Comparative psychophysical characteristics of cutaneous CO2 laser and contact heat stimulation.
Psychophysical visual analog scaling can be used to reveal critical determinants of the neural processing underlying non-painful and painful heat sensations produced by radiant and contact heat stimulation. This study determined the stimulus-response (S-R) functions of cutaneous non-painful and painful heat stimuli delivered by an infra-red CO2 laser or by a contact thermode in a series of experiments in healthy volunteers. In experiments 1 (n = 12), with the rating scale anchored at pain threshold, the S-R curve for brief (60 ms) laser pulse stimulation with a beam diameter of 10 mm was a negatively accelerating function. Transformation of laser stimulus intensity (W) into temperatures (degree C) did not change the form of the S-R curve. In experiment 2 (n = 9), using the same laser stimulus parameters as in experiment 1, but without an anchored rating scale, the form of the S-R relationship did not change. In experiment 3 (n = 9), increases of the laser pulse duration up to 5 s and the beam diameter up to 18 mm produced linear S-R curves. In contrast, in experiment 4 (n = 21), the S-R curve for cutaneous contact heat stimuli applied for 5 s with an 18 mm diameter probe was best described by a positively accelerating power function with an exponent greater than 2.0. These experiments have (1) characterized the S-R functions for different parameters of infra-red laser stimulation of the skin, and (2) have shown that the form of the S-R function for innocuous and noxious heat sensation is influenced strongly by the physical conditions of heat stimulus application, including mechanical contact with the skin.
Svensson
P
P
Department of Prosthetic Dentistry and Stomatognathic Physiology, Royal Dental College, University of Aarhus, Denmark.
Rosenberg
B
B
Beydoun
A
A
Morrow
T J
TJ
Casey
K L
KL
D000293:Adolescent; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D005260:Female; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006801:Humans; D007834:Lasers; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D010525:Peripheral Nerves / Q000502:physiology; D011601:Psychophysics; D012016:Reference Values; D012867:Skin / Q000294:innervation*; D013823:Thermoreceptors / Q000502:physiology*; D013697:Thermosensing / Q000502:physiology*