AElectroencephalogram (EEG) activity is increased, with the appearance of spikes called K complexes.
BElectroencephalogram records delta activity.
CEye movement ceases, wave frequency is reduced, and wave amplitude is increased.
DEye movements are slow and electroencephalogram (EEG) shows low brain wave activity.
EDeep sleep occurs.
✓ Correct answer: D. Eye movements are slow and electroencephalogram (EEG) shows low brain wave activity.The non-rapid eye movement stage of sleep, NREM or synchronized sleep, involves four stages. The transition from wakefulness to sleep occurs during stage 1. Eye movements are slow and the electroencepalogram (EEG) shows low brain wave activity. In stage 2, EEG activity is increased. Spikes called K complexes are recorded. In stage 3, eye movement ceases. Wave frequency is reduced and amplitude is increased. Delta activity is recorded on the EEG in stage 4. Stages 3 and 4 are considered deep sleep.
Keep practising. Use the free MCAT PDF, watch the YouTube walkthrough, or unlock all 10 web questions with timed mock exams.
Free practice here. Timed mocks when you are ready.
Study the MCAT Exam Prep 2026 Test free question explanations, download the PDF, then unlock timed mock exams on the web when you want exam-day practice.
Theory