A recent twin study suggests that, unlike the hippocampus, volume loss in the ACC is secondary to the development of PTSD rather than a pre-existing risk factor.65 Functional imaging studies have found decreased activation of the medial PFC in PTSD patients in response to stimuli, such as trauma scripts,66,67 combat pictures and sounds,68 trauma-unrelated negative narratives,69 Inhibitors,research,lifescience,medical fearful faces,70 emotional stroop,71 and others, though there are also

discordant findings.41 Reduced activation of the medial PFC was associated with PTSD symptom severity in several studies and successful SSRI treatment has been shown to restore medial prefrontal cortical activation patterns.41 Of note, in the abovementioned conditioning experiment,57 extinction of conditioned fear was associated with decreased activation of the ACC, providing a biological correlate for imprinted traumatic memories in PTSD. Not surprisingly, given the connectivity between the amygdala and medial PFC, interactions in activation

Inhibitors,research,lifescience,medical patterns between these regions have been reported in PTSD, though the direction of the relationship is inconsistent across Inhibitors,research,lifescience,medical studies.41 The origin of neurobiological abnormalities in PTSD A number of studies have investigated the fundamental question as to whether the neurobiological changes identified in patients with PTSD represent markers of neural risk to develop PTSD upon exposure to extreme stress as opposed Inhibitors,research,lifescience,medical to abnormalities acquired through traumatic exposure or, most likely, a combination of both. As an example, low Cortisol levels at the time of a trauma predict subsequent development of PTSD. Thus, low levels of Cortisol might be a pre-existing risk factor that engenders the development of PTSD; low levels of Cortisol could disinhibit Inhibitors,research,lifescience,medical CRH/NE circuits and thereby GSK690693 research buy promote unopposed autonomic and neuroendocrine responses to stress, as well as augmented fear

conditioning and traumatic memory consolidation. Similarly, the reduced size of the hippocampus in PTSD has remained an unresolved question for many years. There has been considerable debate as to whether this brain region shrinks as a result of trauma exposure, or whether the hippocampus of PTSD patients might be smaller prior to trauma exposure. Studies in twins discordant for trauma exposure have and provided a means to address this question, though without complete resolution. Gilbertson and colleagues72 studied 40 pairs of identical twins, including Vietnam Veterans who were exposed to combat trauma and their twins who did not serve in Vietnam, and measured hippocampal volumes in all subjects. As expected, among Vietnam Veterans, the hippocampus was smaller in those diagnosed with PTSD as compared with those without a diagnosis. However, this brain region was abnormally smaller in non-PTSD twins as well, despite the absence of trauma exposure and diagnosis.