clipped from: www.scientificamerican.com   

Why we dream continues to elude us. Scientists have proven we need to dream. When robbed of their dreams, rats die within four weeks.

We also know that at seven months a fetus is dreaming, its muscles and eye movements giving the tell-tale signs of REM (or rapid eye movement) sleep and non-REM sleep. But what happens before seven months? When do our dreams begin?

Research published in Chaos, a journal of The American Institute of Physics, provides the first attempt at an answer.

Mathematicians analyzed the brainwaves of a fetal sheep in utero, at 15-weeks.
But using sophisticated mathematics, scientists discerned a pattern of cortical activation and deactivation, cycling every five to ten minutes — this, the scientists note, is a crude precursor to the longer cycles of REM and non-REM sleep.
the study shows that dreamlike sleep develops before rapid eye movements. And the discovery may give researchers new insight into the purpose of sleep and dreams.