Mako Shimizu | 2026 I.S. Symposium
Name: Mako Shimizu
Title: Fear Engrams are Formed in the Locus Coeruleus during Contextual Fear Conditioning
Major: Neuroscience
Pathway: Public Health
Advisor: Amy Jo Stavnezer
Contextual fear memory is a vital survival mechanism that allows organisms to recognize and respond to environments associated with danger. Fear memory is closely linked to post-traumatic stress disorder (PTSD), a psychological condition triggered by traumatic experiences that result in persistent symptoms, such as flashbacks and hypervigilance. Traditional research on fear memory has focused on the hippocampus and amygdala, brain regions responsible for learning and emotional processing, respectively. However, recent studies have drawn attention to the Locus Coeruleus (LC), a brainstem nucleus known for regulating arousal and stress responses. The LC modulates hippocampal and amygdala activation and is an intermediate pathway between the brain and the vagus nerve, indicating a direct connection to the autonomic nervous system. My independent study investigated whether the LC directly participates in contextual fear memory storage through the formation of engrams, neuronal populations that encode and retain specific memories in a mouse model. Using contextual fear conditioning and immunohistochemistry, we found that fear engrams are formed in the LC to store fear memories directly, rather than merely modifying them by modulating other brain regions. Our finding suggests the existence of extinction engrams in the LC, that may be suppressing the reactivation of original fear engrams. The present study opens new potential strategies for treating PTSD, including neuromodulatory interventions targeting the LC with vagus nerve stimulation to actively 鈥渞eshape鈥 memory-storing networks with current exposure therapy, engram-circuit-specific neuromodulation, and pharmacological approaches to LC engrams.
Posted in Symposium 2026 on May 1, 2026.
