title: Unconditioned and conditioned muscular responses in patients with chronic back pain and chronic tension-type headaches and in healthy controls.
abstract: Muscular tension is assigned an important role in the development and maintenance of chronic pain syndromes. It is seen as a psychophysiological correlate of learned fear and avoidance behavior. Basic theoretical models emphasize classical conditioning of muscular responses as a mechanism of pain chronification. However, the empirical basis for this field is very small. Our aim was to investigate muscular factors in relation to unconditioned and conditioned pain stimuli. An experimental study was conducted using a differential classical conditioning paradigm with 18 patients with chronic back pain (BP) and tension-type headache (TTH), and 18 healthy controls (HC). A high-pitched sound served as the CS+, paired with an intracutaneous electric pain stimulus (US), while a neutral sound was used as the CS-. Simultaneously, integrated surface electromyograms (iEMGs) were recorded for seven muscle sites. Our hypothesis was that the pain patients would demonstrate enhanced conditionability. Baseline values between patients (TTH, BP) and HC showed no significant differences. Although the perception and pain thresholds were balanced, both patient groups revealed a higher number of significant muscular responses to the pain stimulus (UR) than the HC. All participants showed significant conditioned muscular responses, however, the patients displayed a higher number than the healthy controls. Furthermore a significant relation was found between muscular responses and the experience of pain 1day after the experiment. Muscular responses can be learned via classical conditioning. TTH and BP patients revealed a higher number of unconditioned and conditioned responses.
authors.affiliation: Department of Psychology, Psychotherapeutic Outpatient Clinic Behavior Therapy, University of Hamburg, Von-Melle-Park 5, D-20146 Hamburg, Germany Spine Center, Klinikum Dortmund, Dortmund, Germany Department of Psychology, University of Hamburg, Germany Biosignal Processing and Neuro-Engineering, Institute for Signal Processing, University of Lübeck, Lübeck, Germany Department of Trauma Surgery, Schoen Klinik Hamburg, Germany.
authors.forename: Regine
authors.initials: R
authors.lastname: Klinger
authors.forename: Nadia
authors.initials: N
authors.lastname: Matter
authors.forename: Ralph
authors.initials: R
authors.lastname: Kothe
authors.forename: Bernhard
authors.initials: B
authors.lastname: Dahme
authors.forename: Ulrich G
authors.initials: UG
authors.lastname: Hofmann
authors.forename: Florian
authors.initials: F
authors.lastname: Krug
mesh_terms: D000704:Analysis of Variance; D001416:Back Pain / Q000503:physiopathology*; D003214:Conditioning, Classical / Q000502:physiology*; D004558:Electric Stimulation; D004562:Electrocardiography; D004576:Electromyography; D006801:Humans; D018482:Muscle, Skeletal / Q000503:physiopathology*; D017288:Pain Threshold / Q000502:physiology; D018781:Tension-Type Headache / Q000503:physiopathology*
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