Abstract
EEG is widely used in cognitive and behavioral research. This study evaluates the effectiveness of using the EEG power and mean amplitude indices to measure visual fatigue and mental workload. Two-stage experiments are included in this study. In the first experiment, three common visual fatigue measures, critical-flicker fusion (CFF), near-point accommodation (NPA) and subjective eye-fatigue rating (questionnaire) were used to compare with the EEG power index. The subjects were 20 men with a mean age of 20.4 years (SD=1.46). The experimental task was a 120 min car-racing video game. Results indicated that the EEG power indices were valid as a visual fatigue measure and the sensitivity was higher than the subjective measure. The EEG β and EEG α power indices were effective for measuring visual fatigue in short and long-duration tasks, respectively. The EEG β/α was the most effective power index for the visual fatigue measure in this experiment. The second experiment aimed to identify EEG mean amplitude indices that can accurately monitor mental workload while subjects performed multiple tasks with the strategy of maintaining stable performance and maximizing accuracy. 30 male subjects completed three 10 min multitasks with 3 workload levels. 25 mental workload measures including 10 EEG mean amplitude indices (α, β, θ, α/θ, θ/β from O1-O2 and F4-C4), heart rate, 12 heart rate variability (HRV) indices, and 2 subjective measures data were collected. One-way ANOVA with repeated measures, Pearson correlation and Duncan post-hoc test were employed to observe index sensitivity. The results showed that EEG θ, α/θ (F4-C4), and SDNN, VLF, LF, %HF, LF/HF are sensitive to differentiated high workload levels. EEG α/θ (F4-C4) and LF/HF are most effective for monitoring high mental workload. EEG α/θ (F4-C4) showed strong correlations with subjective measures across different mental workload levels. Additionally, we found the operation strategy would affect the sensitivity of EEG α (F4-C4) and HF. These findings identified the EEG measure are valid in measuring visual fatigue and mental workload. Besides, the task characteristic and operation strategy might affect the validity of EEG indices. The results, furthermore, can be applied to enhance the safety, health, and comfort of the users involved in heavy visual requirement and mental workload tasks.Keywords: EEG, visual fatigue, mental workload, physiological index, subjective rating.