Neurogenesis During Sleep?

A team from Princeton University recently tested whether it is a lack of sleep that stops neurogenesis in the brain, or merely the stress as a result from the sleep deprivation. The rats were kept awake for 72 hours and cortisol measurements were recorded to assess the stress level of the rats. A second group of rats with adrenal glands removed were then subjected to the same experiment and artificially supplied with normal amounts of cortisol. These rats were tested for neurogenesis activity and found that those with normal amounts of cortisol, despite the amount of sleep deprivation, still maintained normal amounts of neurogenesis. This supports the conclusion that it is the stress that causes a disruption in neurogenesis, not the sleep itself.
This interests me because I am intensely interested in polyphasic sleep which subjects the human body to a temporary sleep deprivation state in order to change normal REM cycles to a more disperse pattern. It is important to know the exact benefits and consequences of this lifestyle before attempting it for an extended period.