The Neuroscience of Dissociation

Neuroimaging and psychophysiology have begun to map what happens in the brain during dissociative states — revealing a consistent pattern of altered integration between brain regions.

• The prefrontal cortex (PFC) — responsible for narrative integration, emotional regulation, and sense of agency — shows reduced activity or connectivity during dissociative episodes

• The amygdala, which encodes emotional salience, is dysregulated: in hyperarousal (flashback), it overactivates; in hypoarousal (numbing/dissociation), inhibitory circuits from the PFC and anterior cingulate suppress it — sometimes excessively

• Memory: traumatic memories are often encoded through the hippocampus-amygdala circuit differently from ordinary autobiographical memory — fragmented, sensory-dominant, poorly contextualized in time

• The Polyvagal framework (Porges) identifies a dorsal vagal shutdown state — physiological collapse — as the neurobiological underpinning of freeze-based dissociation

• Cortisol and the HPA axis: chronic stress dysregulates cortisol release, which in turn disrupts hippocampal consolidation of memory — a mechanism linking chronic trauma exposure to dissociative amnesia

Key research: Lanius et al. (2010) identified two subtypes of PTSD response — a hyperarousal subtype and a dissociative subtype — with opposite neurobiological signatures on fMRI, explaining why some trauma survivors relive while others go numb.