D a midrange exemplar as a reference for the magnitude estimation test (Eadie and Doyle, 2002; Weismer and Laures, 2002). The result in the pilot experiment (see above) showed that the 7 stimulus was the midrange stimulus amongst all of the silicone stimuli. Participants touched the two references with their ideal index finger, 1 at a time starting with all the sham stimulus. They had been informed that the intensity values of stickiness had been 0 and 70 for the sham and 7 stimuli, respectively, exactly where the intensity values had been arbitrarily assigned for quantification in our experiment. Right after this initial calibration, participants performed the trials of magnitude estimation. In each and every trial, participants initially touched the two reference stimuli, followed by experiencing one of Cuminaldehyde Purity & Documentation several eight stimuli (five , 6 , 7 , 8 , 9 , ten , 15 and 30 ), and verbally reported the perceived intensity of stickiness of the given stimulus. Participants had been instructed to report thefMRI ExperimentsAs this study aimed to find brain regions underlying the tactile perception of stickiness, our investigation focused around the brain responses at the threshold of stickiness perception. Given that our pilot study indicated that tactile stickiness was perceived together with the stimuli with much less than or equal towards the catalyst ratio of 7 , we selected the five and six stimuli, including the 7 stimulus within the test set. Among the stimuli higher than 7 , we chose the 8 and 30 stimuli, which corresponded to the minimum and maximum catalyst ratios, respectively. The 10 stimulus relating for the standard catalyst ratio for PDMS was also added to the test stimulus set. Lastly, the acrylic sham stimulus was utilized for presenting a non-sticky stimulation. To sum up, the 5 , 6 , 7 , 8 , ten and 30 silicone stimuli also because the acrylic sham stimulus were employed for fMRI experiments to investigate neural responses to the stimuli with different intensities of stickiness. Participants underwent two scanning sessions and T1 structure photos have been taken involving the sessions. Through the functional image acquisition session, participants have been comfortably laid inside a supine position although holding their appropriate hand down on the MRI bed inside a pronation position. They wore a MRI-compatible headphone to listen towards the guidelines through the experiment. The participants’ heads have been fixed to stop movement artifacts by inserting two foam cushions into the space among the head and also 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 inside the MRI area. Before a stimulus was provided, participants have been relaxed with the “Resting” finger position. Then, when participants heard the verbal instruction from the “Ready (“Jun-bee” in Korean)”, they attached their appropriate index finger for the offered stimulus and maintained the pose for 3 s till they heard a brief beep sound indicating for them to stop. Just after participants detached their finger in the stimulus in the beep sound, they stayed within the “Resting” posture once more for 15 s until the following trial. Every single with the 7 stimuli was presented 10 times inside a random order, in order that a single scanning session consisted of 70 trials. At the beginning of each session, there was a 6-s interval and, therefore, each and every session took approx.