Identity state-dependent processing of neutral and traumatic scripts in Dissociative Identity Disorder as assessed by PET (Positron Emission Tomography)
Introduction:Patients with dissociative identity disorder (DID) have two or more distinctive identities with their own pattern of perception, reaction and thinking. This disorder was formerly known as Multiple Perrsonality Disorder (MPD). This can be a consequence of childhood trauma resulting in "traumatic" identities with their own particular reaction to recollection of, or emotional responses to, the traumatic memories. Furthermore "neutral" identities exist with no, or in any case less, recollection of these memories. DID is described in many case studies, but almost no quantitative psychofysiological multisubject studies have been reported.
PET investigation is performed because dissociative disorders are unsatisfactorily understood. This hinders the diagnostic and treatment of patients with DI
Aim:Study brainactivity in DID patients, listening to autobiographic texts in different identity states, to objectivate identity dependent information processing in this psychiatric disorder.
Hypothesis:Traumatic identity listening to neutral text or in neutral state shows different or no brain activation as compared to traumatic identity listening to traumatic text.
Methods:Seven women, meeting DSM-IV criteria for DID, were, in two different identities, exposed to two auditory autobiographical texts while undergoing 3D PET imaging. Regional cerebral bloodflow (rCBF) measured with the Siemens EXACT HR+ after intraveneus injection of H215O (500 MBq), obtaining 120-sec scans. Four different conditions were obtained twice, resulting in eight scans. The complete scanning sequence was Nn, Nt, Tn, Tt, Tn, Tt, Nn and Nt. The first character indicating the personality state neutral or Traumatic) and the second character the content of the text (neutral or traumatic). Data was analysed with statistical parametric mapping using SPM96 (multisubject different conditions with replications), after realignment and spatial normalisation
Results:Different brain activation was found in the two identity states while listening to the traumatic text. In the Traumatic identity rCBF in the left temporal area differed significantly between the two texts. The Traumatic state exposed to traumatic text showed different brain activation patterns compared to neutral text or in Neutral state.
Conclusion/Discussion:Traumatic identity state exposed to traumatic text showed different or no brain activation compared with neutral text or in Neutral state. Brain activation in patients with DID is state dependent. The temporal lobe may be a mediating factor in the psycho-physiology of patients with DID. Identity state dependent information processing is shown in an objective way. Differential dissociation, thus state dependent brain (re-)activity was found. These findings contribute to the scientific objectivity on the subjective experience of patients with DID.