title: A hyper-connected but less efficient small-world network in the substance-dependent brain.
abstract: BACKGROUND
  The functional interconnections of the addicted brain may differ from the non-addicted population in important ways, but prioranalytic approaches were usually limited to the study of connections between a few number of selected brain regions. Recent approaches enable examination of the vast functional interactions within the entire brain, the functional connectome (FCM). The purpose of this study was to characterize FCM alterations in addiction using resting state functional Magnetic Resonance Imaging (rsfMRI) and to assess their relations to addiction-related symptoms.
  
  
  METHODS
  rsfMRI data were acquired from 20 chronic polydrug users whose primary diagnosis was cocaine dependence (DRUG) and 19 age-matched non-drug using healthy controls (CTL). FCM was assessed using graph theoretical analysis.
  
  
  RESULTS
  Among the assessed 90 brain subdivisions, DRUG showed stronger functional connectivity. After controlling functional connectivity difference and the resultant network density, DRUG showed reduced communication efficiency and reduced small-worldness.
  
  
  CONCLUSIONS
  The increased connection strength in drug users' brain suggests an elevated dynamic resting state that may enable a rapid, semi-automatic, execution of behaviors directed toward drug-related goals.The reduced FCM communication efficiency and reduced small-worldness suggest a loss of normal inter-regional communications and topology features that makes it difficult to inhibit the drug seeking behavior.
authors.affiliation: Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, China; Center for Cognition and Brain Disorders, Hangzhou Normal University, China; Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, USA. Electronic address: redhatw@gmail.com.
authors.forename: Ze
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, USA; VISN-4 Mental Illness Research, Education and Clinical Center, VA Medical Center, Philadelphia, PA 19104, USA.
authors.forename: Jesse
authors.initials: J
authors.lastname: Suh
authors.affiliation: Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, USA.
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Li
authors.affiliation: Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Franklin
authors.affiliation: Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: O'Brien
authors.affiliation: Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, USA.
authors.forename: Anna Rose
authors.initials: AR
authors.lastname: Childress
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D019970:Cocaine-Related Disorders / Q000503:physiopathology; D066249:Craving; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology*; D019966:Substance-Related Disorders / Q000503:physiopathology*
keywords: Drug addiction; Functional connectome; Resting state fMRI