Inferior Parietal Lobe Activity in Visuo-Motor Integration during the Robot Hand Illusion

The robot hand illusion (RoHI) is the participant’s illusion of the self-ownership and the self-agency of a robot hand that appears to be moving consistently with their own hand, and feel as if the robot hand belongs to them. Mismatching between motor and visual information disrupt the effect of RoHI respect to the robot hand. In our previous study, we found that participants felt that the virtual hand was their own when the visual feedback was delayed by less than 200 ms. Moreover, although they did not feel that the virtual hand was their own, the participants felt that they could control the virtual hand even with a visual delay of 300 - 500 ms. Here, we used near-infrared spectroscopy (NIRS) to investigate brain activity associated with the RoHI under different delayed visual feedback conditions (100 ms, 400 ms, and 700 ms). We found significant activation in the supramarginal gyrus and superior temporal gyrus in the 100 ms feedback delay condition. An ANOVA indicated that this activation was significantly different from that in other conditions (p < 0.01). These results demonstrate that activity in the inferior parietal cortex was modulated by the delay between the motor command and the visual feedback regarding the movement of the robot hand. We propose that the inferior parietal lobe is essential for integrating motor and visual information that enables one to distinguish their own body from those of others.