Left parietal involvement in motion sickness susceptibility revealed by multimodal magnetic resonance imaging

Alpha tACS on Parieto-Occipital Cortex Mitigates Motion Sickness Based on Multiple Physiological Observation

Approximately one third of the population is prone to motion sickness (MS), which is associated with the dysfunction in the integration of sensory inputs. Transcranial alternating current stimulation (tACS) has been widely used to modulate neurological functions by affecting neural oscillation. However, it has not been applied in the treatment of motion sickness. This study aims to investigate changes in brain oscillations during exposure to MS stimuli and to further explore the potential impact of tACS with the corresponding frequency and site on MS symptoms. A total of 19 subjects were recruited to be exposed to Coriolis stimuli to complete an inducing session. After that, they were randomly assigned to tACS stimulation group or sham stimulation group to complete a stimulation session. Electroencephalography (EEG), electrocardiogram, and galvanic skin response were recorded during the experiment. All the subjects suffering from obvious MS symptoms after inducing session were observed that alpha power of four channels of parieto-occipital lobe significantly decreased (P7: t =3.589, p <0.001; P8: t =2.667, p <0.05; O1: t =3.556, p <0.001; O2: t =2.667, p <0.05). Based on this, tACS group received the tACS stimulation at 10Hz from Oz to CPz. Compared to sham group, tACS stimulation significantly improved behavioral performance and entrained the alpha oscillation in individuals whose alpha power decrease during the inducing session. The findings show that parieto-occipital alpha oscillation plays a critical role in the integration of sensory inputs, and alpha tACS on parieto-occipital can become a potential method to mitigate MS symptoms.

Investigating cortical activity during cybersickness by fNIRS

This study investigated brain responses during cybersickness in healthy adults using functional near-infrared spectroscopy (fNIRS). Thirty participants wore a head-mounted display and observed a virtual roller coaster scene that induced cybersickness. Cortical activation during the virtual roller coaster task was measured using fNIRS. Cybersickness symptoms were evaluated using a Simulator Sickness Questionnaire (SSQ) administered after the virtual rollercoaster. Pearson correlations were performed for cybersickness symptoms and the beta coefficients of hemodynamic responses. The group analysis of oxyhemoglobin (HbO) and total hemoglobin (HbT) levels revealed deactivation in the bilateral angular gyrus during cybersickness. In the Pearson correlation analyses, the HbO and HbT beta coefficients in the bilateral angular gyrus had a significant positive correlation with the total SSQ and disorientation. These results indicated that the angular gyrus was associated with cybersickness. These findings suggest that the hemodynamic response in the angular gyrus could be a biomarker for evaluating cybersickness symptoms.

Brain activity differences between susceptible and non-susceptible populations under visually induced motion sickness based on sensor-space and source-space analyses

The neural mechanisms underlying visually induced motion sickness (VIMS) in different susceptible populations are unclear, as it is not clear how brain activity changes in different susceptible populations during the vection section (VS). This study aimed to analyze the brain activity changes in different susceptible populations during VS. Twenty subjects were included in this study and divided into the VIMS-susceptible group (VIMSSG) and VIMS-resistant group (VIMSRG) based on a motion sickness questionnaire. 64-channel electroencephalogram (EEG) data from these subjects during VS were collected. The brain activities during VS for VIMSSG and VIMSRG were analyzed with time-frequency based sensor-space analysis and EEG source imaging based source-space analysis. Under VS, delta and theta energies were significantly increased in VIMSSG and VIMSRG, while alpha and beta energies were only significantly increased in VIMSRG. Also, the superior and middle temporal were activated in VIMSSG and VIMSRG, while lateral occipital, supramarginal gyrus, and precentral gyrus were activated only in VIMSSG. The spatiotemporal differences in brain activity observed between VIMSSG and VIMSRG may be attributed to the different susceptibility of participants in each group and the different severity of MS symptoms experienced. Long-term vestibular training can effectively improve the ability of anti-VIMS. The knowledge gained from this study helps advance understanding of the neural mechanism of VIMS in different susceptible populations.

Estimating objective (EEG) and subjective (SSQ) cybersickness in people with susceptibility to motion sickness

Cybersickness refers to the uncomfortable side effects, such as headaches, dizziness, and nausea, felt while experiencing virtual reality (VR). This study investigated cybersickness in people with sensitivity to motion sickness using electroencephalography (EEG), the Simulator Sickness Questionnaire (SSQ), and simple VR content. Based on the scores from the Motion Sickness Susceptibility Questionnaire (MSSQ), 40 males in their twenties were selected as the sensitive group (n = 20) and non-sensitive group (n = 20). The experiment contained two conditions: a baseline condition representing a resting state and a cybersickness condition in which watching VR content induced cybersickness. The SSQ score increased significantly after watching the VR content in both groups. The sensitive group showed significantly lower absolute power in the beta and gamma bands than the non-sensitive group. The cybersickness condition showed significantly increased delta and decreased alpha compared to the baseline condition. We evaluated EEG and SSQ to identify subjective symptoms and objective physiological changes associated with cybersickness.