Brain Activity During Electrical Stimulation of Visual-Motor Illusion with Enhanced Joint Motion Intensity

Visual-motor illusion (VMI) is a kinesthetic illusion produced by viewing an image showing joint motion. VMI with enhanced joint movement intensity (power-VMI; P-VMI) is expected to activate a wide range of motor association brain regions, and when combined with electrical stimulation that activates the motor sensory cortex, further activation of brain activity can be expected. This study aimed to verify the effectiveness of VMI using functional near-infrared spectroscopy to confirm brain activity during combined P-VMI and electrical stimulation. Brain activity was measured in 15 healthy adults during three tasks performed on the left ankle joint: P-VMI with electrical stimulation, P-VMI alone, and electrical stimulation alone. The tasks were performed randomly on a single participant. Brain activity was measured during each task using a protocol comprising 15 s of rest, 30 s of task performance, and 30 s of follow-up. Regions of interest included motor-related areas. The results showed that P-VMI alone activated the right superior parietal lobule and left supramarginal gyrus more than P-VMI combined with electrical stimulation. These findings suggest that P-VMI and sensory-threshold electrical stimulation do not necessarily complement each other in enhancing brain activity, as P-VMI alone shows greater activation in specific motor-related brain regions.