Fear Extinction

Anxiety disorders remain are among the most prevalent psychiatric conditions and are associated with negative outcomes spanning poor health to increased suicide risk. While exposure therapy is recognized as a gold standard empirically supported treatment, many individuals fail to achieve adequate response. Exposure therapy is grounded in fear extinction learning models, which suggest that anxiety diminishes when individuals repeatedly confront their fears. To improve exposure-based interventions, it is critical to enhance our understanding of underlying mechanisms of fear extinction and how to better target these mechanisms. Fear extinction requires basic neurocognitive abilities that allow individuals to learn from and adapt to experiences confronting feared situations. Emerging cross sectional and experimental data suggest that working memory is a particularly important neurocognitive process that is associated with fear learning outcomes. By enhancing working memory through experimental manipulations like cognitive training, we may improve the fear extinction learning processes essential for successful exposure therapy. Unlike other neurocognitive enhancements (e.g., medications), computer-based working memory training offers high mechanistic precision, ease of administration, and low cost. The long-term goal of this research is to develop a novel mechanistic understanding of the neurocognitive processes involved in exposure-based fear extinction learning, ultimately aiming to improve interventions for anxiety disorders. This study will test the effects of manipulating working memory prior to a massed exposure paradigm, comparing working memory training plus massed exposure (WMT+Ex) to a sham training plus massed exposure (ST+Ex) condition. Using public speaking anxiety as a clinical exemplar, we will employ a rigorous experimental trial design combined with a validated single-visit speech exposure paradigm to assess fear extinction learning outcomes through multiple measures, including behavioral, physiological, neural, and self-report. The central hypothesis is that WMT+Ex will improve markers of fear extinction learning considered to underlie clinical response in exposure therapy. Specific aims are to 1) determine the extent to which working memory training delivered prior to massed exposure improves behavioral and neural markers of fear extinction learning, and 2) evaluate the effects of working memory training delivered prior to massed exposure on fear extinction learning occurring during exposure. This study is expected to achieve two goals: first, to advance our understanding of the neurocognitive mechanisms of fear extinction through a rigorous experimental design, and second, to validate a combined working memory training and exposure paradigm. If successful in enhancing fear extinction, this approach could be further explored in therapeutic formats to assess its clinical effects.

The goal of this clinical trial is to understand how brain circuits involving the amygdala and prefrontal cortex contribute to fear learning and extinction. Fear extinction is the process by which a fear response decreases when a threat is no longer present. The study will include participants with epilepsy who are undergoing stereoelectroencephalography (SEEG) monitoring as part of their clinical care. The main questions this study aims to answer are: How do the amygdala and prefrontal cortex interact during fear learning and extinction? Do different parts and hemispheres of the amygdala have different roles in fear learning and extinction? How does electrical stimulation of the amygdala affect these brain circuits and fear extinction? Participants will complete tasks involving fear learning and extinction while researchers record brain activity from clinically implanted electrodes. Researchers will also use electrical stimulation via these electrodes to study how amygdala activity affects other brain regions and fear extinction.

The goal of the current project is to establish the efficacy and mechanisms of exercise-enhanced fear extinction retrieval and generalization in posttraumatic stress disorder (PTSD). Exposure therapy is the gold standard treatment for PTSD, yet is only associated with remission rates of \~55% and in clear need of improvement. Exposure therapy is hypothesized to work through mechanisms of fear extinction learning, and as such, laboratory-based fear extinction paradigms are widely used as models of exposure therapy. Recent data demonstrates that moderate-intensity aerobic exercise, delivered specifically during or after fear extinction learning, can boost the consolidation of fear extinction learning. Consistent with emerging models of exercise's pro-extinction effect, our pilot data among women with PTSD found that moderate intensity aerobic exercise delivered after fear extinction learning leads to a reduction in subsequent fear responding 24hrs later, an effect that was mediated by exercise-induced increases in peripheral brain derived neurotrophic factor (BDNF). Our pilot data using multivariate pattern analyses (MVPA) also identified divided neurocircuitry organization of fear vs safety memories, and that this divided neural organization was altered in PTSD. Building on our pilot data, the current project would 1) compare the impact of different intensities of exercise delivered following fear extinction learning on multimodal measures of fear extinction retrieval and generalization, 2) identify the impact of exercise on MVPA representations of fear vs safety memories, and 3) demonstrate that spontaneous reactivations of extinction encodings in the acute consolidation window operate as candidate mechanisms by which exercise enhances extinction retrieval and generalization. Using a 3-day fear conditioning, fear extinction, and fear extinction retrieval and recognition task during functional magnetic resonance imaging (fMRI), 200 adults with PTSD would be randomly assigned to either resting control or 30min of either light, moderate, or high intensity exercise. Testing dose-response relationships between exercise intensity and fear extinction will inform translation of this research to clinical settings. A one week-follow-up extinction retrieval test would investigate the impact of exercise on longer-term retention. This project would provide a critical evaluation of the impact of aerobic exercise on consolidation and recall of extinction learning in PTSD samples, thereby providing a strong foundation to translate this research to clinical care and enhance clinical outcomes for PTSD. The project would also provide general knowledge regarding dose-response relationships and neural mechanisms that support enhanced extinction, thereby informing development of additional novel treatments.