An individual is being monitored with an electroencephalogram (EEG) as they relax with their eyes closed and begin to fall asleep. The recording initially shows a pattern consistent with a relaxed, awake state. What specific change in the EEG recording would indicate the onset of the very first stage of sleep?

A sleep researcher observes a participant's EEG readings as they transition from a state of relaxed wakefulness into the earliest stage of sleep. Which of the following patterns would most accurately represent this transition?