Sleep Science Quiz

Course Information

• Class: Year 2, Semester 1
• Course: CNS
• Code: CNS
• Title: Consciousness, Unconsciousness, Sleep & EEG
• Lecturer: Dr. Melanie Föcking (RCSI-IE), Dr. Colin Greengrass (RCSI-BH)
• Date: 08.11.2023

Learning Objectives

• ALO167: Define consciousness and unconsciousness and describe coma, vegetative state and brain death
• ALO168: Characterise circadian rhythms, ultradian rhythms and sleep stages
• ALO169: List neurophysiological measurements to characterise sleep stages
• ALO170: Recall benefits of sleep
• ALO171: Describe the regulation of sleep-wakefulness cycle
• ALO172: List sleep disorders

Defining Consciousness, Unconsciousness, Coma, Vegetative State, and Brain Death

• ALO 167: Define consciousness and unconsciousness and describe coma, vegetative state and brain death

O-PET fMRI

• Cerebral metabolism in conscious healthy individuals, patients in vegetative state, patients in locked-in syndrome and patients in a minimally conscious state
• Colour scale represents mg glucose metabolised per 100 g of brain tissue per minute

Consciousness

• Definition: A state of self-awareness, perception, ability to respond to stimuli, ability to act with judgement
• Features: Awareness of surroundings, thoughts, feelings, and memories. Awareness of one's internal sensations, thoughts and experiences. Encompasses ability to perceive, communicate and exhibit purposeful behaviour

Sleep

• Sleep is a state of changed consciousness from which a person can be aroused by stimulation.
• Alternating in a 24-hour cycle (circadian rhythm) with wakefulness
• A physiological state

Unconsciousness

• Definition: A temporary or prolonged state in which there's a lack of responsiveness to external stimuli and an absence of voluntary actions.
• Features: Absence or disruption of consciousness where an individual cannot respond to external stimuli

Coma

• Definition: A state of profound unconsciousness characterised by inability to sense and respond to external stimuli and loss of sleep-wake-cycle
• Features: A profound state of unresponsiveness caused by injury, disease, or toxins where an individual shows no spontaneous movements, does not respond to painful stimuli, and cannot be awakened.
• Mechanism: Often involves injury to both cerebral hemispheres or the reticular activating system in the brainstem
• Causes: Intoxication, acute neurological injuries, metabolic disorders, CNS infection, stroke, hypoxia
• Duration: Generally, few days to few weeks (2-5 weeks). Some patients progress to a vegetative state or die.

Glasgow Coma Scale (GCS)

• Traumatic brain injury is graded as mild, moderate, or severe based on the level of consciousness or Glasgow coma scale
• Severe: GCS 3-8
• Moderate: GCS 9-12
• Mild: GCS 13-15

Spectrum of Consciousness

• Describes the range of consciousness levels from fully alert to persistent vegetative state and death
• Includes: Fully Alert and Attentive, Delirium, Locked-in Syndrome, Minimally Conscious State, Persistent Vegetative State, Acute Coma, Prolonged Coma and Brain Death
• Behavioural and Neurological Responsiveness are crucial measurements differentiating between the states

Circadian Rhythms, Ultradian Rhythms, and Sleep Stages

• ALO168: Characterise circadian rhythms, ultradian rhythms and sleep stages
• Circadian rhythm is a cycle that lasts approximately a day/24 hours
• Ultradian rhythm occurs many times within the span of a day
• Infradian rhythms are naturally occurring cycles in the human body that last longer than 24 hours but shorter than 1 year

Circadian Rhythms

• Definition: Biological processes that display an endogenous oscillation of about 24 hours.
• Mechanism: Regulated primarily by the suprachiasmatic nucleus (SCN) of the hypothalamus.
• Features: Roughly 24-hour cycles regulating physiological processes, influenced by the natural environment (e.g., light-dark cycles).

Ultradian Rhythms

• Definition: Biological processes that display an endogenous oscillation several times within 24 hours.
• Mechanism: Several hormonal feedback loops, NREM/REM sleep cycle, Hunger Cycles
• Features: Occurring several times with a 24-hour period

Sleep Stages

• Definition: The distinct patterns of brain wave activity during sleep.
• Includes: NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement) sleep.
• NREM sleep has 4 stages, each deeper than the last
• REM sleep has a low amplitude, high-frequency activity pattern

Neurophysiological Measurements for Sleep Stages

• Neurophysiological measurements are used to characterise sleep stages
• These measurements include EEG, EOG, and EMG. EEG measures brain wave activity

Electroencephalogram (EEG)

• Main clinical applications: Epilepsy diagnosis, sleep disorder diagnosis, coma/altered state assessment, brain death confirmation
• Different wave patterns like Beta and Alpha distinguish stages of wakefulness and different states of sleep

Electrooculogram (EOG)

• Monitors eye movements, especially during REM phases

Electromyogram (EMG)

• Assesses skeletal muscle activity, decreasing as sleep deepens. Reduced activity indicates deep NREM sleep, no activity indicates REM sleep

Benefits of Sleep

• ALO 170: Recall benefits of sleep
• Cognitive Benefits: Memory consolidation, glymphatic clearance, neurogenesis
• Physiological Benefits: Cellular regeneration, immune modulation, endocrine homeostasis, muscle recovery, energy rebalance, glycaemic control and cardiovascular equilibrium

Effects of Sleep Deprivation

• Cognitive impairment, mood disturbances, physical health risks, immune system suppression, and impaired metabolism

Importance of REM Sleep

• Memory consolidation, emotional regulation, dreaming, and motor skill learning

Regulation of Sleep-Wakefulness Cycle

• ALO 171: Describe the regulation of sleep-wakefulness cycle
• Reticular Activating System (RAS) located in the brain stem, is network of neurons playing a crucial role in controlling arousal and wakefulness. The RAS projects to various brain regions influencing transitions between consciousness levels
• Neurotransmitters like acetylcholine, noradrenaline, serotonin, and histamine play a role in promoting wakefulness and alertness.

Regulation of the Sleep-Wake Cycle

• Suprachiasmatic Nucleus (SCN) located in the hypothalamus acts as central regulator of circadian rhythm and sleep/wake cycle
• SCN receives input from light sensitive cells in the retina. Melatonin controls sleep/wake regulation, produced by the pineal gland and rises in evening to promote sleepiness
• Adenosine builds up during wakefulness and increases the "sleep pressure" to promote sleep further

Sleep Disorders

• ALO 172: List sleep disorders. Includes: Insomnia, Excessive daytime sleepiness (EDS), Sleep Apnea, Narcolepsy, Parasomnias (such as Night terrors, Sleep walking and Sleep Talking), and Restless Leg syndrome

Developmental Aspects

• Sleep patterns change with age. Neonates have a lot more REM sleep compared to adults who sleep less in REM sleep.

Test your knowledge on sleep patterns, particularly focusing on REM sleep, EEG functions, and biological rhythms. This quiz will challenge your understanding of different sleep stages and their characteristics. Perfect for students of psychology and biology alike!