Consciousness & Sleep

This is Unit Three of Psychology: consciousness and sleep. The unit opens on a clock. Not a metaphorical one — an actual structure in the hypothalamus keeping a cycle of roughly twenty-four hours, running whether or not anybody is watching a clock face. Most of what goes wrong with sleep is a mismatch with that cycle, and the unit covers two of them directly. Crossing time zones. And shift work, which forces the same mismatch repeatedly rather than once. Then the architecture of a night — four stages, three of them progressively deeper and one that is not deeper at all, though almost everybody assumes it is. The error entry there is precise about why: depth is measured by how hard someone is to wake, and it has nothing to do with how rich the experience was. The last third covers substances. This part of the unit is definitional throughout — five classes, named by what they do to nervous system activity, and three terms for what repeated use produces. By the end you will be able to do five things. One: say what sets the sleep-wake cycle and what pushes it out of alignment. Two: say why REM is not the deepest stage. Three: state what each theory of sleep's function claims. Four: say what separates physical from psychological dependence. Five: say what separates a night terror from a nightmare.

Four entries establishing the cycle. Consciousness is not on or off — it varies continuously across a day, and what governs that variation is a biological clock with a physical address and a chemical announcement.

The thing that varies.

Psych 0291 Consciousness

Awareness of internal and external stimuli, varying continuously in level across a day. A dial rather than a switch — which is what makes the rest of the unit possible.

The cycle.

Psych 0293 Circadian Rhythm

A biological cycle of roughly twenty-four hours regulating sleep, temperature and alertness. Roughly is accurate — it is close to a day and not exactly one.

The clock itself.

Psych 0295 The Suprachiasmatic Nucleus

A structure in the hypothalamus serving as the brain's primary clock for that cycle. Unit Two's regulator, doing one of its specific jobs.

The signal.

Psych 0297 Melatonin

A hormone released by the pineal gland as darkness falls, signalling the body toward sleep. Light is the input, and the signal follows its absence.

Four entries on what happens when the schedule and the rhythm disagree. Two causes — one from travel, one from work — and then two entries on what accumulates, because the shortfall does not reset overnight.

After travel.

Psych 0299 Jet Lag

The mismatch between the internal rhythm and the local light-dark cycle after rapid travel across time zones. The body kept the old schedule and the world changed.

At work.

Psych 0301 Rotating Shift Work

Repeatedly forcing the sleep-wake schedule against the rhythm, producing chronic misalignment. The same mismatch as the previous entry, arranged to happen over and over rather than once.

What accumulates.

Psych 0303 Sleep Debt

The accumulated shortfall between the sleep a person needs and the sleep they get. Accumulated is the operative word — the arithmetic carries forward.

What it costs.

Psych 0305 Effects of Sleep Deprivation

Degrading attention, mood regulation and memory consolidation, and impairing performance on complex tasks. Four separate systems, and the last one is where the effect is largest.

Three entries on what sleep is for. Two theories that answer different versions of the question — one about what sleep does to the body, one about why the pattern would have survived — and then a function that is measured rather than argued about.

The first theory.

Psych 0307 Sleep as Restoration

Sleep exists to repair and replenish the body and brain after waking activity. It answers what sleep does while it is happening.

The second.

Psych 0308 Sleep as Adaptive Function

Sleep patterns evolved to keep organisms inactive and safe during their least useful hours. It answers why the pattern persisted — Unit One's evolutionary perspective, applied here.

And one measured function.

Psych 0310 Sleep and Memory Consolidation

Consolidation during sleep stabilises newly learned material into more durable long-term storage. Not a theory of why sleep exists — an observation of something it does.

Four entries laying out the architecture. Three non-REM stages in increasing depth, and then a fourth stage that most people would place at the bottom of that list and does not belong there.

The first.

Psych 0312 NREM Stage N1

The transition into sleep, with slowed brain waves and easy awakening. Short, and the boundary between waking and sleeping runs through it.

The second.

Psych 0314 NREM Stage N2

Deeper, marked by sleep spindles and reduced responsiveness to the environment. Most of a night is spent here.

The third.

Psych 0316 NREM Stage N3

Deep slow-wave sleep, the hardest stage to wake from and the one associated with physical restoration. Hardest to wake from is the definition of deepest.

And the fourth.

Psych 0318 REM Sleep

Rapid eye movements, brain activity resembling waking, and the most vivid dreaming. Every part of that description points away from depth, which is what the next entry is about.

Three entries, and the middle one is the cleanest correction in the unit. It does not argue about REM at all. It restates what the word deep means as a measurement — and once the measurement is stated, the error has nowhere left to stand.

The error.

Psych 0319 Confusing REM with Deep Sleep

Treating REM as the deepest stage of sleep because it is the stage of vivid dreaming. The reasoning is intuitive and the two properties are unrelated.

The measurement.

Psych 0320 Depth Is Not Vividness

Depth is measured by how hard a sleeper is to wake, not by how rich the experience during that stage is. Stating the measurement settles the question without needing an argument about dreams.

The safeguard.

Psych 0322 REM Atonia

Near-paralysis of the voluntary muscles during REM, preventing dreams from being acted out. A mechanism that exists because the alternative would be dangerous.

One procedure, and it puts the four stages into their actual order — which is not a descent to the bottom and a climb back. It is a repeating loop, roughly every ninety minutes, and the proportions inside it change as the night goes on.

