title: Deficits in agency in schizophrenia, and additional deficits in body image, body schema, and internal timing, in passivity symptoms.
abstract: Individuals with schizophrenia, particularly those with passivity symptoms, may not feel in control of their actions, believing them to be controlled by external agents. Cognitive operations that contribute to these symptoms may include abnormal processing in agency as well as body representations that deal with body schema and body image. However, these operations in schizophrenia are not fully understood, and the questions of general versus specific deficits in individuals with different symptom profiles remain unanswered. Using the projected-hand illusion (a digital video version of the rubber-hand illusion) with synchronous and asynchronous stroking (500 ms delay), and a hand laterality judgment task, we assessed sense of agency, body image, and body schema in 53 people with clinically stable schizophrenia (with a current, past, and no history of passivity symptoms) and 48 healthy controls. The results revealed a stable trait in schizophrenia with no difference between clinical subgroups (sense of agency) and some quantitative (specific) differences depending on the passivity symptom profile (body image and body schema). Specifically, a reduced sense of self-agency was a common feature of all clinical subgroups. However, subgroup comparisons showed that individuals with passivity symptoms (both current and past) had significantly greater deficits on tasks assessing body image and body schema, relative to the other groups. In addition, patients with current passivity symptoms failed to demonstrate the normal reduction in body illusion typically seen with a 500 ms delay in visual feedback (asynchronous condition), suggesting internal timing problems. Altogether, the results underscore self-abnormalities in schizophrenia, provide evidence for both trait abnormalities and state changes specific to passivity symptoms, and point to a role for internal timing deficits as a mechanistic explanation for external cues becoming a possible source of self-body input.
authors.affiliation: Pharmacology, Pharmacy and Anaesthesiology Unit, School of Medicine and Pharmacology, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia , Perth, WA , Australia ; Statewide Department of Neurophysiology and Clinical Research Centre, Graylands Hospital, North Metropolitan Health Services - Mental Health , Perth, WA , Australia.
authors.forename: Kyran T
authors.initials: KT
authors.lastname: Graham
authors.affiliation: Pharmacology, Pharmacy and Anaesthesiology Unit, School of Medicine and Pharmacology, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia , Perth, WA , Australia ; Statewide Department of Neurophysiology and Clinical Research Centre, Graylands Hospital, North Metropolitan Health Services - Mental Health , Perth, WA , Australia.
authors.forename: Mathew T
authors.initials: MT
authors.lastname: Martin-Iverson
authors.affiliation: Centre for Integrative Neuroscience and Neurodynamics, School of Psychology and Clinical Language Sciences, University of Reading , Reading , UK.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Holmes
authors.affiliation: Centre for Clinical Research in Neuropsychiatry, School of Psychiatry and Clinical Neurosciences, The University of Western Australia , Perth, WA , Australia.
authors.forename: Assen
authors.initials: A
authors.lastname: Jablensky
authors.affiliation: Statewide Department of Neurophysiology and Clinical Research Centre, Graylands Hospital, North Metropolitan Health Services - Mental Health , Perth, WA , Australia ; Centre for Clinical Research in Neuropsychiatry, School of Psychiatry and Clinical Neurosciences, The University of Western Australia , Perth, WA , Australia.
authors.forename: Flavie
authors.initials: F
authors.lastname: Waters
keywords: agency; body image; body schema; first-rank symptoms; hand laterality; passivity symptoms; rubber-hand illusion; schizophrenia