Blink reflex as a parameter of human operator's functional state

Eyelid movements (EM)--blinking frequency and duration of closed eyes--may serve as a parameter of fatigue in humans performing as operators. Twenty subjects were told to locate and follow visual signals appearing on a screen at the frequency of 4-5 X h-1 and moving in a background of bright noises. EM was recorded in infra-red rays with tiny sensors attached to glasses' rim. EEG and ECG were recorded simultaneously. It was found that a change in EM is a sensitive parameter of fatigue and better corresponds to decreased quality of performance (time of locating signal and error in following), than changes in R-R interval. In the second experimental series, symptoms of fatigue discovered by EM were accompanied by sound signals, which improved operator's performance by 15-20%. Recording of EM may be used to monitor operator's state in humans and to forecast reliability of performance.