Topographic EEG study of visual display terminal (VDT) performance with special reference to frontal midline theta waves.

Operators of visual display terminals (VDT) often complain of physical, as well as psychological stress. Under certain circumstances, increased psychological stress among VDT operators is seen to create serious problems in their occupations, yet few studies have dealt directly with this problem. It is not clear how this should be measured and evaluated. We report the results of experiments where psychological stress was induced during VDT tasks such as visual search and computer mouse operations. The relationship between spatio-temporal analysis of EEG activity and productivity of VDT work was investigated. The subjects were divided into three age groups: young adults (18-22 years old), middle-aged (38-42 years old) and the elderly (58 years and over). Characteristic EEG changes occurred during VDT tasks. These consisted of frontal midline theta waves with maximum amplitude at Fz. Statistically significant relationships were found between duration of working, EEG electrode location on the head, as well as correlations between work speed and variation of theta waves. It was concluded that some factors relating to the severity of a mental task and the distribution of cortical EEG potentials are closely related. When long lasting theta waves appear in the EEG, a rest period should be considered, before the subjects complain of fatigue. An effective method to optimally determine the duration of work and rest periods can be designed using the EEG.