64 The hippocampus and portions of the prefrontal cortex, which n

64 The hippocampus and portions of the prefrontal cortex, which normally modulate amygdala activity, are also dysregulated in individuals with PTSD.65 The implication of hippocampal dysfunction may be of particular relevance here. As noted above, the dorsal hippocampus is critical for contextual conditioning—the association of a fear response

with the particular context in which training occurred.61 The faithful encoding and recall of the training-associated context is likely to be critical to prevent promiscuous generalization of the fear response to other, innocuous contexts. Reduced recruitment or dysfunction of the hippocampus—such as may occur after intense or chronic stress31—may Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical lead to reduced efficacy of contextual encoding, and thus set the stage for untoward contextual generalization. This association of normal fear learning mechanisms with the pathophysiology of PTSD holds promise for the

development of new therapeutic strategies.56 Core cognitive-behavioral therapy (CBT) techniques for the treatment Inhibitors,research,lifescience,medical of PTSD rely on extinction learning: the repeated pairing of fear-associated stimuli or contexts with innocuous outcomes, leading over time to a new set of associations that, it is hoped, will occlude the fear-associated pairings. Extinction is an active form of learning that depends on the NMDA Luminespib molecular weight receptor and a suite of downstream plasticity-associated pathways. Pharmacological enhancement of NMDA signaling during extinction training using D-cycloserine has been shown to accelerate extinction-based CBT in several anxiety disorders Inhibitors,research,lifescience,medical (eg, ref 66,67). A recent trial suggests that this approach may be useful in PTSD.68 Interference with the mechanisms of trauma-associated learning may be possible in the window hours or days after a traumatic event, during

Inhibitors,research,lifescience,medical the process of consolidation—the collection of molecular, cellular, and systems-level processes whereby memories are converted from a labile state to a more robust, long-lasting form. Interference with a number of different molecular mechanisms associated with consolidation has been shown to disrupt long-term fear learning in animals.58 In humans, the logistical challenges of delivering a pharmacological intervention after a trauma, which is inherently an unpredictable and disruptive event, have limited all rigorous studies of this strategy towards secondary prevention of the development of PTSD; however, this remains an exciting potential area of therapeutic development.56 Substantial interest has focused, in recent years, on the phenomenon of reconsolidation in the context of fear memories. The importance of reconsolidation was not widely appreciated until about a decade ago.69 The key insight underlying this phenomenon is that under certain circumstances, the recall of a memory transiently puts it into a labile state.

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