Sleep deprivation systematically changes eye movement characteristics

During our day-to-day life, sleepiness endangers the safety of us as well as of others. Specifically, it impairs operator performance in security-related working environments, for example in aviation. To reduce the number and impact of sleepiness-related accidents, easy to handle monitoring methods are needed. Here, we investigate the relationship between gaze as a measure of visual attention and sleepiness. After two days and two nights of adaptation in the sleep laboratory, we randomly assigned subjects to the treatment group with 24 hours of sleep deprivation. Control subjects were allowed to sleep normally. The day before and the day after the treatment night we measured their eye movements during free viewing of natural images. The results indicated a decrease of visual exploration behavior for sleep-deprived subjects, mirrored by a reduction in the entropy of the spatial distribution of fixation locations. Likewise, sleep deprivation led to shorter saccade amplitudes. On the other hand, we did not find significant effects on the number of fixations. In contrast to control subjects, the median single fixation duration decreased in sleep-deprived subjects. Overall, our findings suggested that sleep deprivation leads to systematic changes in eye movement characteristics that can be distinguished from normal viewing behavior