title: Separating depersonalisation and derealisation: the relevance of the "lesion method".
abstract: OBJECTIVE
  Depersonalisation (DP) and derealisation (DR) are often met with in patients with a wide range of localisable neurological conditions. This suggests that the "lesion method" might be a valid approach to study the neurobiology of DP/DR. However, the fact that anxiety can trigger DP/DR makes it difficult to establish whether the presence of DP/DR in neurological patients is mainly determined by coexisting anxiety or by lesion location. To overcome this difficulty, we suggest the study of neurological phenomena, which although not considered as DP/DR, bear enough phenomenological resemblance with them as to warrant their use as models.
  
  
  METHODS
  One patient with "visual hypoemotionality" and another with "hemiasomatognosia" are described in detail together with a selective literature review.
  
  
  RESULTS
  Complaints of patients with visual hypoemotionality are indistinguishable from those of patients with "visual derealisation". There is also a phenomenological overlap between "asomatognosia" and the symptom of "body alienation", which is a central feature of depersonalisation.
  
  
  CONCLUSIONS
  Phenomenological similarities between visual hypoemotionality and DR suggest that a disruption of the process by means of which perception becomes emotionally coloured may be an underlying mechanism in both conditions. Likewise, phenomenological overlaps with asomatognosia suggest that DP might result from parietal mechanisms disrupting the experience of body ownership and agency. These findings give validity to the notion that DP and DR may have distinct neurobiological mechanisms.
authors.affiliation: Depersonalisation Research Unit, Institute of Psychiatry, Division of Psychological Medicine, 103 Denmark Hill, London SE5 8AZ, UK. M.Sierra-Siegert@iop.kcl.ac.uk
authors.forename: M
authors.initials: M
authors.lastname: Sierra
authors.forename: F
authors.initials: F
authors.lastname: Lopera
authors.forename: M V
authors.initials: MV
authors.lastname: Lambert
authors.forename: M L
authors.initials: ML
authors.lastname: Phillips
authors.forename: A S
authors.initials: AS
authors.lastname: David
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology; D003861:Depersonalization / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D003937:Diagnosis, Differential; D004644:Emotions; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011936:Reality Testing; D014796:Visual Perception