Neural mechanisms underlying implicit emotion regulation deficit in relational and nonrelational trauma PTSD: Insights from the Nested Hierarchical Model of Self.

Posttraumatic stress disorder (PTSD) exhibits marked heterogeneity, with relational (R; interpersonal) and nonrelational (NR; environmental) trauma subtypes demonstrating distinct psychopathological trajectories. Despite clinical recognition of these differences, their neurobiological underpinnings of emotion processing remain poorly understood. Guided by the Nested Hierarchical Model of Self (NHMS) - which posits trauma-type-specific disruptions in hierarchical self-processing systems - this study investigated neural mechanisms differentiating among PTSD subtypes during implicit emotion regulation. A sample of 122 participants, including patients with PTSD (R: n = 51; NR: n = 29) and trauma-exposed controls matched by trauma type (R: n = 22; NR: n = 20), underwent functional magnetic resonance imaging while performing the Shifted Attention Emotion Appraisal Task. Behavioral assessments and trauma typology coding were complemented by regions of interest (ROI)-based and whole-brain analyses. Results revealed that PTSD-R showed hypoactivation in right superior frontal gyrus (during implicit emotion regulation; BA9; p = 0.049, ηp2 = 0.033), whereas PTSD-NR exhibited hyperactivation in fusiform (during emotion modulation by attention shifting; p = 0.036, ηp2 = 0.037). Symptom severity inversely correlated with social support (r = -0.353 to -0.417, p < 0.01), with relational PTSD reporting the lowest support (p < 0.001). Across conditions, dorsolateral prefrontal clusters (BA8/9) demonstrated anticorrelations with default-mode regions (r = -0.272 to -0.549, p < 0.01) aligning with NHMS' predictive coding framework. These findings validate trauma-type-specific neural hierarchies, suggesting relational trauma disrupts top-down self-identity schemas, while NR trauma amplifies bottom-up threat detection. The study advances precision psychiatry by linking implicit regulation biomarkers to targeted interventions - cognitive restructuring for PTSD-R and interoceptive recalibration for PTSD-NR.