Hemispheric Lateralization in PTSD

Both Rauch et al. (1996) and Teicher and his group (2002) found marked hemispheric lateralization in PTSD subjects who were exposed either to a negative memory or to a personalized trauma script. This suggests that there is differential hemispheric involvement in the processing of traumatic memories. The right hemisphere, which developmentally comes "on-line' earlier than the left hemisphere (Schore, 1994), is involved in the expression and comprehension of global nonverbal emotional communication (tone of voice, facial expression, visual/spatial communication), and allows for a dynamic and holistic integration across sensory modalities (Davidson, 1989). This hemisphere is particularly integrated with the amygdala, which assigns emotional significance to incoming stimuli and helps regulate the autonomic and hormonal responses to that information. While the right hemisphere is specialized in detecting emotional nuances, it has only a rudimentary capacity to communicate analytically, to employ syntax, or to reason (Schore, 2003).

In contrast, the left hemisphere, which mediates verbal communication and organizes problem-solving tasks into a well-ordered set of operations and process information in a sequential fashion (Davidson, 1998), seems to be less active in PTSD. It is in the area of categorization and labeling of internal states that people with PTSD seem to have particular problems (van der Kolk and McFarlane, 1996). The failure of left-hemisphere function during states of extreme arousal may contribute to the dere-alization and depersonalization reported in acute PTSD (Marmar et al., 1999; Shalev et al., 1996).

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