Seeing the piles of the velvet bending under our finger sliding over a tactile stimulator improves the feeling 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.

Experiment 1 : 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.

Files : data_brutes.csv and  ordre_xx_c.csv for data, Calculus_data_expe1.Rmd for code

Experiment 2 : Using electroencephalography and sources localization analyses, we found increased activity in the occipital and inferiorparietal lobes when seeing dark and shinning traces during back and forth finger
movements over the virtual surface. This suggests that these two posterior cortical regions work
together to evaluate visuo-tactile congruence between the seen and the felt (tactile). The visuotactile binding, evidenced by neural synchronization (specifically, theta band [5-7 Hz] oscillation) in the left inferior posterior parietal lobule, is consistent with enhanced integration of information and likely contributed to the emergence of a more realistic velvet representation. 

Files :  EEG time frequency individual data.xlsx and all .eeg