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DOI: 10.1101/2023.05.22.540983

Modulation of visually induced self-motion illusions by alpha transcranial electric stimulation over the superior parietal cortex

S.Harquel C. Cian L. Torlay ...+3 M. Guerraz
Growing popularity of virtual reality systems has led to a renewed interest in understanding the neurophysiological correlates of the illusion of self-motion (vection), a phenomenon that can be both intentionally induced or avoided in such systems, depending on the application. Recent research has highlighted the modulation of [a] power oscillations over the superior parietal cortex during vection, suggesting the occurrence of inhibitory mechanisms in the sensorimotor and vestibular functional networks to resolve the inherent visuo-vestibular conflict. The present study aims to further explore this relationship and investigate whether neuromodulating these waves could causally affect the quality of vection. In a crossover design, 22 healthy volunteers received 13 minutes of high-amplitude, focused alpha-tACS over the superior parietal cortex while experiencing visually induced vection triggered by optokinetic stimulation. The tACS was tuned to each participant's individual alpha peak frequency, with theta-tACS and sham stimulation serving as controls. Overall, participants experienced better quality vection during alpha-tACS compared to control theta-tACS and sham stimulations, as quantified by the intensity of vection. The observed neuromodulation supports a causal relationship between parietal alpha oscillations and visually induced self-motion illusions, with their entrainment triggering over-inhibition of the conflict within the sensorimotor and vestibular functional networks. These results confirm the potential of non-invasive brain stimulation for modulating visuo-vestibular conflicts, which could help to enhance the sense of presence in virtual reality environments.