sleeping and dreaming

Phase advance

Rising early or retiring to bed earlier than normal.

Shift work

A work schedule that disrupts normal sleep cycles, often leading to accidents.

Chernobyl accident timing

Occurred between 1am & 4am.

Lorry accidents timing

Most occur between 4am & 7am.

Economic impact of shift work

Costs the US $77 billion annually due to accidents and medical expenses.

Hawkins and Armstrong-Esther study

Studied 11 nurses during a 7 night rotation; performance was significantly impaired on the first night.

Sleep in newborn infants

16-18 hours per day throughout the day.

Sleep in 16 weeks old infants

14-15 hours per day with a diurnal pattern.

Sleep in 3-5 years old children

10-12 hours per day with a biphasic pattern.

Sleep in adolescence

~8 hours per day with a monophasic pattern.

Sleep in old age

Amount of nocturnal sleep decreases to 6-7 hours and becomes more fragmented.

Suprachiasmatic nucleus (SCN)

Part of the hypothalamus that controls circadian rhythms of sleep and temperature.

Damage to the SCN

Results in less consistent body rhythms that are not synchronized to environmental light and dark patterns.

SCN neuron firing pattern

Cells in the SCN fire their action potentials in a particular rhythm.

Effect of light on SCN

Light resets the SCN via the retinohypothalamic path.

Retinohypothalamic path

A pathway that travels directly from the retina to the SCN.

Melanopsin

A photopigment in retinal receptors that respond directly to light.

Blind mole rats

Have eyes but no muscles to lift the lids, nor lenses.

Melanopsin cells

Cells that are fully functional in the absence of functioning rods and cones.

Pineal Gland

Located posterior to the thalamus and secretes melatonin, a hormone that increases sleepiness (2-3 hrs before bed).

Melatonin

A hormone that increases sleepiness and regulates circadian and circannual rhythms.

Circadian Rhythm Genes

Two types of genes responsible for generating the circadian rhythm: Period (produces proteins called PER) and Timeless (produces proteins called TIM).

PER Protein

Produced by the Period gene; interacts with TIM to induce sleepiness when concentrations are high.

TIM Protein

Produced by the Timeless gene; interacts with PER to induce sleepiness when concentrations are high.

Clock Gene Damage

Results in reduced sleep and erratic sleep patterns.

Mutations in PER Gene

Result in odd circadian rhythms and shifts in the circadian rhythm.

EEG

Measures continuous recording of electrical activity in the brain, detecting changes in the potential of postsynaptic neurons.

Polysomnography

Includes brain electroencephalograms (EEGs), muscles electromyograms (EMGs), heart electrocardiograms (ECGs), and eye movement electro-oculograms (EOGs).

Actigraph Watch

A recording device with an accelerometer (movement sensor) and light sensor.

EEG Equipment

Relatively cheap, low invasiveness, and can be used to study brain activity over an extensive length of time.

EEG Measurement

Patterns of neurons firing are associated with different states of cognitive functioning, measured in frequency (Hertz - Hz) and amplitude.

Stage 1 Sleep

Characterized by irregular, jagged, low voltage waves; represents 5% of sleep time.

Stage 2 Sleep

Beginning of 'true sleep' with sleep spindles and K-complex; represents 50% of sleep time.

Stage 3 Sleep

Slow wave sleep (SWS) with large amplitude delta waves; represents 15-20% of sleep time.

REM Sleep

Rapid Eye Movement sleep, characterized by irregular, low-voltage, fast EEG waves; represents 20-25% of sleep time.

Stages of Sleep

Early (more NREM) and late (more REM) phases of sleep.

Hypnos

The God of Sleep.

Constantin von Econom (1917)

Studied the brains of those who died from the Spanish flu, observing lethargy or coma before death.

Wakefulness Centre

Located at the posterior hypothalamus or the upper midbrain, associated with lethargic and comatose patients.

Sleep Centre

Located at the preoptic area of the anterior hypothalamus, associated with sleepless patients.

