title: Vestibular stimulation improves insight into illness in schizophrenia spectrum disorders.
abstract: Impaired insight into illness (IMP-INS) is common among individuals with schizophrenia spectrum disorders (SSD), contributing to medication nonadherence and poor clinical outcomes. Caloric vestibular simulation (CVS) is typically used to assess peripheral vestibular system function. Left cold CVS is also a transiently effective treatment for IMP-INS and hemineglect secondary to right brain hemisphere stroke, and possibly for IMP-INS and mood stabilization in patients with SSD. Participants with SSD and moderate-to-severe IMP-INS participated in an exploratory double blind, crossover, randomized controlled study of the effects of CVS on IMP-INS. Participants sequentially received all experimental conditions-left cold (4°C), right cold, and body temperature/sham CVS-in a random order. Repeated measures ANOVA were performed to compare changes in IMP-INS, mood and positive symptom severity pre and 30min post CVS. A significant interaction was found between CVS condition, time, and body temperature nystagmus peak slow phase velocity (PSPV) for IMP-INS, indicating that single session left cold CVS transiently improved IMP-INS while right cold CVS may have worsened IMP-INS, particularly in participants with greater vestibular reactivity (i.e. higher PSPV) to body temperature CVS. The procedure's effectiveness is attributed to stimulation of underactive right hemisphere circuits via vestibular nuclei projections to the contralateral hemisphere.
authors.affiliation: Multimodal Imaging Group, Research Imaging Centre, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Geriatric Mental Health Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Campbell Mental Health Research Institute, Research Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada. Electronic address: philgerretsen@yahoo.com.
authors.forename: Philip
authors.initials: P
authors.lastname: Gerretsen
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada; Centre for Advanced Hearing and Balance Testing, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: David D
authors.initials: DD
authors.lastname: Pothier
authors.affiliation: Centre for Advanced Hearing and Balance Testing, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Falls
authors.affiliation: Centre for Advanced Hearing and Balance Testing, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Maxine
authors.initials: M
authors.lastname: Armstrong
authors.affiliation: Multimodal Imaging Group, Research Imaging Centre, Centre for Addiction & Mental Health, Toronto, Ontario, Canada.
authors.forename: Thushanthi
authors.initials: T
authors.lastname: Balakumar
authors.affiliation: Geriatric Mental Health Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Uchida
authors.affiliation: Multimodal Imaging Group, Research Imaging Centre, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Department of Psychiatry, Faculties of Medicine and Health Science, University of Malta, Msida, Malta.
authors.forename: David C
authors.initials: DC
authors.lastname: Mamo
authors.affiliation: Multimodal Imaging Group, Research Imaging Centre, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Geriatric Mental Health Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Campbell Mental Health Research Institute, Research Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Pollock
authors.affiliation: Multimodal Imaging Group, Research Imaging Centre, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Geriatric Mental Health Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Campbell Mental Health Research Institute, Research Program, Centre for Addiction & Mental Health, Toronto, Ontario, Canada; Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Ariel
authors.initials: A
authors.lastname: Graff-Guerrero
mesh_terms: D000328:Adult; D000377:Agnosia / Q000503:physiopathology* / Q000523:psychology / Q000628:therapy*; D001364:Awareness / Q000502:physiology*; D002150:Caloric Tests; D016022:Case-Control Studies; D003717:Denial, Psychological; D004292:Dominance, Cerebral / Q000502:physiology; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000503:physiopathology* / Q000628:therapy*; D012559:Schizophrenia / Q000503:physiopathology* / Q000628:therapy*; D012565:Schizophrenic Psychology; D012803:Sick Role; D016896:Treatment Outcome; D014722:Vestibule, Labyrinth / Q000503:physiopathology*
keywords: Anosognosia; Illness denial; Insight into illness; Schizophrenia; Vestibular stimulation