title: Altered functional connectivity and performance variability in relapsing-remitting multiple sclerosis.
abstract: BACKGROUND
  Patients with multiple sclerosis (MS) demonstrate slower and more variable performance on attention and information processing speed tasks. Greater variability in cognitive task performance has been shown to be an important predictor of neurologic status and provides a unique measure of cognitive performance in MS patients.
  
  
  OBJECTIVE
  This study investigated alterations in resting-state functional connectivity associated with within-person performance variability in MS patients.
  
  
  METHODS
  Relapsing-remitting MS patients and matched healthy controls completed structural MRI and resting-state fMRI (rsfMRI) scans, as well as tests of information processing speed. Performance variability was calculated from reaction time tests of processing speed. rsfMRI connectivity was investigated within regions associated with the default mode network (DMN). Relations between performance variability and functional connectivity in the DMN within MS patients were evaluated.
  
  
  RESULTS
  MS patients demonstrated greater reaction time performance variability compared to healthy controls (p<0.05). For MS patients, more stable performance on a complex processing speed task was associated with greater resting-state connectivity between the ventral medial prefrontal cortex and the frontal pole.
  
  
  CONCLUSIONS
  Among MS patients, greater functional connectivity between medial prefrontal and frontal pole regions appears to facilitate performance stability on complex speed-dependent information processing tasks.
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, Canada.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Wojtowicz
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Canada.
authors.forename: Erin L
authors.initials: EL
authors.lastname: Mazerolle
authors.affiliation: Department of Medicine, Dalhousie University, Canada.
authors.forename: Virender
authors.initials: V
authors.lastname: Bhan
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, Canada Department of Medicine, Dalhousie University, Canada Psychology, QEII Health Sciences Centre, Canada Department of Psychiatry, Dalhousie University, Canada john.fisk@cdha.nshealth.ca.
authors.forename: John D
authors.initials: JD
authors.lastname: Fisk
mesh_terms: D000328:Adult; D000368:Aged; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000503:physiopathology*; D009483:Neuropsychological Tests; D011930:Reaction Time
keywords: Multiple sclerosis; default mode network; functional connectivity; information processing speed; intra-individual variability; resting state fMRI