Fig. 4. Probe response time as a function of case elapsed time for one subject in both conditions (sleep-deprived condition =•; sleep-extended condition =○. Each symbol shape denotes one of the three types of probes. The vertical scale is broken to show extreme values. The long response latency at 15 min elapsed time occurred during anesthetic induction. Missed probes at 160 and 215 min elapsed time occurred while the subject was asleep.