Unraveling the Fear Circuit: A Novel Computational Model of Fear Acquisition, Extinction, and Subsequent Recovery

Poster Session B - Sunday, April 14, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Ms. Shreya Rajagopal¹ (shreyara@umich.edu), Dr. Thad Polk¹; ¹University of Michigan

Animals gradually lose fear responses they had previously acquired toward a stimulus. Such fear extinction is both context-specific and temporary – the fear returns immediately if the animal is placed in a new context (Renewal), or after a long delay within the extinction context itself (Spontaneous Recovery). Since exposure therapy in anxiety-based disorders relies primarily on fear extinction mechanisms, understanding these mechanisms is fundamental to ensuring long-term and context-general solutions for these disorders. Using recent findings about the fear circuit in animal brains as reference, we propose a novel computational model of fear acquisition, extinction, and subsequent return. The key features of our model include [1] Distinct pathways to process cue (sensory cortex to Basolateral Amygdala (BLA)) and context information (Hippocampus to Basolateral Amygdala (BLA)) [2] Cue and context inputs connecting to distinct BLA populations (negative and positive reward-responsive regions) [3] Competition between these BLA populations to determine the final fear response. [4] Connection weight updates based on the presence and valence of external reward and stored BLA responses to presented stimulus based on previous trials (memory engrams). [5] Distinct learning rates and thresholds for cue and context pathway weight updates. And [6] Decay of context-pathway connections. This model produces both Spontaneous Recovery and Renewal effects and also demonstrates differences between different kinds of extinction by changing extinction contexts or pairing the conditioned stimulus with a positive reward. The model also provides novel, testable hypotheses about how fear extinction is implemented in the brain.

Topic Area: EMOTION & SOCIAL: Emotional responding