Dependent variables included the CFF values, EEG relative power indices, and SSQ scores. In this study, the CFF value and EEG relative power indices were used to measure the severity of visual fatigue and recovery from visual fatigue. CFF values were collected for both eyes, and the mean value of three ascending trials (flicker-to-fusion trial) and three descending trials (fusion-to-flicker trial) was used as the CFF value [13 (link)].
After completing the visual tasks and during rest, EEG signals were measured. EEG Ag/AgCl electrodes were attached to specific locations on each participant’s scalp. The exploring electrodes were located over the left occipital lobe (O1) and right occipital lobe (O2); the reference electrodes were located on the prominent bone just behind the left ear (A1) and that just behind the right ear (A2). The electrode locations were based on the international 10–20 system [16 ]. EEG signals were monitored at 1024 Hz, and raw data were processed using the BioTrace+ software with an IIR bandpass filter. Prior to data processing, a 60 Hz notch filter was applied to remove environmental artifacts [15 (link)]. With respect to the EEG signals, relative power indices, α, β, θ, θ/α, and β/α, were used as dependent variables for subsequent analyses.
The SSQ scores, comprising 16 symptoms that reflect the severity of visually induced motion sickness (VIMS), were used in this study to measure VIMS severity and recovery. Participants rated each SSQ item on a 4-point Likert scale (0 = not at all, 1 = slight, 2 = moderate, 3 = severe) [22 (link)]. Kennedy et al. [22 (link)] indicated that the total severity score is obtained by adding each SSQ item scale multiplied by the weighted score of nausea, oculomotor symptoms, and disorientation, as presented inTable 1 .
After completing the visual tasks and during rest, EEG signals were measured. EEG Ag/AgCl electrodes were attached to specific locations on each participant’s scalp. The exploring electrodes were located over the left occipital lobe (O1) and right occipital lobe (O2); the reference electrodes were located on the prominent bone just behind the left ear (A1) and that just behind the right ear (A2). The electrode locations were based on the international 10–20 system [16 ]. EEG signals were monitored at 1024 Hz, and raw data were processed using the BioTrace+ software with an IIR bandpass filter. Prior to data processing, a 60 Hz notch filter was applied to remove environmental artifacts [15 (link)]. With respect to the EEG signals, relative power indices, α, β, θ, θ/α, and β/α, were used as dependent variables for subsequent analyses.
The SSQ scores, comprising 16 symptoms that reflect the severity of visually induced motion sickness (VIMS), were used in this study to measure VIMS severity and recovery. Participants rated each SSQ item on a 4-point Likert scale (0 = not at all, 1 = slight, 2 = moderate, 3 = severe) [22 (link)]. Kennedy et al. [22 (link)] indicated that the total severity score is obtained by adding each SSQ item scale multiplied by the weighted score of nausea, oculomotor symptoms, and disorientation, as presented in
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