STAGES OF WAKEFULLNESS / SLEEP

Question 1

Electro-Encephalogram (EEG)

Answer 1

used to characterize brain activity during different states of wakefulness/sleep

• Gross average of the electrical potentials of the neurons in a general area of the brain (mostly Neocortex)
• Electrodes attached to scalp record Frequency & Voltage
• Simultaneous changes in potential
• Neural de-synchrony
• Neural synchrony

Question 2

Simultaneous changes in potential (negative graphed above zero axis, positive below) summate such that…

Answer 2

• Neural de-synchrony => High Frequency

- Neural synchrony => Low Frequency,

Question 3

Neural de-synchrony

Answer 3

High Frequency (w/variable Voltage) waves = Multiple sources of stimulation: “many pebbles”

Question 4

Neural synchrony

Answer 4

Low Frequency, High Voltage waves = Coherent source of stimulation: “one big rock”

Question 5

Awake, active

Answer 5

=> Beta Activity = 18-24 Hz, Very high frequency - very desynchronized

Question 6

Awake, relaxed

Answer 6

=> Alpha Activity = 8-12 Hz, Like above, but somewhat lower frequency, somewhat desynchronized

Question 7

Sleep 1

Answer 7

=> Theta Activity = 4-7 Hz, Lower freq, still quite irregular, significantly more synchronized

Question 8

Sleep 2

Answer 8

=> Mostly Theta Activity, but with many interspersed Spindles and K Complexes

Question 9

Sleep 3

Answer 9

=> Delta Activity = < 4 Hz observed in less than 50% of this stage, Very low freq, higher voltage, very synchronized

Question 10

Sleep 4

Answer 10

=> Delta Activity, in more than 50% of this stage, hardest to wake Stages 3 and 4 = Slow Wave Sleep (SWS)

• Heart rate and breathing rate also decrease, and brain is less responsive to external stimuli

Question 11

REM (Rapid Eye Movement) or “Paradoxical Sleep”

Answer 11

because of contradictory set of conditions that occur:

• EEG is desynchronized, High freq (like Sleep 1 or even Awake), Low voltage (only Sleep 1 is lower): “Imaginary pebbles?!”
• Heart rate, breathing rate, blood pressure more variable than in other sleep stages
• Eyes move, genitalia active, but postural muscles paralyzed, loss of muscle tonus thru most of body (=Atonia),
• External stimuli detected, will awaken if meaningful (e.g. name) but otherwise may not, incorporate into dreams instead
• Highly correlated (tho not 100%) with dreaming – i.e. with “story” dreams
• Some dream imagery in other stages: e.g. Night Terrors (scream awake, but w/out narrative nightmare) occur during Stage 4

Question 12

Sleep Cycle

Answer 12

= 90 Minutes from Stage 1 to REM: Stage 1, 2, 3, 4, 3, 2, REM, 2, 3, 4, 3, 2, REM, 2, 3, 2, REM, 2, REM . . .
- Stage 4 becomes increasingly shorter as night goes on, drops out altogether after 2-3 cycles, then Stage 3 drops out

• REM becomes increasingly longer as night goes on

Question 13

Sleep deprivation=

Answer 13

=> Lethargy, poor conc, irritability; Inc temp, metabolism & appetite; Decreased resistance to infection

• When allowed sleep, don’t sleep overall much longer, but longer in Stage 4 and especially REM (REM Rebound)

Question 14

REM deprivation:

Answer 14

Wake subject when EEG = REM (or when atonia makes cat fall off platform into water)

• System attempts to enter REM more & more frequently; When allowed to REM, shows Rebound effect
• If continuously deprived =>Irritable, poor concentration, anxious => Psychosis, hallucination, death

Question 15

Functions of Sleep & Dreaming

Answer 15

• ?! Controversial
• Sleep is restorative. But not clear why some species (e.g. prey) can sleep so much less than others (e.g. predators)
• Dreaming warms sleeping brain; Some evidence it helps consolidate memory; May help resolve psychol conflict

