Amygdala-Prefrontal in Fear Extinction

Causal Dynamics of Human Amygdala-Prefrontal Circuits During Fear Extinction Learning

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 ability to reduce fear responses through extinction when threats are no longer present is essential for mental health. Deficits in extinction underlie fear-related disorders such as post-traumatic stress disorder (PTSD). A critical gap remains in understanding the neural mechanisms underlying fear extinction, which poses a major barrier to developing more effective therapeutic interventions. The amygdala (AMY)-prefrontal circuits are critical in fear extinction. In animal models, the lateral nucleus of the amygdala (LA) receives sensory inputs and initiates fear learning, while the basal nucleus of the amygdala (BA) integrates regulatory inputs from the ventromedial prefrontal cortex (vmPFC) and dorsal anterior cingulate cortex (dACC) for appropriate fear response. However, due to species-specific differences between animal and human neurobiology, the nucleus-specific contributions of the amygdala and their interactions with the vmPFC and dACC in human fear extinction and regulation remain poorly understood. Clinically indicated stereoelectroencephalography (SEEG) electrodes, which allow direct recording and stimulation of amygdala-prefrontal circuits, provide a unique opportunity to address this gap. The objective of this study is to determine the causal dynamics of amygdala-prefrontal circuits involved in fear extinction learning in participants with epilepsy undergoing SEEG monitoring. The study will address three aims: (1) Determine the intrinsic and stimulation-induced dynamics of human amygdala-prefrontal circuits. The study will characterize cause pathways and circuit-level interactions in amygdala-vmPFC-dACC circuits using intracranial recordings and electrical stimulation. (2) Characterize nucleus-specific and hemispherical lateralized dynamics of amygdala-prefrontal circuits during fear extinction. The study will examine the neural dynamics of the LA, BA, and left and right amygdala-prefrontal circuits during fear extinction and regulation. (3) Determine the effects of theta-burst stimulation of amygdala nuclei on fear extinction. Theta-burst stimulation will be applied to the LA and BA during extinction learning to examine how targeted stimulation modulates fear-related neural circuits and behavior.

Inclusion Criteria:

1. At least 18 years of age.
2. Able to understand the nature of the task.
3. Able to provide informed consent themselves or provide consent through their legally authorized representative.
4. Undergoing clinically indicated intracranial electrode implantation with coverage of at least one fear-related brain region, including the amygdala, hippocampus, cingulate cortex, insula, or prefrontal cortex.

Exclusion Criteria:

1. Under the age of 18.
2. Unable to understand the nature of the task.
3. Unable to provide informed consent themselves or provide consent through their legally authorized representative.
4. No clinically indicated intracranial electrode coverage in any fear-related brain region, including the amygdala, hippocampus, cingulate cortex, insula, or prefrontal cortex