Chapter 9:Brain States 

SLEEP
  • Lack of sleep can cause depression, anxiety, impairment similar to alcohol, diabetes, high blood pressure, and cognitive impairment

Brain Activity during sleep

EEGs are used to measure electrical waves, caused by the movement of ions in and out of active neurons → brain waves

  • Slow wave sleep: high amplitude, low frequency
    • Neurons get less excited in this state
    • In sleep
    • Less frequently as you sleep
  • REM- waves look similar to waves when you are awake
    • Low amplitude(less synchronized)
    • Motor cortex fires rapidly - twitching movement
  • 90 min cycles
    • 75-80 mins SWS
    • 10-15 mins REM -more longer and stronger during morning hours

SLEEP REGULATION

  • Orexin producing neruons connecting with the forebrain use acetylcholine, norepinephrine, serotonin, and gluatamate to keep us from sleeping. Located in hypothalamus, projections sent to brain stem, spinal cord, thalamus, basal ganglia, forebrain, amygdala, and dopamine prodigies neruons
    • Increase metabolic rate triggered by low blood sugar(insulin induced)
    • In hypothalamus, the orexin neruons contain histamine, another transmitter important to stay awake
    • In SWS, acetylcholine and norepinephrine is low
    • Our arousal system is suppressed by ventrolateral preoptic nucleus(nerve cells in hypothalamus) which release GABA and galanin
    • Damage=insomnia
    • In rem acetylcholine is high, norepinephrine still low (dreaming) →forebrain stimulation → rapid eye movement

Sleep wake cycle

Circadian system(based on daylight) and Homeostatic system(how long you are awake) are independent

  • Circadian regulated by superchiasmatic nucleus in hypothalamus have a 24 cycle regulating activity, sleep, hormones release, bodily functions which receive information from the retina
    • Also connects to different Brian regions, including ventrolateral preoptic nucleus → arousal
  • Homeostatic regulates sleepiness
    • Adenosine is increased→ slow arousal
    • More sleep=less adenosine
    • Caffeine prevents adenosine from binding to receptors, preventing sleepiness
  • Less sleep→ brain gives more waves during SWS

SLEEP DISORDERS

  • Insomnia- difficulty falling asleep or waking up while asleep
  • Daytime sleepiness- feeling tired during the day → daytime accidents
  • Sleep apnea - when sleeping the throat muscles collapse and close airway. Patients have difficulty breathing and weak SWS, high blood pressure→ increase risk of heart attack
    • Many require breathing machines (CPAP machine)- continuous positive airway pressure or surgery
  • REM sleep behavior disorder- nerve pathways that prevent muscle movement don’t work→ sleepwalking. Treatment medications enhance GABA

NARCOLEPSY

  • Suddenly falling asleep during the day due to the lack to control when to sleep, caused by loss of orexin neruons.
    • Lose muscle tone while awake(cataplexy)caused by emotional response
    • By stimulating orexin and Melanin concentrated hormones it might help control the wake and sleep pattern.

AROUSAL

  • Motivation to do an action
  • Under a certain threshold→ sleep
    • Anxiety makes it hard to go under the threshold

NEUROTRANSMITTERS

  • Dopamine-movement
  • Norepinephrine-alertness
  • Serotonin-emotion
  • Acetylcholine and histamine-increase arousal

SENSORY INPUT

  • Environmental things that stimulate you are sorted in thalamus, which takes sensory inputs are wires to cortex

AUTONOMIC NERVOUS SYSTEM

  • Reticular activating system (brain stem) takes sensory signals and makes sense of them, leading them back down the body
  • Autonomic nervous system-heart rate, blood flow, breathing → physical state of arousal
  • Helps us have an emotional or physical response

SEXUAL AROUSAL

  • involves hormones like estrogen and testosterone
    • these activate the neurons that will therefore activate the receptors used in general arousal
    • likely happens in hypothalamus, amygdala(pleasure), and hippocampus, nucleus accumbens(rewards)

ATTENTION

  • changes in heart rate, breathing, and blood, like arousal. this is because we need to be alert to be aroused
  • more attention=faster processing

focus

  • voluntary (endogenous )
    • frontal and parietal lobes active when you focus on one object/thing
  • involuntary (exogenous)
    • environmental changes (distractions) cause regions in the right hemisphere to focus on it

disorders

  • attention deficit hyperactivity disorder (ADHD)
  • schizophrenia - might include selective attention failures
  • prosopagnosia
  • hemineglect - unable to recognize faces, caused by damage to right parietal
    • in some cases, patients will ignore the left side of the body and left visual field.

DEFAULT MODE NETWORK

  • when we are asleep, only certain parts of the brain are active, identified with MRI and PET scans
  • the regions of the brain associated with a certain task light up more under scans when they are active.
    • posterior area- recalling past memories
    • hippocampus- helps new memories form
    • dorsomedial- introspective