Page 24 - PIECES OF THE PUZZLE Eline Vissia

CHAPTER 1
function of dissociation (Spiegel, Cardena 1991, Van der Kolk, Fisler 1995, Van der Hart et al. 2004).
Stress has effects on brain areas that play a critical role in learning and memory, including the hippocampus and prefrontal cortex (PFC) (Bremner et al. 2004, McEwen, Nasca & Gray 2015). It has been well documented that stress hormones may damage the brain when secretion is excessive or unnecessarily prolonged (McEwen 2002). The hippocampus, in particular, is a major target for stress hormones due to the abundant presence of receptors for glucocorticoids. Early-life chronic exposure to stress and glucocorticoids could result in the suppression of neurogenesis, a reduction in dendritic branching or neuronal atrophy or neural loss in the hippocampus (McEwen 1999, Sapolsky 1993), which is involved in memory processes. Childhood maltreatment is considered to be a severe life stressor and specific effects of maltreatment may depend on the age at the time of the maltreatment, and severity, frequency and duration of the maltreatment and the identity of the abuser (Andersen et al. 2008). Studies examining the neuroanatomical correlates of childhood maltreatment in adults found decreased gray matter volume in the hippocampus (Vythilingam et al. 2002, Kitayama et al. 2005) and changes in the PFC (Teicher et al. 2003, Van Harmelen et al. 2010).
Brain structure
Structural magnetic resonance imaging (sMRI) studies found in general a smaller volume of the hippocampus in PTSD patients and childhood- maltreated individuals as compared with traumatized and healthy controls (Karl et al. 2006, Kuhn, Gallinat 2013). For DID, some studies reported smaller volume of the hippocampus (Ehling, Nijenhuis & Krikke 2008, Irle et al. 2009, Tsai et al. 1999, Vermetten et al. 2006) as compared with healthy controls. As hippocampal volume loss has been linked to elevated levels of glucocorticoids secretion during stress, these results suggest a trauma- related nature of DID (McEwen 1999, Sapolsky 1993). To date, no studies have compared hippocampus morphology in DID with a trauma-related disorder such as PTSD to test for similarities of these disorders. In order to directly test the trauma model’s hypothesis, we will include both PTSD and healthy controls as control groups for DID and compare hippocampus shape and volume. As the prefrontal cortex matures, response to stress becomes more restrictive (Lyss et al. 1999) due to the inhibitory influence of the prefrontal
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