title: Reward responsiveness in patients with chronic pain.
abstract: BACKGROUND
  It is proposed that changes in reward processing in the brain are involved in the pathophysiology of pain based on experimental studies. The first aim of the present study was to investigate if reward drive and/or reward responsiveness was altered in patients with chronic pain (PCP) compared to controls matched for education, age and sex. The second aim was to investigate the relationship between reward processing and nucleus accumbens volume in PCP and controls. Nucleus accumbens is central in reward processing and its structure has been shown to be affected by chronic pain conditions in previous studies.
  
  
  METHODS
  Reward drive and responsiveness were assessed with the Behavioral Inhibition Scale/Behavioral Activation Scale, and nucleus accumbens volumes obtained from T1-weighted brain MRIs obtained at 3T in 19 PCP of heterogeneous aetiologies and 20 age-, sex- and education-matched healthy controls. Anhedonia was assessed with Beck's Depression Inventory II.
  
  
  RESULTS
  The PCP group had significantly reduced scores on the reward responsiveness, but not reward drive. There was a trend towards smaller nucleus accumbens volume in the PCP compared to control group. There was a significant positive partial correlation between reward responsiveness and nucleus accumbens volume in the PCP group adjusted for anhedonia, which was significantly different from the same relationship in the control group.
  
  
  CONCLUSIONS
  Reward responsiveness is reduced in chronic pain patients of heterogeneous aetiology, and this reduction was associated with nucleus accumbens volume. Reduced reward responsiveness could be a marker of chronic pain vulnerability, and may indicate reduced opioid function.
authors.affiliation: Department of Neuroscience, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
authors.forename: N A
authors.initials: NA
authors.lastname: Elvemo
authors.affiliation: Clinical Neuroscience Research Group, Department of Psychology, University of Oslo, Norway.|Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.|National Competence Centre for Complex Symptom Disorders, St. Olav's University Hospital, Trondheim, Norway.
authors.forename: N I
authors.initials: NI
authors.lastname: Landrø
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.|National Competence Centre for Complex Symptom Disorders, St. Olav's University Hospital, Trondheim, Norway.
authors.forename: P C
authors.initials: PC
authors.lastname: Borchgrevink
authors.affiliation: Department of Neuroscience, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.|Department of Medical Imaging, St. Olav's University Hospital, Trondheim, Norway.
authors.forename: A K
authors.initials: AK
authors.lastname: Håberg
mesh_terms: D000328:Adult; D059350:Chronic Pain / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009714:Nucleus Accumbens / Q000473:pathology*; D012201:Reward