Reticular Formation

Part of the brainstem that plays an essential role in maintaining wakefulness.

Inhibitory Neurotransmitters

GABA decreases temperature and metabolic rate, reducing neuron stimulation.

Excitatory Neurotransmitters

Includes Acetylcholine, Norepinephrine, Histamine, and Orexin, which increase arousal and maintain wakefulness.

Norepinephrine

A neurotransmitter associated with the Locus Coeruleus (LC) and excitatory connections.

REM Sleep

Characterized by increased activity in the pons, limbic system, parietal cortex, and temporal cortex, with decreased activity in the primary visual cortex.

PGO Waves

Pons-Geniculate-Occipital waves associated with REM sleep.

Evolutionary Theory of Sleep

Suggests sleep conserves energy and varies by species' food acquisition needs and predator awareness.

Repair and Restoration Theory

Proposes sleep allows the body and brain to repair after exertion.

Evidence Against Repair and Restoration Theory

Adverse effects of sleep deprivation are not permanent and do not correlate with performance deficits.

Improving Cognitive Function

Sleep enhances memory, decision-making, and other executive functions.

Sleep-dependent Memory Processing

Refers to memory consolidation that occurs during sleep.

Sleep Deprivation Effects

Can lead to irritability, dizziness, hallucinations, and impaired concentration.

Sleep Duration and Performance

No correlation between sleep deprivation duration and performance deficits.

Environmental Cues and Sleep

In environments without external cues, sleep tends to be shorter after long wakefulness.

Body Temperature During Sleep

Decreases during sleep as part of energy conservation.

Cognitive Effects of Sleep

Sleep is crucial for cognitive processes including memory and emotional regulation.

Two-stage model of memory consolidation

A theoretical framework explaining how memories are processed and stored in the brain.

neocortex

The part of the brain involved in higher-order brain functions such as sensory perception, cognition, and motor control.

hippocampus

A region of the brain associated with memory formation and spatial navigation.

Sleep-dependent memory processing (System Consolidation)

The process by which memories are re-activated and redistributed during sleep.

Transcranial Alternating Current Stimulation (tACS)

A non-invasive brain stimulation technique that modulates neuronal activity using alternating current.

Delayed sleep phase syndrome (DSPS)

A disorder characterized by an inability to awaken and fall asleep at socially acceptable times, affecting circadian rhythms.

Hypopnea syndrome

Abnormally shallow breathing or slow respiratory rate while sleeping.

Sleep apnea

A sleep disorder characterized by obstruction of the airway during sleep, leading to insufficient deep sleep.

Narcolepsy

A neurological disorder characterized by excessive daytime sleepiness and spontaneous sleep attacks.

Sleepwalking or somnambulism

A behavior disorder that originates during sleep and results in walking or performing other complex behaviors while asleep.

Parasomnias

Disruptive sleep-related events involving inappropriate actions during sleep, such as sleepwalking and night terrors.

Primary insomnia

Chronic difficulty in falling asleep and/or maintaining sleep without any identifiable cause.

Periodic limb movement disorder (PLMD)

A sleep disorder characterized by sudden involuntary movements of the limbs during sleep.

Restless legs syndrome (RLS)

A disorder characterized by an irresistible urge to move the legs, often associated with PLMD.

Sleep paralysis

A temporary inability to move or speak while falling asleep or waking up, often accompanied by hallucinations.

Night terror

A sleep disorder characterized by abrupt awakening from sleep with intense fear and panic.

Dreaming

The experience of visual, auditory, and sensory events during sleep, often occurring during REM sleep.

REM

Rapid Eye Movement sleep, a sleep stage characterized by quick movements of the eyes and vivid dreaming.

Lucid Dreaming

A state of consciousness where the dreamer is aware that they are dreaming and may have some control over the dream.

Activation-Synthesis Hypothesis

A theory suggesting that dreams are the brain's attempt to make sense of random neural activity during sleep.

Neurocognitive Hypothesis

A theory proposing that dreams are a form of thinking that occurs under unusual conditions, integrating memories and sensory information.