A sleep lab technician is monitoring a research participant who is in a deep, non-dreaming state of sleep. The participant's heart rate and respiration are slow and steady. When the technician tries to wake the participant by calling their name, the participant does not respond. An electroencephalogram (EEG) is recording the participant's brain activity. Which of the following descriptions best characterizes the brain waves the technician is most likely observing?

A sleep researcher is monitoring a participant's brain activity using an electroencephalogram (EEG). The researcher notes that the participant is very difficult to awaken and is likely in the deepest stage of non-rapid eye movement (NREM) sleep. Which of the following EEG patterns would the researcher most likely be observing?