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L-menthol is known to activate transient receptor potential melastatin 8 (TRPM8) and induce analgesia to thermal stimuli. However, since thermal stimulation leads to the interaction among the other TRP channels, it was unclear whether L-menthol causes analgesia to stimuli other than thermal stimuli. Therefore, we aimed to investigate whether activating TRPM8 via topical application of 10% menthol solution attenuates pain-related somatosensory-evoked potentials (pSEPs) and affects numerical rating scale (NRS) score using intra-epidermal electrical stimulation (IES). We applied 10% L-menthol or control solution on the dorsum of the right hand of 25 healthy participants. The pSEP and NRS, elicited by IES, and sensory threshold were measured before and after each solution was applied. The results showed that the topical application of 10% L-menthol solution significantly reduced N2–P2 amplitude in pSEPs compared with the control solution. Moreover, the N2 latency was significantly prolonged upon the topical application of L-menthol solution. NRS scores were similar under both conditions. These results suggest that topical application of L-menthol does not alter subjective sensation induced using IES, although it may attenuate afferent signals at free nerve endings even with stimuli that do not directly activate TRP channels. [ABSTRACT FROM AUTHOR]

Background and objectives: We examined sex differences in the excitatory and inhibitory functions of the primary somatosensory cortex (S1) between males and females during the early follicular phase, when estradiol hormones are unaffected. Methods: Fifty participants (25 males and 25 females) underwent measurement of somatosensory evoked potentials (SEPs) and paired-pulse inhibition (PPI) in the S1; SEPs and PPI were elicited by constant current square-wave pulses (0.2 ms duration) delivered to the right median nerve by electrical stimulation. Paired-pulse stimulation occurred at 30- and 100-ms interstimulus intervals. Participants were randomly presented with 1500 (500 stimuli each) single- and paired-pulse stimuli at 2 Hz. Results: The N20 amplitude was significantly larger in female subjects than in male subjects, and the PPI-30 ms was significantly potentiated in female subjects compared to that in male subjects. Conclusions: The excitatory and inhibitory functions in S1 differ between male and female subjects, at least during the early follicular phase. [ABSTRACT FROM AUTHOR]

Proactive inhibition is divided into two components: action postponing (AP), which refers to slowing the onset of response, and action restraint (AR), which refers to preventing the response. To date, several studies have reported alterations in proactive inhibition and its associated neural processing among sensory modalities; however, this remains inconclusive owing to several methodological issues. This study aimed to clarify the differences in AP and AR and their neural processing among visual, auditory, and somatosensory modalities using an appropriate experimental paradigm that can assess AP and AR separately. The postponing time calculated by subtracting simple reaction time from Go signal reaction time was shorter in the visual modality than in the other modalities. This was explained by faster neural processing for conflict monitoring induced by anticipating the presence of the No-go signal, supported by the shorter latency of AP-related N2. Furthermore, the percentage of false alarms, which is the reaction to No-go signals, was lower in the visual modality than in the auditory modality. This was attributed to higher neural resources for conflict monitoring induced by the presence of No-go signals, supported by the larger amplitudes of AR-related N2. Our findings revealed the differences in AP and AR and their neural processing among sensory modalities.