The 980-nm diode laser as a new stimulant for laser evoked potentials studies

Lasers have been used as stimulators for creating pain response without stimulating mechanoreceptive fibers. Various laser systems are still under investigation on the quest for best laser system. Our objective was to test the feasibility of the 980-nm diode laser for LEP (laser evoked potentials) studies.

Laser evoked potentials created by using the 980-nm diode laser were recorded by using standard electroencephalogram (EEG) techniques. The collimated laser beam was 3 mm in diameter. Stimulus duration was set to 200 msec. The power of laser stimulus exposed to the dorsum of the right hand of 10 healthy volunteer subjects (5 women and 5 men) was varied between 0 and 10 watts to determine the pain threshold. EEG signals during the exposure of 1.5 times the threshold value were recorded from scalp electrodes placed on areas Fz, Cz, Pz, C3, and C4 according to the international 10--20 system. The stimulus presented during the EEG recording was described as a bearable pain sensation like a pinprick perception by the subjects. After 0.1--30 Hz analog low-pass filtering, 100-msec prestimulus, and 900-msec poststimulus EEG epochs were recorded at 256 Hz sampling rate and evaluated statistically. Thirty stimuli were presented by randomly varying the interstimulus duration between 5 and 9 seconds.

Latency and amplitude values of LEPs were found in accordance with those reported in the literature.

The 980-nm diode laser used is a suitable stimulator for LEP studies.