Ch 13: Sleep & Consciousness

Studying Consciousness

via:

• introspection = looking within

(-) : person could be lying or not fully aware

• studying sleep = altered state of consciousness → CAN study

Sleep - What is the Purpose of sleep?

Sleep = partially conscious & unconcious

• period of non-productivity & vulnerability

Theories of Purpose

1. Restorative function = sleep is to restore the body

support: species w higher metabolic rates sleep more

2. Adaptive Hypothesis = amount of sleep depends on availability to food & safety

ex. animals w less food available & safety → sleep more

Importance of Sleep

→ findings sorta align w restorative theory of sleep

• shift workers performance DECREASES w constant sleep schedule changes

• long-terms sleep deprivation:

  • 25% decrease in the # of neurons involved in alertness

  • rhythmic cycle impairment → DONT fully recover

  • increased risk of cancer, infection & alzhiemers

Circadian Rhythms

SCN = in the hypothalamus & acts as the biological clock

• cued by external environment (ex. light) → activates “zeitgebers” (timegivers)

  • w/o Zeitgebers: switch to a 25hr day - NOT GOOD

ex. those who work underground tend to shift to a 25hr day

ex. those who sleep during the day and work at night : still have rhythm so its ok :)

Circadian Rhythms : SCN & Melatonin

Melatonin = induces sleep

• DOESNT treat insomnia or sleep deprivation

• light resets the biological clock by SUPPRESSING melatonin secretion

  • blue light has the same effect as normal light → surpasses melatonin

  • red light DOESNT activate zeitgebers → DOESNT supress melatonin

  • blind ppl: STILL respond to light

SCN control production of melatonin → tells pineal gland to release it → feel sleepy

Ultradian Rhythms

= less than a day in length

• a basic rest & activity cycle is abt 90-100 min

for: hormone production, urinary output, alertness

Active process of sleep

• brain is STILL ACTIVE, some areas even INCREASE in activity

  • uses just as much energy while asleep

• sleep isn’t triggered by a lack of energy, but bc were not optimal so some brain structures turn on sleep

note: SCN DOESNT make us fall asleep

Studying sleep: EEG

EEG = records activity b/w electrodes → forms waves

• can also use EOG = measures eye movements

• ENG = measures jaw muscle tension

Stages of Sleep

Awake: beta waves

relaxed/drowsy awake : alpha waves

→ dream in ALL stages, but most vivid in REM

Stage 1: theta waves

• hyping/myoclonic jerks & hypnagogic imagery

• snoring

Stage 2: Sleep Spindles (short rapid activity) & K-complexes (excitation then inhibition)

• slowing of brain waves, slower heart rate, lower body temp, muscles relax, slower eye movements

Stage 3 & 4: Slow-wave sleep (~30min)

• Delta waves

• to feel rested !!

• sleep walking, bed wetting…

note: stage 4 ONLY has delta waves

Stage 5: REM (20 min-1hr)

• beta-like waves (brain looks fully awake)

• rapid eye movement, PARALYZED body, vivid dreams

note: go stage 1-4 then 2-REM

Sleep : cycle patterns

beginning of sleep: more restoration in the slow-wave stages 3-4

later: more REM

• babies spend more time in REM

• if sleep deprived : spend more time in slow wave

Functions of Sleep

→ essential to proper cognitive function

importance of non-REM:

• recovered faster than REM stage after you’ve been sleep deprived

• have increased slow-wave after exercise… or with a warm head

importance of REM:

• for memory consolidation & learning → believed to support neural development

support: babies have more REM sleep

Functions of Slow-wave sleep (stages 3&4)

• restore brain

support: sleep deprivation produce cognitive deficits

Functions of REM sleep (stage 5)

• protects consolidation in memory

support: similar activity of learning brain areas & increases in hippocampus (4-7 days to fully consolidate based on activity)

• DNA repair acceleration

support: lack of REM is assoc w poor immune system

Hypotheses of Sleeps Purpose:

