MCAT Sleep and Consciousness Practice Questions: Stages, Rhythms and Dreams

Answer: C. Segment 3

Segment 3 shows delta-dominated slow-wave sleep (N3), the stage from which sleepwalking and night terrors usually arise. Segment 4 is REM, and during REM the near paralysis of skeletal muscles normally prevents walking. Segment 2 is N2, marked by spindles and K complexes, and segment 1 is relaxed wakefulness.

Answer: B. 21 percent

Total REM is 10 + 20 + 30 + 40 = 100 minutes, and 100/480 = 0.208, about 21 percent. The table also shows the typical pattern, with N3 front-loaded early in the night and REM periods growing later. The 33 percent and 50 percent choices would require far more REM than the table lists.

Answer: A. Suppress melatonin release from the pineal gland and tend to delay sleep onset

Retinal cells signal light to the suprachiasmatic nucleus, which in turn reduces melatonin release from the pineal gland. Light late in the evening suppresses melatonin and shifts the clock later, delaying sleep onset. Melatonin rises in darkness, not light, so choice B is reversed, and evening light delays the clock rather than advancing it (D).

Answer: D. Narcolepsy

Excessive daytime sleepiness, cataplexy triggered by emotion, hypnagogic hallucinations and REM onset soon after falling asleep are hallmarks of narcolepsy, often linked to loss of orexin (hypocretin) neurons in the hypothalamus. Insomnia is trouble falling or staying asleep, somnambulism is sleepwalking from N3, and apnea causes sleepiness through repeated breathing interruptions.

Answer: C. Loss of the normal muscle atonia of REM sleep

Acting out a vivid, recalled dream points to REM sleep behavior disorder, in which the brainstem mechanism that normally paralyzes skeletal muscles during REM fails. Night terrors arise from N3 and usually leave little dream recall, and sleepwalking also comes from N3. Narcolepsy involves cataplexy while awake, not acting out dreams.

Answer: D. Activation-synthesis theory

Activation-synthesis theory holds that brainstem activity during REM is random and that the cortex synthesizes it into a dream narrative after the fact. Freud saw dreams as disguised wishes with hidden latent content, information-processing theory links dreams to sorting and consolidating the day's memories, and neurocognitive theory ties dreams to waking cognition and brain development.

Answer: B. Social-cognitive (role) theory

The social-cognitive, or role, theory treats hypnotic behavior as people fulfilling the social role of a hypnotized subject. Dissociation theory instead says hypnosis splits consciousness into separate streams, as in the hidden observer idea. Activation-synthesis is a theory of dreaming, and psychoanalytic theory concerns unconscious conflict, not hypnosis.

Answer: A. An EEG dominated by high-amplitude delta waves

High-amplitude delta waves define N3, slow-wave sleep, not REM. During REM the EEG is fast and low in amplitude, much like an awake brain, while skeletal muscles are nearly paralyzed and the most vivid, narrative dreams occur. That mismatch between an active brain and an inactive body is why REM is called paradoxical sleep.

Answer: D. Alpha and theta activity increase

Meditation is a relaxed but awake state, and it is most often associated with more alpha and theta activity than alert waking. Spindles and K complexes mark N2 sleep, and dominant delta waves mark N3, so those would mean the person had fallen asleep. Beta activity is typical of alert, focused waking, not relaxation.

Answer: C. Obstructive sleep apnea

Continued breathing effort without airflow means the airway is physically blocked, which defines obstructive sleep apnea; loud snoring fits a narrowed upper airway. In central sleep apnea the brainstem stops sending the signal to breathe, so breathing effort pauses too. Narcolepsy and REM sleep behavior disorder do not cause these airflow pauses.