1
Q
EEG (Electroencephalography)
A
- Electrical recording of major changes in the brain during night’s sleep.
- EEG signals associated with being awake are different from those found during sleep
- can measure Different stages of sleep
2
Q
EMG (Electromyography)
A
- Electrical recording of muscle activity
- used because muscle tone also differs between wakefulness and sleep.
- EMG differences within sleep, depending upon the stage of sleep
3
Q
EOG
A
- Electrical recording of eye movements during sleep
- Very specific measurement that helps identify (REM)
- Eye balls make characteristic movements
4
Q
alpha activity
A
IN WAKEFULNESS STAGE
- Smooth electrical activity
- associated with a state of relaxation.
5
Q
beta activity
A
IN WAKEFULNESS STAGE
- Irregular electrical activity
- associated with a state of arousal
6
Q
Theta activity
A
IN STAGE 1
- slower signals, smaller amplitude
- during early stages of slow-wave sleep and REM sleep
7
Q
K komplexes
A
IN STAGE 2
sudden sharp waves
only during stage 2 sleep
triggered by noises
8
Q
sleep spindles
A
IN STAGE 2
short bursts of waves (2-5 times a minute)
9
Q
delta activity
A
IN STAGE 3,4(3)
-high amplitude, low frequency
10
Q
wakefullness stage
A
- alpha activity
- beta activity
11
Q
Stage 1 sleep
A
(NREM1)
- transition between sleep and wakefulness
- theta activity
- vertex spikes
- Eyelids from time to time slowly open and close and eyes roll up and down
12
Q
theta activity in stage 1
A
firing of neurons is becoming more synchronised, slower signals, smaller amplitude
13
Q
vertex spikes
A
sharp waves
14
Q
Stage 2 sleep
A
(NREM2)
- higher amplitude, lower frequency
- sleep spindles
- k komplexes
15
Q
Stage 3/4
A
(NREM3)
- slow wave sleep
- delta activity
- down state (inhibition period: resting)
- up state (exhibition period)
- Only loud noises wake one up, then confused
- dreams ( nightmares)
16
Q
REM SLEEP
A
- EEG desynchronised, high frequency theta and beta activity
- EMG becomes silent -> loss of muscle tone -> paralysed
- Most of spinal -, cranial motor neurons strongly inhibited
- Don’t react to noises but meaningful stimuli such as name
- Brain very active (dreaming)
- Cerebral blood flow and oxygen consumption increase
17
Q
Activation-synthesis hypothesis
A
signals supplied to cortex are random and the cortex tries to make sense of it
18
Q
Sleep cycle
A
- Each cycle about 90 minutes long
- 20-30 mins of REM-sleep
- Most slow wave sleep in first half then more and more stage 2
- most REM sleep in second half
19
Q
Adenosin
A
- control of sleep
- Wakefulness decreases glycogen levels
- > causes an increase in extracellular adenosine levels
- > inhibitory effect on neural activity
- serves as sleep-promoting substance
- Caffeine blocks adenosine receptors
- Less adenosine less SWS
20
Q
Acetylcholine
A
= role in arousal
-High ACh levels during waking and REM-sleep, low during SWS
21
Q
Norepinephrine
A
- LC (locus coeruleus) neurons increase attention
- Firing high during wakefulness, low during SWS, almost zero during REM
22
Q
Serotonin (5-HT)
A
- role in activating behaviour
- Stimulation causes cortical arousal
- Facilitation of continuous automatic movements (chewing, pacing,… )
- Supressing processing of sensory information, precenting reactions that might disrupt ongoing activity
23
Q
Histamine
A
= role in arousal
-High during waking, low during sleeping
24
Q
Orexin/hypocretin
A
- cell bodies located in lateral hypothalamus
- Most active during active waking, exploratory activity
25
Recuperation theory
= being awake disrupts homeostasis (internal physiological stability) and sleep is required to restore it
-Restore energy levels or clear toxins
Why?
pro: animals sleep even when it endangers them
26
adaption theories
= sleep result of internal 24-hour timing mechanism
- Programmed to sleep at night regardless of what happens during the day
- Highly motivated to engage in sleep but don’t need it to stay healthy
27
niche adaption
=forces individual to conform to a particular ecological niche for which it is well adapted
28
Memory consolidation
So something about sleep must help brain to retain and form synapses
-Although necessary for survival – not necessarily needed in large quantities
29
Zeitgeber
daily cycle of light and dark entrains (controls timing of) circadian rhythms
30
Free-running rhythms
= reticular activating system
- Duration = free running period = relatively constant around 24.2 hrs
- Internal biological clock that is running a little late without external cues
- Support for circadian factors over recuperative factors in regulation of sleep
- Don’t have to be learned
31
Reticular formation
= reticular activating system
- Wakefulness
- Cycle disrupted when lesion to reticular formation core of brain stem, electrical stimulation awakens
- Low levels of activity: sleep
- High levels of activity: wakefulness
32
Reticular REM-Sleep nuclei
= REM sleep controlled by nuclei scattered throughout the caudal reticular formation
-REM becomes active when network of independent structures becomes active together
33
Pons
sends signals that shut off neurons in the spinal cord, causing temporary paralysis of limb muscles
34
hypothalamus
= switch between REM,NREM and wakefulness
| -Hypocretin prevents transition from wakefulness directly into REM
35
Basal forebrain
- promotes sleep and wakefulness
| - release of adenosine from cells in the basal forebrain and other regions supports our sleep drive
36
SCN ( Suprachiasmatic nucleus)
Clusters of thousands of cells that receive information about light exposure directly from the eyes and control our behavioral / circadian rhythm
37
pineal gland
It receives signals from the SCN and increases the production of melatonin (helps us sleep)
38
Insomnia
= difficulty falling asleep (sleep-onset) or staying asleep (sleep-maintenance)
- Sleep-stage misperception: think we weren’t asleep even though we were
- Situational factors like shift work contribute
- Nearly everybody (especially those who snore) have it occasionally but not to the extent that it interferes with sleep
- During an episode: level of CO2 in blood rises and stimulates chemoreceptors -> wake up gasping for air
39
sleep apnea
unable to sleep and breathe at the same time
40
Narcolepsy
= sleep attacks
- Enter REM-Sleep right away
- inappropriate activation of the cataplexy pathway normally restricted to REM sleep
- When strong emotional reactions (laughter & anger) sudden physical effort
41
Cataplexy
varying amounts of muscle weakness up to paralysis while being conscious
42
Hypnagogic hallucinations
person dreams while lying awake, paralysed
43
REM behaviour disorder (RBD)
| =
acting out of dreams during REM-sleep
- Motor cortex very active but normally motor neurons inhibited
- Damage to nucleus magnocellularis which controls muscle relaxation during REM sleep
44
REM-Sleep deprivation
- The longer the deprivation the more often initiation of REM sleep (had to be woken up more often)
- Default theory: difficult for brain to stay in NREM sleep so periodically changes to one of the other states
- If immediate bodily needs: switch to wakefulness, if not REM
- REM functions to prepare body for waking
45
REM rebound
more REM sleep the first few nights after deprivation
46
Sleep deprivation increases the efficiency of sleep
- deprived have higher proportion of slow wave sleep that seems to serve as main restorative function
- Regain only small proportion of sleep but most of SWS
- Less sleep – same amount of SWS
- Waking up from SWS has major effect on sleepiness the next day
47
hypnotic drugs like Benzodiazepines
-increase sleep
| GABA agonists
48
Anti-hypnotic drugs
reduce sleep
