Source: Exam 1 Study Guide | General Psychology, The Ohio State University
Difficulty: Intermediate | Prerequisites: Unit 2 (Neuroscience). Understanding neurotransmitters and brain structures will help with sleep stages and drug mechanisms.
Consciousness is the topic where psychology meets some of its oldest questions: what does it mean to be aware? This unit covers the practical side of that question. You will learn what happens in the brain during different states of awareness (waking, sleeping, dreaming, mind wandering), how the body's internal clock regulates sleep, what goes wrong in sleep disorders, and how psychoactive drugs alter consciousness by acting on neurotransmitter systems. If you have covered neurotransmitters and brain anatomy in Unit 2, this unit shows you what happens when those systems are disrupted.
Consciousness varies from full alertness to deep sleep to drug-altered states. Sleep cycles through distinct stages with characteristic brain wave patterns, regulated by circadian rhythms. Sleep disorders disrupt these patterns. Psychoactive drugs change consciousness by mimicking, blocking, or altering neurotransmitter activity, and repeated use can lead to tolerance, dependence, and withdrawal.
Consciousness
Your awareness of yourself and your environment at any given moment. It exists on a continuum from full alertness to deep sleep to coma.
Default mode network (DMN)
A set of brain regions that become active when you are not focused on the outside world: daydreaming, mind wandering, thinking about yourself or others. It tends to quiet down when you are engaged in a demanding task. Think of it as what your brain does when it is "idling."
Circadian rhythm
The body's internal 24-hour clock, primarily regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus. It controls the sleep-wake cycle, body temperature, hormone release, and other biological functions. Light is the main external cue (zeitgeber) that keeps it synchronised.
Brain waves
Patterns of electrical activity in the brain measured by an electroencephalogram (EEG). Different stages of consciousness produce different brain wave patterns.
NREM sleep
Non-rapid eye movement sleep. Divided into three stages (N1, N2, N3), each progressively deeper.
REM sleep
Rapid eye movement sleep. The stage associated with vivid dreaming. Brain activity resembles waking, but the body is largely paralysed (muscle atonia).
Sleep spindles
Bursts of rapid brain wave activity during Stage N2 sleep. Thought to play a role in memory consolidation.
Delta waves
Slow, high-amplitude brain waves characteristic of Stage N3 (deep sleep). The most restorative stage.
Insomnia
Difficulty falling asleep, staying asleep, or waking too early, despite having the opportunity to sleep. The most common sleep disorder.
Sleep apnoea
Repeated interruptions in breathing during sleep, leading to frequent awakenings (often without the person's awareness). Causes daytime sleepiness and is associated with cardiovascular risk.
Narcolepsy
A disorder involving sudden, uncontrollable episodes of sleep or loss of muscle tone (cataplexy) during waking hours.
Tolerance
The need for increasingly larger doses of a drug to achieve the same effect. The body adapts to the drug's presence.
Withdrawal
Physical and psychological symptoms that occur when a person stops using a drug their body has adapted to. Symptoms are often the opposite of the drug's effects.
Addiction (substance use disorder)
Compulsive drug seeking and use despite negative consequences. Involves changes in the brain's reward circuitry, particularly dopamine pathways.
Craving
An intense desire or urge to use a substance, often triggered by environmental cues associated with past use.
Stimulants
Drugs that speed up neural activity and body functions. Examples: caffeine, nicotine, cocaine, amphetamines. They increase alertness, energy, and heart rate.
Depressants
Drugs that slow down neural activity. Examples: alcohol, barbiturates, benzodiazepines. They reduce inhibitions, slow reaction time, and impair judgement.
Opioids
Drugs that reduce pain and produce euphoria by binding to the brain's natural opioid receptors. Examples: morphine, heroin, oxycodone. Highly addictive and dangerous in overdose because they suppress breathing.
Hallucinogens
Drugs that distort perception and produce sensory experiences without external stimuli. Examples: LSD, psilocybin, mescaline. They primarily affect serotonin pathways.
Consciousness is not an on/off switch. It ranges from focused alertness through daydreaming, drowsiness, sleep, and coma.
