Chapter 4: Consciousness

Sleep experiences as a pause in daily life.
Consciousness: Awareness of internal (feelings of hunger, pain) and external stimuli (light detection).
Wakefulness: High levels of sensory awareness, thought, and behavior.

A biological rhythm is an internal cycle of biological activity.
- Fluctuations include body temperature, menstrual cycles, and levels of alertness.
- Circadian rhythm: Biological rhythm occurring approximately every 24 hours.
- Generated by the suprachiasmatic nucleus (SCN).
- Sleep-wake cycle linked to the natural light-dark cycle of the environment.
Hypothalamus: Responsible for maintaining homeostasis, or balance within a biological system.

Circadian changes in body temperature over a 28-hour period illustrate how it peaks during the day and drops during sleep, especially in the early morning.

Located in the hypothalamus, the SCN acts as the brain's clock mechanism.
Sets itself with light information from projections from the retina, which helps synchronize it with the external environment.

Melatonin: A hormone regulating the sleep-wake cycle.
- Stimulated by darkness, inhibiting light.
- Released by the pineal gland.
Sleep regulation: Control of switching between sleep and wakefulness, aligning with external cues.
Each person has a unique activity pattern called a chronotype.

Devices provide bright light exposure to help maintain a regular circadian cycle, important for those with night shifts or seasonal affective disorders.
Jet lag: Symptoms arise from the mismatch between internal circadian cycles and the environment, which can include fatigue, irritability, and insomnia.
Rotating shift work: Changing schedules disrupt normal circadian rhythms, leading to exhaustion, agitation, and potential depression/anxiety.
Bright light exposure can realign biological clocks.

Negative consequences like cognitive deficits affect various body systems.
Sleep debt: Result of chronic insufficient sleep.
Sleep rebound: Indicates sleep deprivation leads to quicker return to sleep in subsequent opportunities.

Polysonograph (PSG): Recording many physical variables during sleep, showing signals such as EEG outputs, body temperature, muscle activity, and heart rates.
Sleep: Defined by relatively low physical activity and reduced awareness.
Controlled by brain regions: thalamus (slow-wave sleep) and pons (REM sleep).
Associated with hormone regulation, including:
- Melatonin
- Follicle stimulating hormone
- Luteinizing hormone
- Growth hormone

Adaptive Function: Sleep restores resources expended during the day and serves as an adaptive response to predatory risks.
Cognitive Function: Sleep is crucial for memory formation and cognitive functions. Research indicates:
- Sleep deprivation disrupts cognition leading to memory deficits.
- Impairments worsen with increased deprivation, particularly affecting slow-wave sleep crucial for memory.
Benefits of Sleep:
- Maintains healthy weight
- Reduces stress levels
- Improves mood
- Increases motor coordination
- Enhances cognition and memory formation

Brain wave activity visualized via EEG differs across sleep stages:
- Alpha: Low frequency, high amplitude, synchronized.
- Theta: Low frequency, low amplitude.
- Delta: Low frequency, high amplitude, desynchronized.

Stage 1: Transitional phase from wakefulness to sleep:
- Decreases in respiration rate, heartbeat, and muscle tension.
- Alpha waves observed.
Stage 2: Deep relaxation:
- Characterized by theta waves, sleep spindles, and K-complexes:
- Sleep spindles: Rapid high-frequency brainwave bursts.
- K-complexes: High amplitude patterns of brain activity.

Characterized by rapid eye movements, paralysis of voluntary muscles, and dreams.
Brain waves during this phase resemble those during wakefulness.

Defined as difficulty falling or staying asleep for at least three nights weekly over a month, often linked to depression.
Contributing factors:
- Age
- Drug use
- Exercise habits
- Mental status
- Bedtime routines
Treatment:
- Stress management
- Addressing behavior patterns leading to insomnia
- Cognitive-behavioral therapy focusing on cognitive processes and maladaptive behaviors.

Involves unwanted motor behaviors during sleep, including:
- Sleep walking: Typically during slow-wave sleep.
- REM sleep behavior disorder: Active behaviors during REM due to lack of muscle paralysis; treated with Clonazepam.
- Restless leg syndrome: Uncomfortable leg sensations relieved by movement; treatable by medications.
- Night terrors: Panic reactions with screaming during NREM sleep.

Characterized by pauses in breathing during sleep, lasting 10-20 seconds or longer.
Results in sleep disruptions, leading to fatigue; more prevalent in overweight individuals.
Types include:
- Obstructive: Blockage of airways.
- Central: Central nervous system fails to prompt breaths.
Treatment: Continuous Positive Airway Pressure (CPAP) devices.

Campaigns like Safe to Sleep aim to educate on reducing SIDS risk factors, especially in infants under 12 months - higher risk in boys.
Contributing factors include:
- Premature birth
- Smoking exposure
- Overheating or hyperthermia

Irresistible urge to sleep during waking hours, often linked with heightened stress/arousal.
- Cataplexy: Loss of muscle tone or paralysis while awake.
- Hypnagogic hallucinations: Vivid, dream-like experiences.
Treatment: Psychomotor stimulant drugs.

Defined by compulsive drug use despite negative consequences, including both physical and psychological dependence.
- Physiological dependence: Changes in bodily functions and withdrawal symptoms.
- Psychological dependence: Emotional needs for the substance.
- Tolerance: Requirement for increased drug amounts for the same effects.
- Withdrawal: Negative symptoms when discontinuing the substance.