In

the present study, we indicated that the tactile electrical stimulation revealed the same relationship between stimulus intensity and cortical activation patterns as mixed nerve stimulation (Hoshiyama and Kakigi, 2001, Jousmaki and Forss, 1998, Torquati et al., 2002 and Tsutada et al., 1999). We observed two or three deflections for source activities at 28, 54 and 125 ms after MS, whereas four peaks were observed at 25, 41, 73, and 130 ms after ES. Moreover, the deflection of source activity approximately 28 ms after MS was obtained in only six of the twelve subjects, and when we calculated ECD location at the peak of the SEF waveform CT99021 cell line approximately 28 ms after MS, goodness-of-fit values above 90% were obtained from only two subjects. These results are consistent with previous studies using mechanical stimulation (Huttunen, 1986, Jousmaki et al., 2007 and Onishi et al., 2010). The differences in the waveform

for source activities elicited by MS relative to those elicited by ES may be accounted for by the following possibility. Extra time may be needed for skin indentation after the onset of MS or skin recovery after the offset of MS and the process of receptor transduction in the case of mechanical stimulation as pointed out by Nakanishi et al. (1973) and Hashimoto (1987). Another explanation may be that electrical stimulation with ring electrodes activated the digital nerves and receptors, which include cutaneous and joint afferents. This may differ from MS of the finger tip, which exclusively includes cutaneous afferents. However, this possibility could

not be clarified in the present study. Therefore, Fulvestrant we intend to perform further investigations to clarify this purported difference. The response of the secondary somatosensory cortex (S2) in the hemisphere ipsilateral to the stimulated side was not obtained by MS in the present study, although there have been Ergoloid some MEG studies on S2 responses following MS (Forss et al., 1994 and Onishi et al., 2010). The inter-stimulus interval (ISI) of stimulation was set at ≥1 s in these previous studies. Our main focus in the present study was to investigate the effect of the number of mechanical pins on S1 activity. To reduce the total experiment time for the participants, we used the stimulus rate of 2 Hz. Wikstrom et al. (1996) reported that the MEG response from S2 were seen only with an ISI of ≥1 s, beginning with the strongest responses seen using a 5 s ISI. Therefore, it was considered that the absence of S2 activities following MS might have been observed in the present study. In summary, we showed that in healthy humans, S1 activities in response to tiny mechanical pins on the index finger tip depend on the number of pins and the inter-pin distance. In addition, our results demonstrated that most source activities observed approximately 50 ms after MS with a tiny mechanical pin (1.3 mm diameter; height of the protrusion 0.8 mm; 2.