1. to conserve energy

2. immobilization during sleep is adaptive bc it reduces danger

3. to restore energy & body resources

• strongest evidence

→ all are from the evolutionary perspective

Waking & Arousal Controls

via: Brain stem arousal centres = send activating signals to PPT/LDT

• PPT/LDT = rapid fire during wakefulness & REM sleep, slow during non-REM sleep

→ if lesioned: loss of wakefulness & alertness for a short period, until back up (forebrain arousal areas) take over

non-REM Sleep Controls = induce non-REM sleep

via: VLPO = inhibits wakefulness

• rapid fire during non-REM sleep → increase as sleep deepens to stage 4

REM sleep controls = non-REM → REM

via: Ponto-Geniculo-Occipital waves (PGO) = travel pons → lateral geniculate nucleus → occipital area → TURN ON REM

• begin 80 seconds before the actual start of REM → causing EEG desynchrony as it shows REM before it actually occurs

→ SLD (in pons) turn on/off PGO

KNOW THE ACTUAL PGO NAME!!!!

Sleep Disorders: Insomnia

= inability to sleep or unable to obtain restful sleep

• can sleep all night and still have insomnia if not well rested

• MOST common

• leads to increased risk of high BP, diabetes… ] these also occur in ppl that oversleep

causes: stress, poor sleep hygiene, stopping addictive sleep aids

Sleep Disorders: Sleep walking

= during stage ¾ of sleep, and complex behaviours while mostly still asleep

triggers: stress, alcohol, sleep deprivation

• common in children

• genetic link: 47% more likely if ur parent did this during childhood

Sleep Disorders: Narcolepsy

Narcolepsy = fall asleep during day → straight into REM

• can be due to low orexin

• unknown cause - but seen in dogs that lack an orexin receptor

• genetic link

comorbid w:

Cataplexy = sudden Antonia (component of REM) → fall to floor paralyzed but FULLY AWAKE

Sleep Disorders: REM Sleep Behaviour Disorder

= physically ACTIVE during REM sleep → often injure themselves or others in bed

• NOT PARALYZED DURING REM

→ ½ develop Parkinsons within 10 yrs of onset, remainder develop it later

• possibly bc of increased lewy bodies in the medulla → travel twos motor areas to cause Parkinson

Consciousness

• involves networks:

1. Salience Network = regions that detect important stimuli → say it needs attention

→ includes AIC & ACC

2. Central Executive Network = regions that control attention & working memory → make u pay attention

• salient network goes back and forth b/w default network (wakeful rest) & central executive network (when attention is required)

note: those in a coma are unconcious

Awareness vs. Attention

→ awareness is the content of consciousness, while attention is the process of selecting awareness

Awareness

• study by monitoring activity to brief word exposure:

  • no awareness of word → ONLY occipital areas is active

  • awareness of word → prefrontal & parietal cortexes are active

note: brain damage in frontal/parietal lobes can inhibit what we’re aware of (know something happened, but no what actually did)

Attention

= allocating limited resources by focusing on only some neural inputs

• a physiological process : changes in attention → change in neural activity

  • increased cortical activity due to changing thalamus activity/ how the thalamus organizes info

• 2 primary networks → talk to ACC

1. Dorsal attention network = goal-directed behaviour

ex. focus on food when ur wanting to eat

2. Ventral attention = stimulus demands

ex. focus on a fire alarm

Sense of Self

Agency = attribute an action/effect to ourselves

• shown they self-recognition - using Rouge test (babies CANT)

Brain structure associated:

• ACC & insula

  • used in self-recognition, self-description & memories

  • if damaged : fail rouge test + CANT describe themself

note: TMS to the parietal lobe reduces a persons ability to recall self-deceptive words, but they can still describe another person

→ sense of self is a CONCEPT, not a neurologically distinct entity

its includes: body image, memories & mirror neuron activity

Disorders of Self : Split brain

= may behave in 2 distinct ways

2 interpretation:

1. left hemisphere (language dominant) is the arbiter of consciousness

2. each hemisphere is capable of consciousness → get 2 selves

Disorders of Self: Dissociative Identity Disorder (DID)

= shifts in consciousness & behaviour that appear to be distinct personalities or selves

• severe form of PTSD? ] use similar treatments & have ~identical brain changes

• used to be misdiagnosed as schizo

→ Body CAN physically change b/w personalities

ex. one personality could actually need insulin… wtf