Question 16

Neural control of sleep…

Answer 16

• PreOptic Area of Basal Forebrain Area
• Locus Coeruleus (=“Dark Blue Place”) in Pon
• PGO Wave
• Raphe Nuclei

Question 17

• PreOptic Area of Basal Forebrain Area

Answer 17

which also assesses & regulates body temp, is critical in initiating sleep

-i.e. VLPA (Ventro-Lateral Preoptic Area) releases GABA, inhibiting all Brainstem and Forebrain arousal systems

Question 18

• Locus Coeruleu

Answer 18

(=“Dark Blue Place”) in Pons is one target of this inhibition

• Its release of NE decreases radically during sleep, virtually none during REM
• Insufficient output for normal role in forming memories => perhaps why we so easily forget dreams?

Question 19

PGO Waves

Answer 19

Sequence of activation in Pons => (Lateral) Geniculate => Occipital Cortex - initiates REM
- Excitatory ACh arouses (desynchronizes) visual (& other sensory/motor) pathways

• Also includes activation of Cranial Nerves from Tegmentum for Rapid Eye Movement
• Also sends descending signal => Medulla => Inhibit Motor Neurons in spine = Atonia (muscle paralysis)
• Prevents dreamer from acting out dreams - If malfunctioning, may result in Sleepwalking

Question 20

Excitatory ACh arouses

Answer 20

(desynchronizes) visual (& other sensory/motor) pathways
- ACh builds up just before REM, holds steady during, then drops off radically as REM ends

• Also includes activation of Cranial Nerves
• Also sends descending signal => Medulla => Inhibit Motor Neurons in spine = Atonia (muscle paralysis)

Question 21

• NOTE: Higher sensory areas of cortex all active during REM
  but NOT

Answer 21

primary NOT projection areas (V1, A1, S1 etc) since no external input being received

and NOT Prefrontal Cortex (perhaps why dreams do not follow the “rules” of normal existence?)

Question 22

activation of Cranial Nerves

Answer 22

from Tegmentum for Rapid Eye Movement

Question 23

descending signal =>

Answer 23

=> Medulla => Inhibit Motor Neurons in spine = Atonia (muscle paralysis)

• Prevents dreamer from acting out dreams - If malfunctioning, may result in Sleepwalking

Question 24

Raphe Nuclei

Answer 24

(medial Pons - Damage = no sleep)

Decreasing Serotonin (5HT) output > sleepiness, irritability if not sleep

• 5HT very low during sleep, none during REM, then Raphe produces sudden, strong burst of 5HT, shuts REM off
• 5HT gradually falls, shifting system back into Slow Wave sleep. When 5HT flat, PGO again initiated by Pons via ACh

Question 25

5HT

Answer 25

very low during sleep, none during REM, then Raphe produces sudden, strong burst of 5HT, shuts REM off

• gradually falls, shifting system back into Slow Wave sleep. When 5HT flat, PGO again initiated by Pons via ACh

Question 26

Decreasing Serotonin (5HT) output >

Answer 26

sleepiness, irritability if not sleep

Question 27

SO, stages of sleep are controlled by an

Answer 27

gain initiated by Pons via ACh

SO, stages of sleep are controlled by an i

Question 28

Neural synchrony

Answer 28

Low Frequency, High Voltage waves = Coherent source of stimulation: “one big rock”

Question 29

Neural de-synchrony

Answer 29

=> High Frequency (w/variable Voltage) waves = Multiple sources of stimulation: “many pebbles”

Question 30

Frequency

Answer 30

(# changes in average potential/time)

Question 31

Voltage

Answer 31

average amplitudes

Question 32

Simultaneous changes in potential

Answer 32

(negative graphed above zero axis, positive below)

Question 33

Spindle and K Complex =

Answer 33

intermittent bursts of high freq or voltage, as brain settles into deeper sleep

Question 34

as move into deeper sleep,

Answer 34

freq decreases & voltage increases as brain activity becomes synchronized