Watch a night's structure.

Psych 0324 The Sleep Cycle

Running from the first stage down to the deepest and back up into REM, repeating roughly every ninety minutes with shifting proportions across the night. Later cycles are not copies of earlier ones.

Three entries, and the third one is a piece of intellectual honesty worth pointing at. It takes the more modern of the two theories and states what that theory does not explain — which is a rarer move than criticising the older one.

The first account.

Psych 0326 Freud's Dream Theory

Dreams expressing unconscious wishes, with manifest content disguising a latent meaning. Two layers, with the interpretation running from the first to the second.

The second.

Psych 0327 Activation-Synthesis Theory

Dreams as the cortex's attempt to make a coherent story from random brainstem activity during REM. The strangeness of dreams becomes a prediction rather than a puzzle.

And what it misses.

Psych 0328 What Activation-Synthesis Leaves Open

It accounts for the form dreams take and not for why particular material recurs across nights. Recurrence is the observation the theory does not reach, and the entry says so rather than leaving it.

Five entries. The last one separates two things that get called the same thing in conversation — and they arise from different stages of sleep, which is why one is remembered and the other is not.

The first.

Psych 0330 Insomnia

Persistent difficulty falling or staying asleep, at least three nights weekly for at least a month. The thresholds are part of the definition rather than guidance.

The second.

Psych 0332 Sleep Apnea

Breathing stopping repeatedly during sleep, producing brief arousals the sleeper does not recall. The person experiences the consequence without any memory of the cause.

The third.

Psych 0334 Narcolepsy

Overwhelming daytime sleepiness and sudden uncontrollable entries into REM sleep. A stage arriving at the wrong time rather than a shortage of sleep.

A category.

Psych 0336 Parasomnias

Unwanted behaviors or experiences occurring during sleep or in the transitions into and out of it. Defined by when they happen rather than by what they are.

And two of them.

Psych 0338 Night Terrors and Nightmares

Night terrors arise from deep non-REM sleep and are not recalled. Nightmares arise from REM and are recalled vividly. Different stages, which is why the memory differs — the previous topic's point, applied.

Four entries. What makes a substance psychoactive, and then three terms describing what continued use produces — the last of which separates two things that get treated as one.

The category.

Psych 0340 Psychoactive Drugs

A substance altering perception, mood or consciousness by acting on neurotransmitter systems. Unit Two's agonists and antagonists, met again with a different name.

The first term.

Psych 0342 Tolerance

The diminished effect of a drug after repeated use, requiring larger amounts for the original effect. The change is in the person, not the substance.

The second.

Psych 0344 Withdrawal

The set of negative symptoms appearing when regular use is reduced or stopped. Defined by what happens on removal rather than by what happens on use.

And the distinction.

Psych 0346 Physical and Psychological Dependence

Physical dependence involves tolerance and withdrawal. Psychological dependence involves emotional need in their absence. Two definitions, and the second can be present with no sign of the first.

Five entries, definitional throughout. Each class is named by what it does — reduce nervous system activity, increase it, or alter perception — and one of them works by binding the exact receptors the body's own pain relief already uses.

Downward.

Psych 0348 Depressants

Reducing central nervous system activity, slowing breathing, heart rate and reaction time. The class is defined by direction rather than by chemistry.

One of them.

Psych 0350 Alcohol

A depressant impairing judgment, coordination and memory formation in proportion to blood concentration. In proportion — the relationship is graded, not a threshold.

Upward.

Psych 0352 Stimulants

Increasing central nervous system activity, raising alertness, heart rate and energy. The mirror of the depressant class, defined the same way.

The pain class.

Psych 0354 Opioids

Relieving pain and producing euphoria by binding the receptors the body's own endorphins use. Unit Two's receptor specificity is exactly why this works — the shape already fits.

And perception.

Psych 0356 Hallucinogens

Altering perception and producing sensory experiences that do not correspond to external stimuli. Defined by the mismatch between experience and input.

Three entries closing the unit. Two states produced deliberately rather than pharmacologically — and then a capstone that takes one sleeper and follows them from the circadian signal all the way to waking, naming everything in order.

The first.

Psych 0358 Hypnosis

A state of focused attention and heightened suggestibility, induced by another person's guidance. Both halves of the description are doing work.

The second.

Psych 0360 Meditation

A practice of directed attention producing measurable changes in arousal and self-reported state. Measurable and self-reported are two separate kinds of evidence, and the entry names both.

The capstone. One night, traced.

Psych 0362 A Night of Sleep, Traced

Following one sleeper from the circadian signal to final waking, naming every stage, hormone and disruption in order. The whole unit, on one night.

Five things you can now do. You can say what sets the sleep-wake cycle — a structure in the hypothalamus keeping a roughly twenty-four hour rhythm, with melatonin signalling as darkness falls — and that travel and shift work both push a schedule against it. You can say why REM is not the deepest stage: depth is measured by how hard someone is to wake, and vividness of experience is a different property. You can state both theories of sleep's function — repair while it happens, and safety during useless hours — and that consolidation is a measured function rather than a theory. You can say what separates physical from psychological dependence: the first involves tolerance and withdrawal, and the second is emotional need without them. And you can say what separates a night terror from a nightmare — deep non-REM and not recalled, against REM and recalled vividly.