Photo showing the experimental set-up.

<p>The subject is sitting with the arm/hand and leg/foot, respectively in a relaxed position (A). The investigated skin area (index or little finger, head or the first or fifth metatarsal bone or heel) is placed on a vibrating probe (insert). The subject regulates the intensity of the vibration by pressure a button on a remote control (arrow) in his/her contralateral hand (B). The result is a tactilogram (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119753#pone.0119753.g002" target="_blank">Fig. 2</a>). The probe for the foot is shown in (C) and the green light (D) indicates that the pressure is appropriate on the investigated area. The person on the photo is <i>not</i> one of the subjects in the study.