title: Altered Effective Connectivity during a Processing Speed Task in Individuals with Multiple Sclerosis.
abstract: OBJECTIVE
  Processing speed impairment is the most prevalent cognitive deficit in individuals with multiple sclerosis (MS). However, the neural mechanisms associated with processing speed remain under debate. The current investigation provides a dynamic representation of the functioning of the brain network involved in processing speed by examining effective connectivity pattern during a processing speed task in healthy adults and in MS individuals with and without processing speed impairment.
  
  
  METHODS
  Group assignment (processing speed impaired vs. intact) was based on participants' performance on the Symbol Digit Modalities test (Parmenter, Testa, Schretlen, Weinstock-Guttman, & Benedict, 2010). First, brain regions involved in the processing speed task were determined in healthy participants. Time series from these functional regions of interest of each group of participants were then subjected to the effective connectivity analysis (Independent Multiple-Sample Greedy Equivalence Search and Linear, Non-Gaussian Orientation, Fixed Structure algorithms) that showed causal influences of one region on another during task performance.
  
  
  RESULTS
  The connectivity pattern of the processing speed impaired group was significantly different from the connectivity pattern of the processing speed intact group and of the healthy control group. Differences in the strength of common connections were also observed.
  
  
  CONCLUSIONS
  Effective connectivity results reveal that MS individuals with processing speed impairment not only have connections that differ from healthy participants and MS individuals without processing speed impairment, but also have increased strengths of connections.
authors.affiliation: 1Kessler Foundation,Pleasant Valley Way,West Orange,New Jersey.
authors.forename: E
authors.initials: E
authors.lastname: Dobryakova
authors.affiliation: 2Rutgers,New Jersey Medical School,Newark,New Jersey.
authors.forename: S L
authors.initials: SL
authors.lastname: Costa
authors.affiliation: 2Rutgers,New Jersey Medical School,Newark,New Jersey.
authors.forename: G R
authors.initials: GR
authors.lastname: Wylie
authors.affiliation: 1Kessler Foundation,Pleasant Valley Way,West Orange,New Jersey.
authors.forename: J
authors.initials: J
authors.lastname: DeLuca
authors.affiliation: 2Rutgers,New Jersey Medical School,Newark,New Jersey.
authors.forename: H M
authors.initials: HM
authors.lastname: Genova
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology*; D001931:Brain Mapping; D003072:Cognition Disorders / Q000000981:diagnostic imaging / Q000209:etiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications* / Q000000981:diagnostic imaging; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology*; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology
chemical_list: D010100:Oxygen
keywords: Attention; Causal connections; Cognitive deficits; Fronto-parietal network; Multiple sclerosis; Processing speed