title: Dynamic spectral indices of the electroencephalogram provide new insights into tonic pain.
abstract: OBJECTIVE
  This study aimed to investigate reliability of electroencephalography (EEG) during rest and tonic pain. Furthermore, changes in EEG between the two states as well as dynamics and relation to pain ratings were investigated.
  
  
  METHODS
  On two separate days EEG was recorded in 39 subjects during rest and tonic pain (cold pressor test: left hand held in 2°C water for 2 min.) while pain intensity was rated continuously. Dynamic spectral analysis was performed on the EEG. Between-day reliability of spectral indices was assessed and correlations to pain ratings were investigated.
  
  
  RESULTS
  EEG reliability was high during both states. The relative spectral indices increased in delta (1-4 Hz; P=0.0002), beta3 (18-32 Hz; P<0.0001) and gamma (32-70 Hz; P<0.0001) bands during tonic pain, and decreased in theta (4-8 Hz; P<0.0001), alpha1 (8-10 Hz; P<0.0001), alpha2 (10-12 Hz; P<0.0001) bands. Theta, beta3 and gamma bands correlated significantly to the area-under-curve of pain ratings, but only theta was dynamic and correlated to the pain ratings (R=0.88, P<0.0001).
  
  
  CONCLUSIONS
  EEG assessed during tonic pain is a valid experimental pain model both in terms of reliability between days and in connection between cortical activity and pain perception.
  
  
  CONCLUSIONS
  EEG during tonic pain is more pain-specific and should be used in future basic and pharmacological studies.
authors.affiliation: Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Gram
authors.affiliation: Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark; Mech-Sense, Department of Radiology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Graversen
authors.affiliation: Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: S S
authors.initials: SS
authors.lastname: Olesen
authors.affiliation: Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark; Center for Sensory-Motor Interactions (SMI), Department of Health Science and Technology, Aalborg University, Denmark. Electronic address: amd@mech-sense.com.
authors.forename: A M
authors.initials: AM
authors.lastname: Drewes
mesh_terms: D000328:Adult; D003080:Cold Temperature / Q000009:adverse effects; D004569:Electroencephalography / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000175:diagnosis* / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods* / Q000592:standards; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Cold pressor; Dynamics; EEG; Pain; Reliability; Theta; Tonic