Disruption by virtual reality of the cortical oscillations related to visuotactile integration during an embodiment process
Virtual reality (VR) enables fast, free, and highly controllable experimental body image setting. Illusions pertaining to a body, like the rubber hand illusion (RHI), can be easily conducted in VR settings, and some phenomena, such as full-body illusions, are only realized in virtual environments. However, the multisensory integration process in VR is not yet fully understood, and we must clarify the limitations and whether specific phenomena can also occur in real life or only in VR settings. One useful investigative approach is measuring brain activities during a psychological experiment. Electroencephalography (EEG) oscillatory activities provide insight into the human multisensory integration process. Unfortunately, the data can be vulnerable to VR noise, which causes measurement and analytical difficulties for EEG data recorded in VR environments. Here, we took care to provide an experimental RHI setting using a head-mounted display, which provided a VR visual space and VR dummy hand along with EEG measurements. We compared EEG data taken in both real and VR environments and observed the gamma and theta band oscillatory activities. Ultimately, we saw statistically significant differences between congruent (RHI) and incongruent (not RHI) conditions in the real environment, which agrees with previous studies. No difference in the VR condition could be observed, suggesting that the VR setting itself altered the perceptual and sensory integration mechanisms. Thus, we must model this difference between real and VR settings whenever we use VR to investigate our bodily self-perception.