Sleep Disorders and Neuropsychology Quiz

Study Notes

Sleep is a complex process with different stages regulated by neural and physiological mechanisms
Understanding sleep requires exploring brain structures, neurochemicals, and processes involved in transitioning between stages

Sleep cycle consists of Non-Rapid Eye Movement (NREM) and Rapid Eye Movement (REM) sleep
NREM and REM alternate throughout the night in cycles
- NREM Sleep
  - Stage 1 (N1): Transition stage between wakefulness and sleep, light sleep with theta waves (3-8 Hz)
  - Stage 2 (N2): Deeper stage of light sleep with sleep spindles and K-complexes
  - Stage 3 (N3): Deep sleep, or slow-wave sleep (SWS), characterized by delta waves (0.5-4 Hz) essential for restorative functions (tissue growth, repair, memory consolidation)
- REM Sleep
  - REM sleep occurs primarily after NREM sleep, associated with vivid dreams, rapid eye movement, low muscle tone, and brain activity resembling wakefulness (beta waves 12-30 Hz)
- REM sleep is crucial for learning, memory, and emotional regulation, occurring about 20-25% of sleep time for adults and typically appears 90 minutes after falling asleep, repeating multiple times per night
  - Sleep cycle typically lasts around 90 minutes, with NREM and REM alternating regularly, and a typical night's sleep will have between four and six such cycles, with more deep sleep earlier and more REM sleep later.

Brain Regions
- Suprachiasmatic Nucleus (SCN): Located in the hypothalamus, acts as the body's biological clock regulating sleep-wake cycle based on light-dark cues, controls melatonin release from the pineal gland.
- Hypothalamus: Regulates sleep through sleep-promoting substances and sleep-inducing brain areas
- Reticular Activating System (RAS): A network in the brainstem that regulates wakefulness and arousal; helps facilitate sleep.
- Thalamus: Blocks sensory information from reaching the cortex during NREM sleep, so the brain can focus on internal processes instead.
- Amygdala: Involved in processing emotions, active during REM sleep, and plays a role in emotional regulation through dreaming
Neurotransmitters
- GABA (Gamma-Aminobutyric Acid): Inhibitory neurotransmitter that initiates and maintains NREM sleep
- Adenosine: Byproduct of energy consumption, promotes sleep by inhibiting wake-promoting neurons.
- Melatonin: Hormone produced by the pineal gland that signals sleep onset and regulates the circadian rhythm
- Orexin (Hypocretin): Promotes wakefulness, prevents transitions to REM sleep, dysfunction can lead to narcolepsy
Neurochemicals
- Acetylcholine: High levels during REM sleep affecting dream-related brain activity and memory processing.
- Serotonin and Norepinephrine: Active during wakefulness, but suppressed during REM sleep affecting mood and alertness.

Disruptions to normal sleep patterns or the sleep cycle lead to various sleep disorders
- Parasomnias: Abnormal behaviors during sleep (sleepwalking, night terrors, sleep paralysis) disrupting cognitive performance, and emotional stability.
- Circadian Rhythm Disorders: Problems with the timing of sleep (Jet lag, shift work disorder, delayed sleep phase syndrome) leading to cognitive impairment and mood disturbances.
- Insomnia: Difficulty falling asleep, staying asleep, or waking up too early. Chronic insomnia can affect attention, memory, and executive functioning.
- Sleep Apnea: Characterized by repeated interruption of breathing during sleep due to airway obstruction or central nervous system issues leading to fragmented sleep, daytime sleepiness, and cognitive deficits.