Diurnal time course of pain perception in healthy humans

Objective: Rapid skin heating by infrared lasers can be used to investigate the integrity of the nociceptive system by activating Ad- and C-fibers. Laser-induced pain stimuli are sensed as dual pain sensation attributable to the two different fibers' conduction velocities. To date, only little is known about diurnal variation of laser-evoked pain perception and time course of laser-evoked potentials (LEP). Methods: We assessed circadian ad-fiber function by studying N2 and P2 components of LEPs and pain thresholds evoked by laser stimulation of the foot every two hours from 8 a.m. to 10 p.m. in 15 healthy subjec…