Impaired Neural Pattern Separation During Implicit Emotion Regulation in PTSD: An MVPA fMRI Study.

Implicit emotion regulation (IER) operates automatically and supports adaptive social-affective functioning. Although PTSD involves marked IER disturbances, the large-scale functional connectivity architecture supporting implicit emotional processing remains unclear. The Shifted Attention Emotion Appraisal Task (SEAT) offers an ecologically relevant framework for probing these processes. One hundred twenty-three adults (PTSD: n = 78; trauma-exposed controls: n = 45) completed fMRI during SEAT. Whole-brain functional connectivity multivariate pattern analysis (fc-MVPA) identified data-driven, condition-specific connectivity patterns distinguishing groups. MVPA-derived clusters were further assessed using seed-based and ROI-to-ROI analyses. fc-MVPA revealed three frontal-anchored connectivity patterns spanning frontoparietal, salience, and executive networks. Seed-based analyses centered on the right frontal pole showed increased coupling with posterior default mode and visual regions and reduced connectivity with frontal control systems. Dysconnectivity varied across regulatory stages, including frontal-occipital hyperconnectivity during threat-related attention shifts and frontal-midline hypoconnectivity during neutral appraisal. Greater re-experiencing severity was nominally associated with reduced multivariate network strength during implicit processing and appraisal; however, these associations did not survive correction for multiple comparisons and should be considered exploratory. Implicit regulation deficits in PTSD reflect distributed network dysfunction rather than localized abnormalities. Disrupted coordination among control, perceptual, and self-referential systems may limit flexible emotional responses. Integrating SEAT with fc-MVPA identifies connectivity patterns relevant to maladaptive emotional processing and advances network-level models of dysregulation in PTSD.