title: Nociceptive withdrawal reflexes evoked by uniform-temperature laser heat stimulation of large skin areas in humans.
abstract: Nociceptive withdrawal reflexes (NWR) were evoked by brief (200 ms) painful CO(2) laser stimulation at five intensities (1.2, 1.4, 1.6, 1.8, and 2.0 x pain threshold) applied to nine sites (2 cm(2)) separated by 1.7 cm on the dorsal side of the foot and anterior part of the lower leg of 14 healthy volunteers. The purpose of the study was to investigate the characteristics of NWRs evoked by a natural stimulation modality. The reflexes were measured as the electromyographic response from the iliopsoas (ILI), quadriceps vastus lateralis (QVL), biceps femoris (BF), tibialis anterior (TA), and soleus (SOL) muscles. Stimulus-response relationships between heat intensity and the reflex magnitude and correlation between perceived pain intensity and reflex magnitude were observed in the ILI, QVL, BF, and TA but not the SOL. No significant differences in reflex magnitude were found between the stimulation sites. NWRs were evoked more often in flexor muscles than extensor muscles, indicating a non-site-specific reflex organization. The paper presents a new method to evoke NWRs by uniform-temperature laser heat stimulation of large skin areas in humans. These heat evoked reflexes had a stimulus-response relationship.
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark. cdahl@hst.aau.dk
authors.forename: Carsten Dahl
authors.initials: CD
authors.lastname: Mørch
authors.forename: Ole Kaeseler
authors.initials: OK
authors.lastname: Andersen
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004307:Dose-Response Relationship, Radiation; D004576:Electromyography / Q000379:methods; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D007834:Lasers; D008297:Male; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology* / Q000528:radiation effects; D011930:Reaction Time / Q000502:physiology* / Q000528:radiation effects; D012018:Reflex / Q000502:physiology*; D012867:Skin / Q000294:innervation* / Q000528:radiation effects