The innate alarm system (IAS), comprised of functionally connected brain regions including the brainstem, amygdala, pulvinar, and frontotemporal cortex, is a fast subcortical brain network facilitating rapid responses to threat. Post-traumatic stress disorder (PTSD) features subconscious and conscious threat detection, together contributing to hyperarousal symptoms. Emerging literature identifies aberrant threat-related neurocircuitry involved in subconscious and conscious threat processing in PTSD. We review this literature, focusing on subconscious threat processing and its relation to the IAS. Available evidence indicates increased neural activity and functional connectivity between IAS brain regions (e.g. locus coeruleus, superior colliculus, amygdala, and prefrontal cortex). These alterations are observed during both subconscious threat processing and at rest, suggesting increased defensive posturing, maintained in the absence of overt threat.
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