Positive correlation between drowsiness and prefrontal activation during a simulated speed-control driving task

The present study aimed to examine the relationship between drowsiness and prefrontal activation during simulated driving tasks using a wireless portable near-infrared spectroscopy device. Participants drove from start to goal along default routes with either intentional control of their driving speed (speed-control group) or not (speed-free group). Drowsiness level was assessed using a five-item Likert-type questionnaire. The behavioral data indicated longer driving time in the speed-control group than in the speed-free group, whereas no difference in the number of errors was found between the two groups. Importantly, the speed-control group showed a significant positive correlation between the drowsiness score and left prefrontal activation, whereas the speed-free group did not. The results suggest that drowsy individuals may show increased prefrontal activation as compensatory efforts to maintain the desired level of performance in tasks that require deliberate control of behaviors. Furthermore, the present study shows that near-infrared spectroscopy may provide us with a possibility to examine the state of drowsiness during daily-life operations. (c) 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins.