FIGURE 9.

(A,B) Under- and over-modulation of emotion and arousal in trauma-related conditions. Image adapted with permission from Nicholson et al. (2017). An individual who encounters a traumatic situation is flooded with negatively valenced sensory stimuli, resulting in hyperactivation of the brainstem and midbrain PAG. An individual who develops a post-traumatic condition experiences persistent over-or under-modulated activity of the PAG and amygdala, resulting in hyper- and hypo- sensory-affective responsivity, respectively, at the level of the PAG. (A) Under-modulation or bottom-up predominance (solid arrows) results in hyperarousal and weak top-down neocortical modulation (dashed arrows) of sensory input and emotions. Situations incorporating sensory or emotional stimuli similar to the traumatic event, often over-generalized with regard to valence (i.e., every sensation of butterflies in the stomach is labeled as a sign of danger) triggers hyperarousal and a fight/flight response. (B) Over-modulation of lower brainstem and midbrain arousal and alarm centers (amygdala, PAG) is driven by frontal neocortical regions including the mPFC. An individual who experiences chronic, repeated traumatization, such as an adolescent who has grown up in a household with domestic violence and physical abuse, adapts to persistent threat through top-down blunting and avoidance. The adolescent is emotionally numb, withdrawn from relationships, and dissociative due to a scarcity of bottom-up sensory integrative influence and processing. Subcortical regions are prevented from nourishing the cortex with either negative or positive raw affective feelings or sensations unless they are extreme. am, amygdala; mPFC, medial prefrontal cortex; PAG: periaqueductal gray.