Seeing the piles of the velvet bending under our finger sliding over a tactile stimulator improves the perception of the fabric

Using friction modulation to simulate fabrics with a tactile stimulator (i.e. virtual surface) is not sufficient to render fabric touch and even more so for hairy fabrics. We hypothesized that seeing the pile of the velvet darken or lighten depending on changes in the finger movement direction on the virtual surface should improve the velvet fabric rendering. Participants actively rubbed a tactile device or a velvet fabric looking at a screen that showed a synthesized image of a velvet which either remained static (V-static) or darkening/lightening with the direction of touch (V-moving). We showed that in V-moving condition, the touched surface was always perceived rougher, which is a descriptor of a real velvet (Experiment 1). Using electroencephalography and sources localization analyses, we found greater theta band [5-7 Hz] oscillation power in the left inferior posterior parietal lobule (PPC) in the Virtual velvet/V-moving condition as compared to both Real velvet/ V-static and Virtual velvet/V-static conditions (Experiment 2). This result is consistent with studies that give a crucial role to the left PPC for visuo-tactile binding. The greater activity of the lateral occipital area found in the Virtual velvet/V-moving condition could have contributed to the emergence of a velvet more realistic representation.