Aims: 

Different excitable tissues of skin react specifically to stimulation by electrical current with different properties (Kajimoto et. al., 1999). Our aim was to compare modality and localization of threshold sensations under cutaneous stimulation by alternating current (AC) of different frequencies.

Methods: 

Healthy volunteers (n = 180) of both sexes (18–22 years) were studied. The method of limits was used to detect absolute thresholds somatosensory sensations from electrical stimulation of left forearm skin by alternating current (AC) 0.1-50 mA at 30 Hz – 3 kHz AC frequencies (Bogdanov et al., 2004). The skin was stimulated through two flat 4 * 5 cm square silver electrodes separated by 10 cm on the left ventral forearm. The electrodes were applied to the skin with a gauze pad moistened with normal saline. Subjects reported the onset of the smallest detectable sensations and their modality and localization in the forearm.

Results: 

Under 0.03-0.10 kHz AC stimulation the probability of a nociceptive sensation (48.3-80.7%) and distal localization (50.3%) was the highest among other frequencies (p < 0.05 by t-test for each property). Under 0.3 kHz we observed the highest frequency of numbing effect in the palm (14.6%). Under 1- 3kHz the occurrence vibro-tactile modality (49.2-58.1%) and proximal localization (65.6%) were the highest among other frequency ranges.

Conclusion: 

The frequency of AC cutaneous stimulation affects both modality and localization of the sensations, that can be explained by a selective effect on either sensory endings or sensory nervous pathways.