Modulation of the cutaneous and cortical silent period in response to local menthol application

Abstract

In this study, we investigated the effects of menthol application on the cortical and cutaneous silent period (CSP/cutSP). Both the cutSP and CSP were assessed while participants (n = 11, young adults) exerted a light contraction with the right thumb. In the 1st block of trials, SPs were measured after the application of a Neutral gel (Aloe Vera) to the dorsal aspect of the hand. In the 2nd block, the same measures were repeated following a Menthol gel (4%) application. Subjective ratings of cooling sensations were obtained for each block. The Neutral gel was consistently perceived as slightly cool by participants, wheres the Menthol gel elicited sensations from cool to very cold. Paired t-tests showed no difference in the cutSP duration between the two conditions, whereas a significant increase in the CSP was detected with the Menthol condition. No correlation was found between changes in the CSP and those of the cutSP. These results highlight the difference between the cutSP and the CSP, as inhibitory phenomena, and point to a cortical contribution to the soothing effects associated with topical menthol applications.

Keywords:

• Menthol
• cold stimulation
• corticomotor excitability
• motor cortex

Acknowledgements

The authors wish to thank all participants for their time and patience during testing. Thanks to Katarina Hosel for technical assistance in testing sessions. R.K.’s involvement in this project was through participation in the Undergraduate Research Opportunity Program at the University of Ottawa.