Structural covariance, regional topology, and volumetric aspects of amygdala subnuclei in posttraumatic stress disorder using ultra-high field imaging.

The amygdala is a subcortical brain structure involved in threat processing and implicated in various psychopathology. Previous efforts to map amygdala subnuclei connectivity have been hindered by technological limitations. This study used ultra-high field imaging to investigate the covariance profiles of amygdala subnuclei to better understand their contribution to trauma-related psychopathology and posttraumatic stress disorder (PTSD). Participants included 59 non-trauma-exposed controls (NEC; 51% female), 78 trauma-exposed controls (TEC; 65% female), and 73 individuals with PTSD (93% female) who completed T1-weighted MP2RAGE anatomical scans using a 7-Tesla MRI scanner. FreeSurfer was used to parcellate 105 brain regions including nine bilateral amygdala subnuclei. Pearson's r correlations were computed for each subnuclei-brain region pair, corrected for age, sex, education, and total brain volume. Gray matter volumes, topological connectivity (nodal degree) using graph analysis, and subnuclei-brain region covariances were compared between-groups. There were between-group volumetric differences for the lateral nuclei (left: NEC < PTSD/TEC; right: PTSD < NEC/TEC), and higher nodal degree of the right paralaminar subnucleus for TEC (vs NEC). Covariance patterns differed between-groups, with lower PTSD (vs NEC) structural covariances for left cortical and central nuclei, and higher TEC (vs NEC) covariances for left lateral, basal, cortical, and anterior-amygdaloid-area, right cortico-amygdaloid transition, and bilateral paralaminar nuclei. This study is the first to reveal differences in amygdala subnuclei covariance profiles along the trauma-spectrum using ultra-high field imaging. Findings suggest that amygdala subnuclei could have differential connectivity profiles in trauma-related conditions and ultra-high field imaging studies are needed to more precisely understand their role.