The default mode network is a group of brain regions (medial prefrontal cortex, posterior cingulate, and others) that activate during rest and mind wandering. When you are doing a focused task, the DMN quiets down. When your mind drifts, the DMN picks up.
The DMN is thought to be involved in self-referential thought, planning, and creative thinking. Excessive DMN activity has been linked to rumination and depression.
A full sleep cycle takes roughly 90 minutes and moves through the following stages:
Awake / alert: beta waves (fast, low amplitude).
Relaxed / drowsy: alpha waves (slower, more regular).
Stage N1 (light sleep): theta waves. Lasts a few minutes. You are easily awakened. May experience hypnagogic hallucinations (brief dream-like images).
Stage N2: theta waves with sleep spindles and K-complexes. This is where you spend most of your sleep time. Thought to be important for memory consolidation.
Stage N3 (deep sleep / slow-wave sleep): delta waves (slowest, highest amplitude). The most physically restorative stage. Hardest to wake someone from. Night terrors and sleepwalking tend to occur here.
REM sleep: brain waves resemble waking (fast, irregular). Vivid dreaming occurs. Eyes move rapidly. The body is paralysed (muscle atonia) to prevent you from acting out dreams. Important for emotional processing and memory.
As the night progresses, you spend less time in deep sleep (N3) and more time in REM. Early sleep cycles are dominated by deep sleep; later cycles are dominated by REM.
The suprachiasmatic nucleus (SCN) in the hypothalamus is the master clock.
Light detected by the retina signals the SCN to suppress melatonin production (keeping you awake). Darkness triggers melatonin release (making you sleepy).
Disruptions to circadian rhythms (jet lag, shift work, irregular sleep schedules) impair cognition, mood, and physical health.
Teenagers experience a natural shift in their circadian rhythm that pushes sleep onset later, which is why early school start times are a problem.
Insomnia: the most common. Difficulty initiating or maintaining sleep. Can be acute (short-term, triggered by stress) or chronic.
Sleep apnoea: breathing repeatedly stops during sleep. The person often does not realise it. Treated with CPAP machines. Associated with obesity and cardiovascular disease.
Narcolepsy: sudden, uncontrollable sleep episodes during the day, sometimes accompanied by cataplexy (sudden loss of muscle tone triggered by strong emotion).
Sleepwalking (somnambulism): occurs during deep sleep (N3), not during REM. The person has no memory of the episode.
REM sleep behaviour disorder: the normal paralysis during REM fails, and the person physically acts out their dreams.
Tolerance: the body adapts to the drug, so more is needed for the same effect. This is a physiological change, not a choice.
Withdrawal: when the drug is removed, the body reacts, often with symptoms opposite to the drug's effects (e.g. a stimulant user may experience fatigue and depression).
Craving: a powerful urge to use, often triggered by environmental cues (a place, a person, a situation associated with past use). Cravings can persist long after withdrawal is over.
Addiction involves compulsive use despite harm. The brain's dopamine reward system is central: drugs hijack this system, producing far more dopamine than natural rewards do, which reinforces the drug-seeking behaviour.
Stimulants (caffeine, nicotine, cocaine, methamphetamine, MDMA): increase neural firing, raise heart rate and alertness. Cocaine and methamphetamine block dopamine reuptake, flooding the synapse.
Depressants (alcohol, barbiturates, benzodiazepines): slow neural activity by enhancing GABA (an inhibitory neurotransmitter). Impair judgement, slow reflexes. High doses can be fatal because they suppress breathing.
Opioids (morphine, heroin, fentanyl, oxycodone): bind to endorphin receptors, reducing pain and producing euphoria. Extremely addictive. Overdose risk is high because they suppress respiration.
Hallucinogens (LSD, psilocybin, mescaline): distort perception, thought, and mood. Primarily act on serotonin receptors. Effects are unpredictable and highly influenced by set (mindset) and setting (environment).
Cannabis (marijuana): has properties of multiple drug classes. THC binds to cannabinoid receptors. Effects include altered perception, impaired short-term memory, and relaxation. Classified separately in many textbooks.
