In animals, decreased hippocampal functioning has been shown to cause behavioral disinhibition98 and makes animals more likely to define incoming stimuli in the direction of emergency (fight/flight) responses. If the same is true for humans, this might contribute to the problems of PTSD patients with “taking in” and processing arousing information, and
to learn from such experiences. The decreased size of the hippocampus might play a role in the ongoing dissociation and misinterpretation of information in the direction of threat. Their altered Inhibitors,research,lifescience,medical biology would make them vulnerable to react to newly arousing stimuli as a threat, and to react with aggression, or withdrawal, depending on their premorbid personality.99 Symptom provocation studies Rauch, van der Kolk, and colleagues85 conducted a PET’ scan study of patients with PTSD in which they were exposed to vivid, detailed narratives of their own traumatic experiences. During exposure to the script of their traumatic experiences these subjects demonstrated heightened Inhibitors,research,lifescience,medical activity only in the right hemisphere, specifically, in the areas that are most involved in emotional arousal – the amygdala, insula, and the medial temporal lobe. During exposure to their traumatic scripts there was a significant decrease in activation of the left inferior frontal area – Broca’s
area – which is thought to be responsible for Inhibitors,research,lifescience,medical translating personal experiences Inhibitors,research,lifescience,medical into communicable language. Shin et al’s study,91 utilizing a slightly different paradigm, essentially confirmed these findings in a different trauma population. In another study, Lanius et al (submitted) exposed 6 subjects with PTSD and 6 controls to a traumatic script and measured their responses with functional magnetic resonance imaging (fMRT) scans, and consistently found decreased activation of the thalamus and of the dorsolateral prefrontal cortex in PTSD patients Inhibitors,research,lifescience,medical during exposure to their trauma scripts. These early neuroimaging studies of patients with PTSD present us with a range of surprising findings that force
us to reevaluate our previous concepts of the pathophysiology of PTSD. Of the various findings, increased activation of the amygdala in see more response to traumatic scripts is the least surprising. After all, it has been well established that the amygdala is centrally involved in the interpretation of the emotional valence Dipeptidyl peptidase of the incoming information and that confrontation with feared stimuli activates the amygdala and related structures.100 Exposure to traumatic scripts frequently provokes autonomic activation of patients with PTSD (eg, refs 48 and 101), and this is likely mediated by activation of the amygdala and related structures. It is well understood that the information evaluated by the amygdala is passed on to areas in the brainstem that control autonomic and neurohormonal response systems.
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