Sleep deprivation affects the brain in ways that can be detected through imaging. Lack of sleep alters the brain's metabolism; it produces less growth hormone. Some parts of the brain become much less active as your sleep debt grows, while others become busier as they attempt to compensate.
For instance, the temporal lobe -- which assists in language processing -- becomes less active the longer you stay awake, while a related area -- the parietal region -- partially makes up for the slack by becoming more active [source: UC San Diego Health System].
One study showed sleep-deprived subjects exhibited diminished activity in the regions of the brain that handle mathematics. No other region stepped up to help, so participants did much worse when doing mathematics on little sleep.
Without sleep, you also have slower reaction times and more difficulty with fine motor skills, which are controlled by the brain's motor cortex in the rear of the frontal lobe. And you become more impulsive and less inhibited [source: Anderson]. Combined with all the other detrimental effects of sleep deprivation, diminished ability to make good decisions can lead to lots of trouble.
Nobody knows this better than casinos, which benefit most when you're not thinking clearly. Casinos use several tricks to reduce your awareness of the passing of time and keep you on the floor, surrounded by opportunities to lose money. There are no clocks or windows in most casinos, and it's hard to find an exit.
One of the cognitive difficulties we encounter with sleep deprivation is an inability to assess our cognitive difficulties. The sleep-deprived just can't recognize the effects of sleep deprivation. So the likelihood of making risky decisions increases. This situation is especially dangerous in professions that offer little margin for error, such as law enforcement, heavy industry, health care or fire and rescue.
Compared with those who get seven or eight hours of sleep per night for a week, those who sleep only five hours a night make riskier decisions, pay less attention to negative consequences and focus more on short-term gains [source: Stevens]. While normally we approach risk in a defensive manner -- guarding against losses -- sleep deprivation makes us more likely to go for the gains confidently and disregard other consequences. In other words, we're more likely to place a large bet at the roulette table and let it ride.
Read on for lots more information about sleep deprivation that may keep you up.