Students often think we dream only during REM sleep. While the most vivid and story-like dreams occur during REM, some dreaming also happens during NREM stages.
Students confuse sleepwalking with REM. Sleepwalking occurs during deep NREM sleep (Stage N3), not during REM. During REM, the body is paralysed.
Students sometimes think tolerance means the drug has stopped working. The drug still works; the body has adapted so that the same dose produces a weaker effect. The pharmacology has not changed; the body's response has.
Students often treat "physical dependence" and "addiction" as the same thing. A person can be physically dependent (experiencing tolerance and withdrawal) without meeting the criteria for addiction, which includes compulsive use despite harm.
⚠️ Know all the sleep stages in order, including the type of brain wave associated with each.
⚠️ Be able to explain what the default mode network does and when it is active vs. quiet.
⚠️ Understand circadian rhythms, the role of the SCN, and how light/melatonin interact.
⚠️ Be able to distinguish the major sleep disorders (insomnia, sleep apnoea, narcolepsy) and which sleep stage each is associated with.
⚠️ Know the four drug classes and at least one example and one mechanism of action for each.
⚠️ Understand the relationship between tolerance, withdrawal, craving, and addiction.
The brain network associated with daydreaming and mind wandering is called the __________.
True or False: Delta waves are associated with light sleep (Stage N1).
The body's master circadian clock is located in the __________.
True or False: Sleepwalking occurs during REM sleep.
A drug that slows neural activity and enhances GABA is classified as a __________.
Q: Describe how a typical night of sleep changes from the first cycle to the last.
A: Early cycles contain more deep sleep (Stage N3, delta waves). As the night goes on, N3 periods shorten and REM periods lengthen. By the final cycle, most of the time is spent in REM sleep.
Q: A shift worker reports difficulty concentrating, irritability, and trouble sleeping during the day. What is the most likely explanation?
A: Disruption of circadian rhythms. Their internal clock (regulated by the SCN) is out of sync with their work schedule. Light exposure at night suppresses melatonin, and trying to sleep during the day conflicts with the body's natural alertness cycle.
Q: How does cocaine produce its effects at the level of the synapse?
A: Cocaine blocks the reuptake of dopamine. This causes dopamine to accumulate in the synapse, intensely stimulating the receiving neuron and producing feelings of euphoria and energy.
Q: Explain why withdrawal symptoms are often the opposite of a drug's effects.
A: During repeated use, the body adapts to counteract the drug's effects (tolerance). When the drug is removed, those compensatory responses are unmasked. For a depressant, the body had increased excitatory activity to compensate; without the drug, that excess excitation produces anxiety, tremors, and insomnia.
Q: What is the difference between the default mode network being active and being in Stage N1 sleep?
A: The DMN is active during waking rest and mind wandering, when you are still conscious but not focused on a task. Stage N1 is the onset of sleep: consciousness is fading, brain waves shift to theta, and you may experience hypnagogic hallucinations. Both involve reduced external focus, but N1 is a sleep state while DMN activity occurs during wakefulness.
This unit ties back to Unit 2 (Neuroscience) throughout: sleep stages are defined by patterns of neural electrical activity, drug mechanisms operate on the same neurotransmitter systems (dopamine, serotonin, GABA) you learnt there, and the circadian clock sits in the hypothalamus. It also connects to Unit 3 (Sensation and Perception), since drugs like hallucinogens distort perceptual processing, and sensory input (light) is the primary regulator of circadian rhythms.
Consciousness, altered states, default mode network, DMN, mind wandering, sleep stages, NREM, REM, N1, N2, N3, alpha waves, beta waves, theta waves, delta waves, sleep spindles, K-complex, circadian rhythm, suprachiasmatic nucleus, SCN, melatonin, jet lag, insomnia, sleep apnoea, sleep apnea, narcolepsy, cataplexy, sleepwalking, somnambulism, tolerance, withdrawal, addiction, substance use disorder, craving, dopamine, stimulants, depressants, opioids, hallucinogens, cannabis, GABA, serotonin, cocaine, alcohol, PSYCH 1100, general psychology, Ohio State