title: Discrepancy between perceived pain and cortical processing: A voxel-based morphometry and contact heat evoked potential study.
abstract: OBJECTIVE
  The purpose of this study was to determine if local gray and white matter volume variations between subjects could account for variability in responses to CHEP stimulation.
  
  
  METHODS
  Structural magnetic resonance imaging was used to perform voxel-based morphometry (VBM) of gray and white matter in 30 neurologically healthy subjects. Contact heat stimulation was performed on the dorsum of the right hand at the base of the thumb. Evoked potentials were acquired from a vertex-recording electrode referenced to linked ears.
  
  
  RESULTS
  Controlling for age, total intracranial volume, and skull/scalp thickness, CHEP amplitude and pain rating were not significantly correlated between subjects. A VBM region of interest approach demonstrated a significant interaction between pain rating and N2 amplitude in the right insular cortex (p<0.05, family-wise error corrected, FWE). In white matter, a significant interaction was localized in the right inferior frontal occipital fasciculus (IFOF, p<0.05 FWE).
  
  
  CONCLUSIONS
  Accounting for gray matter volume in the right insular cortex, resulted in a significant relationship between CHEP amplitude and pain rating.
  
  
  CONCLUSIONS
  This finding suggests that the discrepancy between pain ratings and the amplitude of evoked potentials is not solely related to measurement artifact, but rather attributable, in part, to anatomical differences between subjects.
authors: Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland; The Hulse Spinal Cord Injury Laboratory, Shepherd Center, Atlanta, GA, USA; ICORD/School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address: kramer@icord.org.
authors: J L K
authors: JLK
authors: Kramer
authors: Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland.
authors: C R
authors: CR
authors: Jutzeler
authors: Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland; Brain and Spinal Injury Center, Department of Neurological Surgery, University of California, San Francisco, USA.
authors: J
authors: J
authors: Haefeli
authors: Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland.
authors: A
authors: A
authors: Curt
authors: Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland; Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, UK; Department of Brain Repair & Rehabilitation, UCL Institute of Neurology, University College London, UK.
authors: P
authors: P
authors: Freund
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods* / Q000523:psychology; D005260:Female; D066128:Gray Matter / Q000033:anatomy & histology* / Q000473:pathology / Q000502:physiology; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008297:Male; D009929:Organ Size; D010146:Pain / Q000175:diagnosis / Q000523:psychology; D010147:Pain Measurement / Q000379:methods* / Q000523:psychology; D058748:Pain Perception / Q000502:physiology; D066127:White Matter / Q000033:anatomy & histology* / Q000473:pathology / Q000502:physiology; D055815:Young Adult
keywords: Contact heat evoked potentials; Gray matter; Inferior frontal occipital fasciculus; Insular; Laser evoked potentials; White matter