A 7-year-old girl is brought to the pediatric neurology clinic with a 6-month history of frequent brief episodes of staring and unresponsiveness lasting 10–15 seconds, occurring multiple times daily. Teachers report she appears to "daydream" in class. An EEG is performed, and the feature marked **D** in the diagram is observed during the diagnostic test. Which of the following best explains why this finding is considered a high-yield diagnostic maneuver in childhood absence epilepsy?