Abstract
A new method is proposed for monitoring the arousal level by detecting the grouping of blinks. An experiment of monotonous auditory task was performed where the subject was instructed to recognize the Morse-code for a period of 30 to 40 minutes. Blinking was recorded by using capacito-oculography (COG) developed by the authors together with EEG and task performance. In COG measurement the subject wears goggles having translucent metal electrodes for detecting a capacitance change due to blinking. Frequency modulated UHF signals are transmitted wirelessly from an oscillator mounted on the goggles. The blink grouping is defined as more than two successive blinks at the interval of less than 1 second. The blink grouping reached the maximum rate 10 to 25 minutes after the onset of the experimental session when the alpha index of EEG increased up to two to three times the initial level and the rate of missed signals began to increase rapidly. When the arousal level decreased further, the rate of blink grouping returned to a low level again. Therefore, the blink grouping may be used effectively as basic information to provide the operator with a warning signal to avoid hazards due to a lowered arousal level.
