In a series of studies we demonstrated that memories of trauma initially tend to have few autobiographical elements: When PTSD patients have their flashbacks, the trauma is relived as isolated sensory, emotional, and motoric imprints, without much of a storyline. We have shown this in victims of childhood abuse (van der Kolk and Fisler, 1995), assaults, and accidents in adulthood (van der Kolk et al., 1997) and in patients who gained awareness during surgical procedures (van der Kolk et al., 2000). These studies support the notion that traumatic memories result from a failure of the CNS to synthesize the sensations related to the event into an integrated semantic memory. While most patients with PTSD construct a narrative of their trauma over time, it is characteristic of PTSD that sensory elements of the trauma itself continue to intrude as flashbacks and nightmares, in states of consciousness where the trauma is relived, unintegrated with an overall sense of current time, place, and sense of self. Because traumatic memories are so fragmented, it seems reasonable to postulate that extreme emotional arousal leads to a failure of the CNS to synthesize the sensations related to the trauma into an integrated whole.
These observations suggest that in PTSD the brain's natural ability to integrate experience breaks down. A large variety of CNS structures have been implicated in such integrative processes: (1) the parietal lobes integrate information between different cortical association areas (Damasio, 1999), (2) the hippocampus creates a cognitive map that allows for the categorization of experience, connecting it with other autobiographical information (O'Keefe and Nadel, 1978), (3) the corpus callosum allows for the transfer of information by both hemispheres (Joseph, 1988), integrating emotional and cognitive aspects of the experience, (4) the cingulate gyrus, which is thought to play a role both as amplifier and filter, helps integrate the emotional and cognitive components of the mind (Devinsky et al., 1995), and (5) various prefrontal areas, where sensations and impulses are "held in mind" and compared with previous information to plan appropriate actions. Recent neuroimaging studies of patients with PTSD have suggested a role for all of these structures in the neurobiology of PTSD, though, at this point, many of the findings are quite variable and at times contradictory.
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