Frequency-Dependent Reduction of Cybersickness in Virtual Reality by Transcranial Oscillatory Stimulation of the Vestibular Cortex

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transcranial oscillatory stimulation cybersickness virtual reality vestibular system 10Hz neuromodulation motion sickness

Use of Transcranial Oscillatory Stimulation to Reduce Cybersickness in Virtual Reality

Background and Motivation
Virtual Reality (VR) technology is increasingly integrated into fields such as work, healthcare, and entertainment. However, approximately 95% of VR users experience symptoms known as Cybersickness (CS), characterized by nausea, dizziness, and discomfort. The root cause of this phenomenon lies in the persistent mismatch between visual, proprioceptive, and vestibular information, especially the illusion of “self-motion” (vection) triggered in virtual environments. Although VR technology has broad applications, the issue of CS limits its extensive adoption in medical rehabilitation, military training, and education. To address this challenge, researchers have developed a technology using transcranial alternating current stimulation (tACS) targeting the vestibular cortex to alleviate CS symptoms.

Research Source
This study was led by the research team at Siena Brain Investigation & Neuromodulation Lab, involving scientists from institutions such as the University of Siena, Massachusetts General Hospital, and Sapienza University. The paper was published in Neurotherapeutics (Volume 20, 2023), marking a significant breakthrough in the field of CS.

Methodology and Design

Research Procedures and Experimental Design

This study adopted a double-blind controlled experiment, recruiting 41 healthy young participants (25 male, 16 female, average age 26.5 years). The experiment included training and testing under three conditions (2 Hz tACS, 10 Hz tACS, and sham stimulation) to explore the effects of different tACS frequencies on CS symptoms. The detailed experimental steps are as follows:

  1. VR Scenario and CS Induction
    Participants were exposed to a virtual roller coaster scenario (Epic Rollercoaster) using Oculus Quest 2 headsets. During the 6-minute VR experience, participants sat passively and reported any onset of nausea or discomfort along with the duration.

  2. Application of Transcranial Oscillatory Stimulation
    tACS was delivered via electrodes targeting bilateral posterior insular vestibular cortex and posterior insular cortex. Based on SimNIBS modeling, current intensities were set at 2.5 mA and applied at 2 Hz and 10 Hz frequencies.

  3. Physiological and Behavioral Data Recording
    Galvanic Skin Response (GSR) was measured as an indicator of autonomic nervous activity, along with the duration of nausea and recovery time under each stimulation condition.

  4. Data Analysis
    Data were analyzed using Linear Mixed Models (LMMs), Spearman correlations, and linear regressions to explore relationships between variables.

Experimental Results

  1. Alleviation of CS Symptoms

    • Across the sample, 10 Hz tACS significantly reduced the duration of CS nausea (median reduction of approximately 0.84 log seconds). Among participants with potential for improvement, 67% reported symptom relief under 10 Hz, while 2 Hz tACS was significantly less effective.
    • Recovery time showed no significant differences across conditions.

  2. Autonomic Nervous System Responses

    • 10 Hz tACS decreased GSR (p < 0.001), indicating regulation of sympathetic nervous activity; in contrast, 2 Hz tACS increased GSR.
    • Changes in GSR suggest that tACS-induced CS improvements may be linked to autonomic nervous system modulation.

  3. Side Effects and Comfort

    • 2 Hz tACS caused more mild side effects (e.g., headaches, itching), while the differences in side effects between 10 Hz tACS and sham stimulation were not significant.

Conclusions and Implications

  1. Key Findings

    • This study demonstrated that 10 Hz tACS effectively reduces VR-induced CS symptoms, offering a novel approach to addressing issues related to vestibular dysfunction.
    • The frequency-specific effects of 10 Hz tACS in modulating slow-wave activity in the vestibular cortex highlight its potential mechanism of action.

  2. Scientific and Practical Significance

    • The findings hold substantial significance for mitigating CS, particularly in scenarios such as VR-based education, military training, and space exploration. Moreover, the technique may be applicable to treating other vestibular dysfunctions.
    • The portability and simplicity of tACS devices suggest their potential use in the metaverse for social, educational, and recreational applications.

  3. Limitations and Future Directions

    • The current study did not verify long-term effects on recovery time, necessitating future research into extended or repeated applications.
    • Future studies should explore personalized frequency optimization (e.g., based on alpha wave activity) and the integration of tACS with other neuromodulation techniques.

Research Highlights
This study validated the potential of tACS technology for alleviating CS and demonstrated, for the first time, the modulation of the vestibular cortex using 10 Hz oscillatory stimulation. The results not only advance our understanding of the neurophysiological mechanisms underlying CS but also provide innovative solutions for enhancing VR user experience. These findings open new possibilities for VR applications in complex environments and the treatment of related disorders.