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Slow Eye Movement as a Biological Marker of Drowsy Driving
Published October 12, 2011 by Society of Automotive Engineers of Japan in Japan
Recently, we have demonstrated deteriorated hazard-avoidance performance in a drowsy state, associated with reduced baseline activity in the brain stem reticular formation, using functional magnetic resonance imaging. This result suggests that biological markers of drowsy driving are required to reflect the brain stem reticular formation activity. The brain stem reticular formation contains the raphe nuclei, which plays a critical role in the fixation of gaze. It is shown that when neurons in the raphe nuclei are inhibited in a drowsy state, gaze fixation is no longer maintained, and consequently, slow oscillatory eye movement emerges. This evidence indicates that a distinct eye movement pattern, termed slow eye movement (SEM), satisfies a requirement for a biological marker of drowsy driving. Thus, the present study aims to examine an elemental performance for hazard-avoidance (reaction time to a visual target) in the presence of SEM. In a long-lasting simple detection task of a visual target, horizontal eye movement was recorded using an electrooculogram, and the absence or presence of SEM was determined at the onset of each stimulus on the basis of the consensus of three human raters. As a result, we found that reaction time in the presence of SEM was significantly longer than reaction time in the absence of SEM, and that the prediction accuracy of SEM for excessive reaction delay (over 1 s) was fairly good in a laboratory setup. These results suggest that SEM can be a useful biological marker of drowsy driving.