The aim ofthis study was to exarnine physiological responses during a mental task as indices ofmental workload . Electroencepha ] ogram ( EEG ) , heart rate variabi ] ity ( HRV ) , brain haemodynamics , and blood pressure( BP ) were measured during a visual search task accompanied with short −terrn memory . When the dithculty of task became greater , the larger changes in beta − 1 power ratio ofEEG and di astolic BP were observed . Along With work execution , parasympathetic ncrvous activity

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... reased. Furthermore, beta − 1 power ratio and increase in diastolic BP showed a significant correlation . In condusion , this study suggests that beta −l power ratio ofEEG and diastolic BP are usefUl in the evaluation of mental workload as the degree of difficulty , and HRV might be effeCtive to evaluate a time change of a mental workload with accomplishment ofthe task . Keywords ' menta1 workload , workin8 memOi K visua /search task , EEG , " RV . bloodpressure