Clin Exp Otorhinolaryngol.  2019 Nov;12(4):376-384. 10.21053/ceo.2018.01592.

Feasibility of Eye Tracking Assisted Vestibular Rehabilitation Strategy Using Immersive Virtual Reality

• Park JH
• Jeon HJ
• Lim EC
• Koo JW
• Lee HJ
• Kim HJ
• Lee JS
• Song CG
• Hong SK

• KMID: 2462733
• DOI: http://doi.org/10.21053/ceo.2018.01592

Abstract

OBJECTIVES
Even though vestibular rehabilitation therapy (VRT) using head-mounted display (HMD) has been highlighted recently as a popular virtual reality platform, we should consider that HMD itself do not provide interactive environment for VRT. This study aimed to test the feasibility of interactive components using eye tracking assisted strategy through neurophysiologic evidence.
METHODS
HMD implemented with an infrared-based eye tracker was used to generate a virtual environment for VRT. Eighteen healthy subjects participated in our experiment, wherein they performed a saccadic eye exercise (SEE) under two conditions of feedback-on (F-on, visualization of eye position) and feedback-off (F-off, non-visualization of eye position). Eye position was continuously monitored in real time on those two conditions, but this information was not provided to the participants. Electroencephalogram recordings were used to estimate neural dynamics and attention during SEE, in which only valid trials (correct responses) were included in electroencephalogram analysis.
RESULTS
SEE accuracy was higher in the F-on than F-off condition (P=0.039). The power spectral density of beta band was higher in the F-on condition on the frontal (P=0.047), central (P=0.042), and occipital areas (P=0.045). Beta-event-related desynchronization was significantly more pronounced in the F-on (-0.19 on frontal and -0.22 on central clusters) than in the F-off condition (0.23 on frontal and 0.05 on central) on preparatory phase (P=0.005 for frontal and P=0.024 for central). In addition, more abundant functional connectivity was revealed under the F-on condition.
CONCLUSION
Considering substantial gain may come from goal directed attention and activation of brain-network while performing VRT, our preclinical study from SEE suggests that eye tracking algorithms may work efficiently in vestibular rehabilitation using HMD.

Keyword

Virtual Reality; Vestibular Diseases; Rehabilitation; Electroencephalography

MeSH Terms

Electroencephalography
Healthy Volunteers
Rehabilitation*
Vestibular Diseases

Figure

• 

  Fig. 1. Saccadic eye exercise condition under a head-mounted display and the experimental paradigm. Participants were instructed to move their eyes quickly from target to target presented at 1.25-second intervals in the virtual space and to then fix their eyes on a fixation point for 1.5 seconds. In experiment A (feedback-on [F-on] condition), participants were provided with information regarding eye position in real time (a small white circle) and feedback by changes in the visual target (from black to red) when the gaze fell on the designated visual target. Conversely, no feedback function was provided in experiment B (feedback-off [F-off] condition). Real-time eye position was continuously recorded in both conditions, but this information was not provided to the participants.

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  Fig. 2. Accuracy of saccadic exercise. The accuracy was 81.82%±14.13% in the feedback-on (F-on) condition and 65.71%±24.32% in the feedback-off (F-off) condition, which showed a significant difference. *P=0.039.

• 

  Fig. 3. Mean power spectral density (PSD) at the frontal (A), central, (B) parietal (C), and occipital (D) channel clusters. The asterisk in the thick rectangular space represents a statistically significant difference (P<0.05) between the feedback-off (F-off) and feedback-on (F-on) conditions in the given frequency bands; theta (4–7 Hz), alpha (8–12 Hz), and beta (13–30 Hz). The bottom panel in each cluster indicates a comparison of PSD between F-off versus F-on conditions in the given beta frequency range. The beta band-PSD in the frontal area, central area and occipital area were significantly higher in the F-on condition than in the F-off condition (*statistically significant differences, P=0.047 for frontal, P=0.042 for central and P=0.045 for occipital area). The error bars in each figure for PSD represent standard error of the mean from given frequency band datasets.

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  Fig. 4. Event-related spectral perturbation (ERSP) at the frontal (A) and central (B) channel clusters. ERSP was calculated on a prestimulation time window as −1,000 ms before the onset of target presentation (dash line) at the frontal (A) and central (B). The power level is coded on a color scale in decibels, in which synchronization appears red while desynchronization appears blue on the ERSP plots. The ERSP revealed larger beta-ERD in the feedback-on (F-on) than in the feedback-off (F-off) condition, in which mean beta-ERDs during preparatory period from –750 to –500 ms were calculated to be −0.19 on frontal and −0.22 on central area in F-on condition, whereas event-related power modulations during the same time period showed ERS (0.231 on frontal and 0.05 on central) rather than ERD pattern in F-off condition, which was statistically significant (*P=0.005 for frontal and P=0.024 for central). ERS, event-related synchronization; ERD, event-related desynchronization.

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  Fig. 5. Dynamic mean functional connectivity across four bilateral visual-vestibular multisensory processing-related brain regions. Functional connectivity is shown for the theta band for the saccadic period (A, B), and the gamma band for the fixation period, respectively (C, D). Scale bar represents the coefficient value using statistical assessment of surrogates (1,000 surrogate data sets, P<0.05). During the saccadic exercise period, more abundant dynamic connectivity in the theta band across the frontal eye field (FEF), primary somatosensory cortex (S1), parieto-insular vestibular cortex (PIVC) and primary visual cortex (V1) areas in the feedback-on (F-on) condition than in the feedback-off (F-off) condition was observed. In the fixation period, those from the right PIVC to the contralateral PIVC and both V1s, as well as between both S1s were observed under the F-on condition. However, no dynamic functional connectivities besides those between both PIVCs were observed under the F-off condition.

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