Lack of sleep hurts handling of unexpected UNIVERSITY PARK, Pa., May 2 (UPI) -- Surgeons who are sleep-deprived can perform a learned task or learn a new task, but have trouble dealing with the unexpected, U.S. researchers say. Dr. Jonathan Tomsk, a research fellow involved in surgical resident training at the Pennsylvania State University College of Medicine, and colleagues tested two groups of medical students -- one sleep deprived and the other rested -- over two days. All study participants were shown how to use a virtual reality simulator on the first three levels of difficulty. The study subjects practiced for no more than 45 minutes a day. Researchers instructed study participants to get a full night's rest and then tested the subjects on the first three levels of the simulator. The study participants returned for a second day of testing either fully rested -- no less than 6 hours sleep -- or sleep deprived -- less than 2 hours of sleep. The study published in American Journal of Surgery demonstrated no difference in ability to perform a previously learned simulated surgical task or to learn a new simulated surgical task while moderately sleep deprived, but in order to achieve the same level of performance, sleep-deprived subjects demonstrated increased cognitive workload -- load related to the executive control of working memory -- compared to their rested counterparts.