title: Real world referencing and schizophrenia: are we experiencing the same reality?
abstract: Psychotic symptoms in schizophrenia patients encompass the difficulty to distinguish between the respective points of view of self and others. The capacity to adopt and switch between different perspectives is, however, fundamental for ego- and allocentric spatial referencing. We tested whether schizophrenia patients are able to adopt and maintain a non-egocentric point of view in a complex visual environment. Twenty-four chronic schizophrenic outpatients (11 females) and 25 controls matched for age, gender, years of education and handedness were recruited from a population-based sample. In a virtual environment, participants had to make a decision as to which of two trash cans was closest to themselves (viewer-centered, egocentric), to a ball (object-centered, unstable allocentric), or to a palace (landmark-centered, stable allocentric). Main outcome measures were reaction time, error rate, learning rate and local task switch cost. While egocentric reaction time was preserved, patients showed an increased reaction time in both allocentric referencing conditions (stable and unstable) and an overall increased error rate. Switch cost was diminished in patients when changing from the egocentric to the landmark-centered condition and elevated when changing from the landmark-centered to the egocentric condition. The results imply that schizophrenia patients' adoption of an egocentric perspective is preserved. However, adopting an allocentric point of view and switching between egocentric and landmark-centered perspectives are impaired. Perturbations in non-egocentric referencing and transferring efficiently between different referential systems might contribute to altered personal and social world comprehension in schizophrenia.
authors.affiliation: Department of Psychology, Humboldt University, Rudower Chaussee 18, 12489 Berlin, Germany. Steffen.Landgraf@inserm.fr
authors.forename: Steffen
authors.initials: S
authors.lastname: Landgraf
authors.forename: Marie-Odile
authors.initials: MO
authors.lastname: Krebs
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Olié
authors.forename: Giorgia
authors.initials: G
authors.lastname: Committeri
authors.forename: Elke
authors.initials: E
authors.lastname: van der Meer
authors.forename: Alain
authors.initials: A
authors.lastname: Berthoz
authors.forename: Isabelle
authors.initials: I
authors.lastname: Amado
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D011936:Reality Testing; D012559:Schizophrenia / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D013028:Space Perception / Q000502:physiology*; D055815:Young Adult