D a midrange exemplar as a reference for the magnitude estimation test (Eadie and Doyle, 2002; Weismer and Laures, 2002). The result from the pilot experiment (see above) showed that the 7 stimulus was the midrange stimulus among each of the silicone stimuli. Participants touched the two references with their suitable index finger, one particular at a time beginning with the sham stimulus. They have been informed that the intensity values of stickiness were 0 and 70 for the sham and 7 stimuli, respectively, where the intensity values were arbitrarily assigned for quantification in our experiment. After this initial calibration, participants performed the trials of magnitude estimation. In each and every trial, participants first touched the two reference stimuli, followed by experiencing one of several eight stimuli (5 , 6 , 7 , 8 , 9 , 10 , 15 and 30 ), and Saccharin sodium Anti-infection verbally reported the perceived intensity of stickiness from the given stimulus. Participants had been instructed to report thefMRI ExperimentsAs this study aimed to discover brain regions underlying the tactile perception of stickiness, our investigation focused on the brain responses at the threshold of stickiness perception. Considering the fact that our pilot study indicated that tactile stickiness was perceived with all the stimuli with less than or equal towards the catalyst ratio of 7 , we chosen the 5 and six stimuli, including the 7 stimulus inside the test set. Amongst the stimuli greater than 7 , we chose the 8 and 30 stimuli, which corresponded to the minimum and maximum catalyst ratios, respectively. The 10 stimulus relating towards the regular catalyst ratio for PDMS was also added for the test stimulus set. Lastly, the acrylic sham stimulus was utilized for presenting a non-sticky stimulation. To sum up, the 5 , six , 7 , eight , ten and 30 silicone stimuli at the same time as the acrylic sham stimulus were applied for fMRI experiments to investigate neural responses for the stimuli with distinctive intensities of stickiness. Participants underwent two scanning sessions and T1 structure images were taken among the sessions. Through the functional image acquisition session, participants were comfortably laid inside a supine position though holding their ideal hand down around the MRI bed in a pronation position. They wore a MRI-compatible headphone to listen towards the directions in the course of the experiment. The participants’ heads had been fixed to prevent movement artifacts by inserting two foam cushions into the space in between the head plus the head coil. An event-related paradigm was adopted in our experiment. The procedure forFrontiers in Human Neuroscience | www.frontiersin.orgJanuary 2017 | Volume 11 | ArticleYeon et al.Neural Correlates of Tactile Stickinesseach trial is depicted in Figure 1. The stimulus presentation was carried out manually by an experimenter in the MRI space. Prior to a stimulus was offered, participants had been Nicotinamide riboside (malate) manufacturer relaxed together with the “Resting” finger position. Then, when participants heard the verbal instruction of the “Ready (“Jun-bee” in Korean)”, they attached their ideal index finger for the given stimulus and maintained the pose for 3 s till they heard a brief beep sound indicating for them to quit. Immediately after participants detached their finger in the stimulus at the beep sound, they stayed within the “Resting” posture again for 15 s until the following trial. Every single of your 7 stimuli was presented 10 times inside a random order, so that a single scanning session consisted of 70 trials. At the starting of every session, there was a 6-s interval and, hence, every session took approx.