Recovery from Posttraumatic Stress Requires Dynamic and Sequential Shifts in Amygdalar Connectivities

Abstract

The neural mechanisms underlying the development and maintenance of posttraumatic stress disorder (PTSD) have long been studied. However, little is known about the neural correlates of the recovery process from PTSD. A 5-year longitudinal study was conducted to investigate the trajectory of structural connectivities of the amygdala in disaster survivors with PTSD. Thirty disaster survivors, who were diagnosed with PTSD, and 29 healthy individuals, who were not exposed to trauma, underwent three waves of assessments including neuroimaging scanning over a 5-year period from the time of the disaster at approximately 1.3-year intervals. All disaster survivors showed significant improvements in PTSD symptoms over time. Using diffusion tensor imaging analysis, a 5-year trajectory of amygdalar structural connectivities with key brain regions was assessed. The amygdala-insula connection was initially strengthened and then normalized during recovery, while the amygdala-prefrontal cortex (PFC) connection was at first unaffected, then strengthened, and eventually normalized. The lower tract strength of the amygdala-thalamus connection normalized during recovery, while that of amygdala-hippocampus connection remained low. The greater amygdala-PFC connectivity was associated with less PTSD symptom severity. The present longitudinal study revealed that recovery from PTSD parallels dynamic and sequential shifts in amygdalar connectivities with multiple brain regions, suggesting the expanded view of fear circuitry including the insula and thalamus, beyond the traditional model which primarily involves the amygdala, PFC, and hippocampus.