments for anxiety disorders, mood disorders, and addictions. PUBLIC HEALTH RELEVANCE: Approximately 13% of the adult population in the U.S. suffer from an anxiety disorder, in which it is difficult to control or extinguish fear responses. This proposal will translate findings on the brain mechanisms of extinction from rats to humans, using neuronal recording and functional brain imaging, in order to identify neurobiological markers of extinction success or failure. If successful, this approach could lead to a screening tool for identifying persons at high risk for developing an anxiety disorder and could augment existing extinction-based therapies.

Obsessive compulsive disorder (OCD) is characterized by persistent intrusive thoughts (obsessions) and repetitive intentional behaviors (compulsions). The overall hypothesis of this center is that these symptoms are due, in part, to impaired extinction of fear, which disrupts the normal balance between fear avoidance and reward- seeking. These behaviors depend on medial prefrontal (mPFC)-orbitofrontal (OFC)-basal ganglia circuits, which are known to be dysfunctional in OCD. Deep brain stimulation (DBS) of sites in the ventral capsule/ventral striatum (VS/VS) region reduces OCD symptoms, but the mechanisms are unknown. The VS/VC contains fibers emanating from widespread areas of OFC and mPFC. Therefore, a thorough behavioral mapping of stimulation effects in mPFC, OFC, and VC/VS is needed to optimize electrode placement and understand the mechanisms of therapeutic action of DBS. Project 4 will carry out this mapping. In Aim 1, we will use acute microstimulation to map mPFC and OFC subregions in the expression and extinction of conditioned fear. In Aim 2, we will assess the effects of subchronic microstimulation of OFC and mPFC, and their output axons in the accumbens, in the transfer of fear extinction to instrumental avoidance, using a newly developed behavioral task in rats. By administering the stimulation at various times during training, we will be able to separately evaluate its effects on: 1) extinction learning and retention, 2) the transfer of Pavlovian extinction to instrumental avoidance, and 3) the persistence of avoidance behaviors despite extensive extinction (can microstimulation "cure" the rats by reducing preservative avoidance?) In Aim 3, we will correlate this behavioral mapping with a neural mapping, use immunocytochemical techniques to assess the activation patterns in OFC and mPFC induced by subchronic microstimulation of sites shown to be effective in our task. Mapping the behavioral and neural effects of DBS-like microstimulation in a rodent model will facilitate the translation of rodent circuit models to primates and humans, and could suggest new targets for DBS in OCD. In addition, it will increase our basic understanding of mPFC- OFC interactions, and the role of this network in regulating fear learning and expression. RELEVANCE (See instructions): While deep brain stimulation (DBS) has been shown to be effective in the treatment of OCD, little is known about its mechanisms. Mapping the effects of DBS-like microstimulation in a rodent model could suggest new targets for DBS in OCD. In addition, it will increase our basic understanding of mPFC-OFC interactions, and the role of this network in regulating fear learning and expression.

PROJECT SUMMARY Altered connectivity between emotional (vmPFC/amyg) and cognitive (vlPFC/dACC/OFC) control areas are thought to underlie compulsive and persistent behaviors in OCD. Human brain imaging can be used to image circuits, but direct manipulation of circuits is needed to evaluate their role in behavior. Because amyg/vmPFC and striatal circuitry is largely conserved in rodents, the overall goal of P5 is to use anatomical and optogenetic methods to test the hypothesis that connections between emotional and cognitive areas regulate persistent avoidance responses. We hypothesize that inputs to the cingulate and prelimbic corticies (Cg/PL, a putative dACC homologue) drive appropriate decisions to avoid (or not avoid) a stimulus previously associated with danger. In Aim 1, we will identify connection nodes within Cg/PL based on sites of convergence of inputs from amyg, medial orbital cortex (MO, putative OFC homologue), and lateral orbital cortex (LO, putative vlPFC homologue). In Aim 2, we will use cFos to characterize the activity of these Cg/PL nodes in a conditioned avoidance task, in which rats learn to step onto a nearby platform to avoid a tone-signaled footshock. We hypothesize that persistent avoidance resulting from failed extinction of avoidance is due to excessive activity in the Cg/PL emotional node (inputs from MO, amyg), whereas persistent avoidance resulting from failed devaluation of avoidance is due to deficient activity in the Cg/PL decision node (inputs from LO, amyg). In Aim 3, we will use an optogenetic approach to activate or silence, respectively, inputs from LO or MO to these Cg/PL nodes, to reverse persistent avoidance. The manipulation of these nodes in our avoidance task allows for a direct test of the connectivity hypotheses in P1 and P2, and silencing of specific inputs will help target rTMS placements for treatment of OCD (P4).

INVESTIGATOR DEVELOPMENT CORE Summary/ Abstract The Center for Collaborative Research in Minority Health and Health Disparities (CCRMHD) at the University of Puerto Rico Medical Sciences Campus proposes an Investigator Development Core (IDC) for its budgetary cycle 2017-2022. The CCRMHD will coordinate a pilot-project program (PPP) to nurture the growth of promising junior faculty within the UPR-MSC by soliciting, reviewing, and awarding funds to innovative proposals that will lead to competitive independent funding. The overall goals of the IDC are three-fold: 1) to mentor early career investigators as they transition to independent funding; 2) to fund innovative basic, behavioral and/or clinical pilot projects focusing on health disparities and/or minority health; 3) to match RCMI faculty with outside collaborators/mentors in order to strengthen collaborative networks. At the end of the proposed cycle, it is expected that 6-8 Early Stage Investigators (ESI), working on basic biomedical, behavioral and/or health services/clinical research, will have been funded, mentored, and well on their way to independent funding relevant to minority health and health disparities. We plan to accomplish this goal through the following Specific Aims: Grantees will receive a two-year grant of $35-50,000 per year in order to sustain studies for a sufficient period of time to compete successfully for outside funding. Mentoring activities will include informal meetings, rehearsal of scientific presentations, discussion of topics relevant to successful transition to running their own labs (using the best-seller book: At the Helm: Leading your Laboratory); and mock study-sections. Tracking and evaluation mechanisms will be established to measure scientific progress and ensure that the goals of the program are met, including increasing the number of publications, generating preliminary data, and increasing grant applications and awards (including R-type and K awards). Outcome metrics will be used to refine or refocus the solicitation, review, selection, and funding of applications made to the PPP. Staff from the Administrative Core will support and monitor full compliance with local and federal regulatory requirements. The IDC will be directed by Dr. Gregory J. Quirk, a senior neuroscientist at UPR-RCM, who currently serves as chair of a standing study-section at NIH-Center for Scientific Review and has been awarded an R35 grant at NIMH. Dr. Quirk, a basic biomedical researcher, will be assisted by an advisory committee that will include representation of the behavioral and health services/clinical areas. The IDC will coordinate closely with the Pilot Project Program of the Puerto Rico Clinical and Translational Research Consortium (PRCTRC), to share mentoring activities and resources and avoid support overlap.