title: White matter alterations related to P300 abnormalities in individuals at high risk for psychosis: an MRI-EEG study.
abstract: BACKGROUND
  Psychosis onset is characterized by white matter and electrophysiologic abnormalities. The relation between these factors in the development of illness is almost unknown. We studied the relation between white matter volumes and P300 in prodromal psychosis.
  
  
  METHODS
  We assessed white matter volume (detected using magnetic resonance imaging) and electrophysiologic response during an oddball task (P300) in healthy controls and individuals at high clinical risk for psychosis (with an "at-risk mental state" [ARMS]).
  
  
  RESULTS
  We included 41 controls and 39 patients with an ARMS in our study. A psychotic disorder developed in 26% of the ARMS group within the follow-up period of 2 years. The P300 amplitude was significantly lower in the ARMS group than in the control group. The ARMS group showed reduced volume of white matter underlying the left superior temporal gyrus and the left superior frontal gyrus and increased volume of white matter underlying the right insula and the right angular gyrus compared with controls. Relative to individuals who did not later become psychotic, the subgroup in whom psychosis subsequently developed had a smaller volume of white matter underlying the left precuneus and the right middle temporal gyrus and increased volume in the white matter underlying the right middle frontal gyrus. We observed a significant interaction in the right middle frontal gyrus: white matter volume was negatively associated with P300 amplitude in the ARMS group and positively associated with P300 amplitude in the control group.
  
  
  CONCLUSIONS
  The voxel-based morphometry method alone cannot determine whether abnormal white matter volumes are due to an altered number of axonal connections or decreased myelination.
  
  
  CONCLUSIONS
  P300 abnormalities precede the onset of psychosis and are directly related to white matter alterations, representing a correlate of an increased vulnerability to disease.
authors.affiliation: Psychosis Clinical Academic Group, Institute of Psychiatry, King's Health Partners, King's College London, London, UK. p.fusar@libero.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Fusar-Poli
authors.forename: Nicolas
authors.initials: N
authors.lastname: Crossley
authors.forename: James
authors.initials: J
authors.lastname: Woolley
authors.forename: Francesco
authors.initials: F
authors.lastname: Carletti
authors.forename: Rocio
authors.initials: R
authors.lastname: Perez-Iglesias
authors.forename: Matthew
authors.initials: M
authors.lastname: Broome
authors.forename: Louise
authors.initials: L
authors.lastname: Johns
authors.forename: Paul
authors.initials: P
authors.lastname: Tabraham
authors.forename: Elvira
authors.initials: E
authors.lastname: Bramon
authors.forename: Philip
authors.initials: P
authors.lastname: McGuire
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D001931:Brain Mapping / Q000379:methods; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology* / Q000502:physiology; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000175:diagnosis / Q000473:pathology* / Q000503:physiopathology; D012307:Risk Factors