"Perhaps most fascinating [about sleep loss], the emotional context of memory affects where it gets processed. Negative stimuli get processed by the amygdala; positive or neutral memories get processed by the hippocampus. Sleep deprivation hits the hippocampus harder than the amygdala. The result is that sleep-deprived people fail to recall pleasant memories, yet recall gloomy memories just fine."
So, if you need another reason to go to bed earlier, there you go. Now get some sleep already!! (Says the mother of four small children, two of whom wake up at least three times a night. . .)