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8 Sleep loss, performance (Circadian rhythm (Dijk (Influence on stages…
8 Sleep loss, performance
Circadian rhythm
The 2 process model of sleep regulation
Borbely
2 different processes
S
Sleep dependent
Exponential decline during sleep and increase during waking
Sleep deprivation only leads to small increase in sleep time
Function of prior waking time
Linked with SWS
Enhanced after sleep deprivation
adenosine
C
Circadian dependent
Rhythmic variation
Controlled by circadian oscillator
Linked with REM
Increases across successive NREM-REM cycles
Remains elevated several nights after (severe) deprivation
Body temperature
Related to vigilance
24h cycle
Sleep propensity highest at minimum, lowest at maximum
Sleep propensity
S+C
Dijk
Sleep cycle
90 min
Circadian rhythm
unentrained
External desynchony
still sleep wake cycle but independent of 24h day
4 to 6 h later
Dependent on multiple oscillators
Become desynchonized without entrainment
Pacemaker
Located in SCN
Drives melatonin and cortisol rhythm
Homeostat
?
Hourglass oscillator
Diffuse system but not SCN
Model
Social factors
Having to wake up
lower performance at night
decrease in performance with sleep deprivation
Performance declines in the afternoon
Influence on stages
REM
S+C
SWS
S
Sleep spindles
C
Sleep and performance
Shift work
Akestedt
Measuring sleepiness
Subjective
Karolinska Sleepiness Scale
1 very alert - 9 very sleepy (effort to remain awake)
Physiological
EEG/EOG
Recognizes around level 7 of subjective
Alpha and theta incresed
more slow eye movement
Accidents
No explicit link between sleepiness and risk
Reduction of work hours leads to reduction of accidents
30-40% of truck accidents fatigue related
Most at 9 on KSS scale
Hit reduces EEG but only for a few minutes
Causes of sleepiness
Work falls together with window of circadian low
Subsequent sleep with circadian rise
Sleep loss is taken out of stage 2 and REM
Three process model of alertness
Types of shifts
slow? counterclockwise rotations worst for sleep
Shift work disorder
in 10%
Effects of caffeine and alcohol
Alcohol
Daweson
Compared sleep deprivation with alcohol intake
Condition 1
Awake fore 28 hours
Condition 2
Blood alcohol concentration of 0,1%
Task
Hand-eye coordination test
Results
Performance decreased in both contitions
Effects of moderate sleep loss on performance are similare to moderate alcohol intoxication
decrement for each hour of wakefullness between 10 and 26 hours was ecquivalent of alcohol rise of 0.004%
After 24h similar to 0.1%
Caffeine
Lorist
Function
Blocks adenosine receptors
Linked to dopamnine
Increase transmission via D2
Dopamine linked to fatigue
Process S
Effects
Inverted U shape dose-response
Attentional system
General positive effect
Does not facilitete automatic attentional processes
improved preparation/motor response io attention
Different findings
EEG
more arousal
counteracted effect of sleep loss
Increased receptivity of external stimuli and accelerates perceptual processing
More effect when attentional control is reduced