Fetal Sleep Patterns

We can  study the  activity of  different parts of the brain by placing electrodes on the fetal sheep brain and the muscles they control.  The electrocorticogram (ECoG)  records brain activity. The electrooculogram  (EOG) records eye movements. The neck muscle electromyogram records  the activity of the  muscles that  hold  up  the head. Neck  muscle activity stops when we  sleep. That is why if we fall asleep when sitting, the neck muscles stop  contracting and our heads flop forward.  

Records like this  show that the fetus undergoes bouts of sleep and wakefulness. Rapid eye movements (REM) occur during some of the time the fetus is sleeping.  This pattern of sleep is similar to REM sleep seen when adults dream.