[Below is the original script. But a few changes may have been made during the recording of this audio podcast.]

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. The brain signals at that stage are quite complex, set against noise that is difficult to dampen. 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.

We can only guess at the content—do sheep dream of electric androids?  But 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.

—Christie Nicholson