title: Neurophysiological correlates of dissociative symptoms.
abstract: OBJECTIVE
  Dissociation is a mental process with psychological and somatoform manifestations, which is closely related to hypnotic suggestibility and essentially shows the ability to obtain distance from reality. An increased tendency to dissociate is a frequently reported characteristic of patients with functional neurological symptoms and syndromes (FNSS), which account for a substantial part of all neurological admissions. This review aims to investigate what heart rate variability (HRV), EEG and neuroimaging data (MRI) reveal about the nature of dissociation and related conditions.
  
  
  METHODS
  Studies reporting HRV, EEG and neuroimaging data related to hypnosis, dissociation and FNSS were identified by searching the electronic databases Pubmed and ScienceDirect.
  
  
  RESULTS
  The majority of the identified studies concerned the physiological characteristics of hypnosis; relatively few investigations on dissociation related FNSS were identified. General findings were increased parasympathetic functioning during hypnosis (as measured by HRV), and lower HRV in patients with FNSS. The large variety of EEG and functional MRI investigations with diverse results challenges definite conclusions, but evidence suggests that subcortical as well as (pre)frontal regions serve emotion regulation in dissociative conditions. Functional connectivity analyses suggest the presence of altered brain networks in patients with FNSS, in which limbic areas have an increased influence on motor preparatory regions.
  
  
  CONCLUSIONS
  HRV, EEG and (functional) MRI are sensitive methods to detect physiological changes related to dissociation and dissociative disorders such as FNSS, and can possibly provide more information about their aetiology. The use of such measures could eventually provide biomarkers for earlier identification of patients at risk and appropriate treatment of dissociative conditions.
authors.affiliation: Epilepsy Centre Kempenhaeghe, , Heeze, The Netherlands.
authors.forename: Sylvie J M
authors.initials: SJ
authors.lastname: van der Kruijs
authors.forename: Nynke M G
authors.initials: NM
authors.lastname: Bodde
authors.forename: Evelien
authors.initials: E
authors.lastname: Carrette
authors.forename: Richard H C
authors.initials: RH
authors.lastname: Lazeron
authors.forename: Kristl E J
authors.initials: KE
authors.lastname: Vonck
authors.forename: Paul A J M
authors.initials: PA
authors.lastname: Boon
authors.forename: Geert R
authors.initials: GR
authors.lastname: Langereis
authors.forename: Pierre J M
authors.initials: PJ
authors.lastname: Cluitmans
authors.forename: Loe M G
authors.initials: LM
authors.lastname: Feijs
authors.forename: Paul A M
authors.initials: PA
authors.lastname: Hofman
authors.forename: Walter H
authors.initials: WH
authors.lastname: Backes
authors.forename: Jacobus F A
authors.initials: JF
authors.lastname: Jansen
authors.forename: A P
authors.initials: AP
authors.lastname: Aldenkamp
mesh_terms: D001921:Brain / Q000502:physiology / Q000503:physiopathology*; D058256:Brain Waves / Q000502:physiology*; D004213:Dissociative Disorders / Q000150:complications / Q000503:physiopathology*; D059907:Functional Neuroimaging; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006990:Hypnosis; D009422:Nervous System Diseases / Q000150:complications / Q000503:physiopathology* / Q000523:psychology