The new definition of sleep

Here's a really interesting article about sleep I found on Plime just now. This paragraph in particular would explain why I'm prone to confusion and bad memory, particularly when I've had less sleep, I seem to be one of those unfortunate 60% people without a "back-up system":

Brain imaging has recently revealed a mental back-up system in people who remain alert when sleep-deprived (Journal of Neuroscience, vol 29, p 7948). While other people have reduced brain activity when tired, sleep-resistant individuals manage to maintain their brain activity levels. More interestingly, they also recruit new areas to help compensate for having been awake for so long. These people were selected for the study because they had a gene variant found in around 40 per cent of people that is thought to be associated with resistance to sleep deprivation. It seems likely that such people are also less prone to state dissociation, although this has not yet been tested.