PSYC201: Tue 29/04 W8;L22

Announcements

• Psych Society Quiz Night: Next Wednesday at the Hunter Lounge, doors open at 5:00 PM, quiz starts at 5:30 PM. Prizes include snack food packages and free pizza.

Neurobiology of Mental Health Conditions - Topic Selection

• Students to rank topics for the final week's lectures.
• Options include: addiction, anxiety disorders, depression, schizophrenia, and autism spectrum disorders.
• Addiction was consistently the top topic in previous years.
• Selected Topics: Addiction and possibly Anxiety Disorders or ADHD.

Introduction to Sleep

• Sleep is a universal behavior across organisms.
• Sleep duration varies significantly across species (e.g., lions sleep 22 hours/day).
• Some animals adjust sleep patterns seasonally (e.g., migratory birds).
• Importance of Sleep: Genetic conditions causing complete insomnia lead to rapid health decline and premature death.

Key Figures in Sleep Research

• Michel Jovet: Discovered paradoxical sleep using EEG, noting brain activity similar to wakefulness during deep sleep.
• Nathaniel Kleitman and Eugene Azerinsky: Discovered REM sleep through observations of rapid eye movements and EEG recordings.

REM Sleep

• Characterized by rapid eye movements and brain activity similar to wakefulness.
• Associated with dreaming, although dreaming also occurs in non-REM sleep.

Biological Rhythms

• Biological rhythms occur in various parameters, not just day and night.

• Annual Rhythms (Circannual Rhythms): Seasonal changes in behavior.

  • Example: Migratory birds show increased activity before migration, even in controlled environments.

• Example: Dogs maintain winter/summer fur cycles regardless of hemisphere.

• Circadian Rhythms: Rhythms over a 24-hour period.

  • Examples:
    • Body temperature fluctuates consistently.
    • Cortisol levels peak around noon and are lower during sleep.
    • Mood varies throughout the day.
  • These rhythms influence various behaviors, biological parameters, and molecular changes.

Circadian Clock

• Not perfectly 24 hours; requires adjustment.
  • Studies in constant darkness show a shift in activity patterns.
  • Antarctica studies and astronaut studies demonstrate disruption due to lack of normal light/dark cycles.
• Zeitgebers (Time Givers): Environmental cues that synchronize the biological clock.
  • Light is the most important zeitgeber.
  • Daylight Savings Time changes disrupt the biological clock, causing adjustment periods.
  • Example: People in East Germany wake up earlier than those in West Germany due to earlier sunrise.
• Other factors influencing sleep: exercise, temperature, meals, and noise.

Changes in Circadian Rhythms Over Time

• Sleep patterns change with age.
• Infants sleep more; older adults sleep less and have more fragmented sleep.
• Midpoint of sleep (mid-sleep time) varies with age, peaking around age 20.
• Slight differences between males and females in sleep patterns.

Sleep Stages and Measurement

• Measured using EEG (electrical activity on the skull) and EOG (electrooculogram, measuring eye movement).

• Sleep Stages:

  • Awake State: High electrical activity and eye movements.
  • Stage 1 Sleep: Decreased EEG activity and smaller eye movements.
  • Stage 2 Sleep: Characterized by sleep spindles (rapid EEG activity) and K complexes (slower activity).
    • Sleep spindles are associated with thalamus-cortex information exchange and are important for learning and memory.
  • Slow Wave Sleep: Slow and regular EEG activity.
  • REM Sleep: Rapid EEG activity and eye movements.

• Sleep Cycle: Progresses from stage 1 to stage 2 to slow wave sleep and then to REM sleep, cycling throughout the night.

• Differences in Sleep Patterns Between Young and Older Adults:

  • Older adults have more frequent awake periods.
  • Older adults have less slow wave sleep.
  • REM sleep remains relatively consistent.

Brain Mechanisms of Sleep

• The suprachiasmatic nucleus (SCN) in the hypothalamus is the primary biological clock.
• The SCN has an inherent 24-hour rhythm, even when isolated.
• Receives direct input from the retina via ganglion cells, which contain light-sensitive pigments.
• Ganglion cells are slow to activate and extinguish, sensitive to blue light.
• Blue light from electronic devices can interfere with sleep by affecting the SCN.

Molecular Mechanisms

• Clock, PER, and TIM proteins regulate the circadian rhythm.
• PER and TIM concentrations fluctuate over a 24-hour cycle.
• Clock stimulates PER and TIM production.
• PER and TIM inhibit Clock.

Interaction of Clock, PER, and TIM

• The interaction of Clock, PER, and TIM can be simply represented as:

  $Clock \rightarrow PER \&\ TIM \dashrightarrow inhibit \ Clock$

• In morning: PER and TIM are low, so Clock is high.

• Clock activates PER and TIM, increasing their levels.

• In evening: High levels of PER and TIM inhibit Clock, reducing its activity.

• Cycle continues, creating a 24-hour rhythm.

Other Brain Regions

• Pineal Gland: Produces melatonin, which helps maintain sleep.
  • Melatonin is often used for jet lag.
  • Some antidepressants increase melatonin production.
  • Caffeine inhibits melatonin production, promoting wakefulness.
• In diurnal animals, melatonin stimulates sleeping, while in nocturnal animals, it stimulates wakefulness.