Maltreatment Exposure, Brain Structure, and Fear Conditioning in Children and Adolescents.

Alterations in learning processes and the neural circuitry that supports fear conditioning and extinction represent mechanisms through which trauma exposure might influence risk for psychopathology. Few studies examine how trauma or neural structure relates to fear conditioning in children. Children (n=94) aged 6-18 years, 40.4% (n=38) with exposure to maltreatment (physical abuse, sexual abuse, or domestic violence), completed a fear conditioning paradigm utilizing blue and yellow bells as conditioned stimuli (CS+/CS-) and an aversive alarm noise as the unconditioned stimulus. Skin conductance responses (SCR) and self-reported fear were acquired. Magnetic resonance imaging data were acquired from 60 children. Children without maltreatment exposure exhibited strong differential conditioning to the CS+ vs CS-, based on SCR and self-reported fear. In contrast, maltreated children exhibited blunted SCR to the CS+ and failed to exhibit differential SCR to the CS+ vs CS- during early conditioning. Amygdala and hippocampal volume were reduced among children with maltreatment exposure and were negatively associated with SCR to the CS+ during early conditioning in the total sample, although these associations were negative only among non-maltreated children and were positive among maltreated children. The association of maltreatment with externalizing psychopathology was mediated by this perturbed pattern of fear conditioning. Child maltreatment is associated with failure to discriminate between threat and safety cues during fear conditioning in children. Poor threat-safety discrimination might reflect either enhanced fear generalization or a deficit in associative learning, which may in turn represent a central mechanism underlying the development of maltreatment-related externalizing psychopathology in children.

Amygdala response to negative stimuli predicts PTSD symptom onset following a terrorist attack.

OBJECTIVE: Individuals with posttraumatic stress disorder (PTSD) exhibit heightened amygdala reactivity and atypical activation patterns in the medial prefrontal cortex (mPFC) in response to negative emotional information. It is unknown whether these aspects of neural function are risk factors for PTSD or consequences of either trauma exposure or onset of the disorder. We had a unique opportunity to investigate this issue following the terrorist attacks at the 2013 Boston Marathon and the ensuing manhunt and shelter in place order. We examined associations of neural function measured prior to the attack with PTSD symptom onset related to these events. METHODS: A sample of 15 adolescents (mean age = 16.5 years) who previously participated in a neuroimaging study completed a survey assessing posttraumatic symptoms related to the terrorist attack. We examined blood oxygen level dependent (BOLD) response to viewing and actively down-regulating emotional responses to negative stimuli in regions previously associated with PTSD, including the amygdala, hippocampus, and mPFC, as prospective predictors of posttraumatic symptom onset. RESULTS: Increased BOLD signal to negative emotional stimuli in the left amygdala was strongly associated with posttraumatic symptoms following the attack. Reduced bilateral hippocampal activation during effortful attempts to down-regulate emotional responses to negative stimuli was also associated with greater posttraumatic symptoms. Associations of amygdala reactivity with posttraumatic symptoms were robust to controls for pre-existing depression, anxiety, and PTSD symptoms and prior exposure to violence. CONCLUSIONS: Amygdala reactivity to negative emotional information might represent a neurobiological marker of vulnerability to traumatic stress and, potentially, a risk factor for PTSD.