Science
We use cutting-edge techniques — chemogenetics, electrophysiology, and calcium imaging in awake, behaving animals — to map the brain circuits underlying fear, memory, and relapse.
Contextual Control of Extinction
Extinction-based therapies, such as prolonged exposure, are used to reduce fear in patients with fear and anxiety disorders. Unfortunately, the loss of fear that occurs during extinction is often limited to the extinction context and vulnerable to relapse. We are mapping the neural circuits involved in extinction memory and fear relapse, focusing on connections between the hippocampus, amygdala, and prefrontal cortex. A recent focus has been the role of the nucleus reuniens, which interconnects the hippocampus and medial prefrontal cortex, in extinction acquisition and retrieval.
Recent paper: Tuna, Mourão & Maren (2026). Theta-paced stimulation of the thalamic nucleus reuniens entrains mPFC–HPC oscillations and facilitates the acquisition of extinction memories. Brain Stimulation, 19(1):102984. PubMed ↗
NIH R01MH065961
Stress and Extinction Learning
Patients with post-traumatic stress disorder (PTSD) are resistant to extinction. This undermines therapy, because it makes PTSD patients vulnerable to relapse. We have discovered that extinction learning is impaired when it occurs soon after trauma, resulting in an “immediate extinction deficit.” We have found that locus coeruleus norepinephrine (LC-NE) released in the amygdala suppresses prefrontal cortical circuits involved in extinction learning.
Recent paper: Bayer et al. (2026). Locus coeruleus–amygdala circuit disrupts prefrontal control to impair fear extinction. Proc. Natl. Acad. Sci. USA, 123(11):e2528250123. PubMed ↗
NIH R01MH117852
Manipulating Fear and Extinction Engrams
Extinction does not erase fear memories, and this leads to relapse. What if traumatic memories could be erased? We are using activity-dependent viral approaches to capture the neuronal ensembles representing fear memories, with the hope of manipulating — even erasing — those memories. To this end, we have developed a behavioral procedure to covertly retrieve hippocampal-dependent context memories.
Recent paper: Hassell et al. (2025). Hippocampal ensembles regulate circuit-induced relapse of extinguished fear. Molecular Psychiatry, 30(10):4700–4709. PubMed ↗
NIH MH065961