Electroencephalographic study of mental fatigue in visual display terminal tasks

In this study, an attempt was made to evaluate mental fatigue induced during a visual display terminal (VDT) task using electroencephalography (EEG) power indices and P300 component of event-related potential (ERP). The VDT tasks were performed after 60 min of mental arithmetic and 120 min of data entry via computer. Three measurement sessions including before (BT), immediately after (AT), and 60 min after (60-min AT) tasks were undertaken in the present study. The EEG measures were conducted and the ERPs induced from a modified Flanker task were acquired on twenty subjects during the three test sessions. Behavior response and EEG measurement were recorded on a personal computer. For EEG power, three basic indices and three ratio indices were calculated from preprocessed EEG signals. Indices of EEG power of α, θ, θ/α and (α+θ)/β showed significant differences between AT and BT. After the experimental task, the amplitude significantly decreased and latency of P300 significantly increased. The results indicated the subjects appeared predominantly mental fatigue after three hours of VDT task. After 60 min of rest, the participants' fatigue did not diminish to original state except in the visual area. The method proposed in this study is potentially applicable to evaluate the fatigued state of workers and to manage the mental fatigue from the viewpoints of occupational risk management, productivity, and occupational health.