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Humans are adept at perceiving textures through touch. Previous neuroimaging studies have identified a distributed network of brain regions involved in the tactile perception of texture. However, it remains unclear how nodes in this network contribute to the tactile awareness of texture. To examine the hypothesis that such awareness involves the interaction of the primary somatosensory cortex with higher order cortices, we conducted a functional magnetic resonance imaging (fMRI) study utilizing the velvet hand illusion, in which an illusory velvet-like surface is perceived between the hands. Healthy participants were subjected to a strong illusion, a weak illusion, and tactile perception of real velvet. The strong illusion induced greater activation in the primary somatosensory cortex (S1) than the weak illusion, and increases in such activation were positively correlated with the strength of the illusion. Furthermore, both actual and illusory perception of velvet induced common activation in S1. Psychophysiological interaction (PPI) analysis revealed that the strength of the illusion modulated the functional connectivity of S1 with each of the following regions: the parietal operculum, superior parietal lobule, precentral gyrus, insula, and cerebellum. The present results indicate that S1 is associated with the conscious tactile perception of textures, which may be achieved via interactions with higher order somatosensory areas.

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Falls and their related injuries pose a significant risk to human health. One of the most common falls, the forward fall, frequently occurs among adults and the elderly. In this study, we propose using a human body model, developed using the MAthematical DYnamic MOdel (MADYMO) software, in place of human subjects, to investigate forward fall-related injuries. The MADYMO human body model is capable of simulating items that cannot be assessed on human subjects, such as human kinematics, human dynamics, and the possibility of injuries. In order to achieve our goal, a set of experiments was conducted to measure the impact force during a worst-case forward fall scenario (the outstretched hand position) for two short fall heights. Similar to the experimental design used on the human subjects, we generated a MADYMO human model. After performing the simulations, the results of the experiment on the human subjects and the MADYMO simulation model were compared. We demonstrated a significant correlation between the MADYMO simulation and the human subject experiments with respect to the magnitude and timing of the impact forces. Consequently, we validated the MADYMO human body model as a means to accurately assess forward fall-related injuries. Additionally, we compared the predicted results of a mathematical model with the MADYMO human body model. The MADYMO model is reliable and can demonstrate an accurate impact time. Therefore, we conclude that the MADYMO human model can be utilized as a reliable model to investigate forward fall-related injuries from a typical standing position.

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