Problem 7 – Night, night
Stages of Sleep
- physiological measures of sleep:
• major changes in the EEG during the course of a night’s sleep
- the EEG makes it possible to monitor brain activity during sleep
- first-night phenomenon: disturbance of sleep observed during the first night in a sleep laboratory
4 Stages of Sleep
1. NREM 1
• initial stage of sleep
• non-REM sleep
• low-voltage high-frequency
→ similar to the signal during alert wakefulness stages but slower
- as a person progresses from stage 1 sleep through stages 2 and 3: gradual increase in EEG voltage
and a decrease in EEG frequency
2. NREM 2
• slightly higher amplitude and lower frequency (than in stage one)
• is in addition punctuated by two characteristic wave forms:
1. K complexes
→ sharp waves
→ is a large negative wave (upward deflection) followed immediately by a single large
positive wave (downward deflection)
→ is associated with temporary inhibition of neuronal firing
2. sleep spindles
→ is a 0.5 to 3 second waxing and waning burst of 9 to 15 Hz waves
→ result from oscillating interactions between cells in the thalamus and the cortex
→ increase in number after new learning
→ the number of sleep spindles correlates positively with improvements in certain types
of memory
, 3. NREM 3
• also referred to a slow-wave sleep (SWS)
• is defined by a predominance of delta waves
• delta waves: the largest and slowest EEG waves with a frequency of 1 to 2 Hz
• heart rate, breathing rate, and brain activity decreases
• slow waves indicate that neuronal activity is highly synchronize
• once sleepers have reached stage 3 EEG sleep they stay there for a time
→ and then they retreat back to through the stages of sleep to stage 1 (emergent stage 1)
4. REM / Emergent stage 1
• once a person has returned back to stage 1 it is characterized by different characteristics
• is accomponied by REMs and by a loss of tone in the muscles of the body core
• rapid eye movements (REMs) occur under the closed eyelids of sleepers during the periods
of low voltages
Physiological characteristics of REM sleep
• REM
• loss of core muscle tone
• a low amplitude, high frequency EEG
• cerebral activity
• general increase in the variability of autonomic nervous system activity
• the muscles of the extremities occasionally twitch
• almost always some degree of penile or clitoral erection
- after the first cycle of sleep EEG of going to stage 3 and back to stage 1 – the rest of the night is
spend by going back and fourth through the stages
- the cycle is about 90 minutes long
- during a night more time is spend in stage 1 than in any other stage
- there are also brief periods during the night in which a person is awake but they usually don’t
remember
Dreaming
- evidence suggested that all REM sleep episodes were emotion-charged
- REM NREM and dreams:
• dream recalls from NREM sleep tend to be isolated experiences (“I was falling”)
• dream recalls from REM sleep tend to take the form of stories or narratives
• dreaming is much more prevalent during NREM than first assumed
→ NREM dreams are comparable to REM dreams
- activation-synthesis hypothesis:
• a dream represents the brain’s effort to make sense of sparse and distorted information
• information supplied to cerebral cortex is largely random during REM sleep
• resulting dream is the cortex’s effort to make sense of these random signals
Stages of Sleep
- physiological measures of sleep:
• major changes in the EEG during the course of a night’s sleep
- the EEG makes it possible to monitor brain activity during sleep
- first-night phenomenon: disturbance of sleep observed during the first night in a sleep laboratory
4 Stages of Sleep
1. NREM 1
• initial stage of sleep
• non-REM sleep
• low-voltage high-frequency
→ similar to the signal during alert wakefulness stages but slower
- as a person progresses from stage 1 sleep through stages 2 and 3: gradual increase in EEG voltage
and a decrease in EEG frequency
2. NREM 2
• slightly higher amplitude and lower frequency (than in stage one)
• is in addition punctuated by two characteristic wave forms:
1. K complexes
→ sharp waves
→ is a large negative wave (upward deflection) followed immediately by a single large
positive wave (downward deflection)
→ is associated with temporary inhibition of neuronal firing
2. sleep spindles
→ is a 0.5 to 3 second waxing and waning burst of 9 to 15 Hz waves
→ result from oscillating interactions between cells in the thalamus and the cortex
→ increase in number after new learning
→ the number of sleep spindles correlates positively with improvements in certain types
of memory
, 3. NREM 3
• also referred to a slow-wave sleep (SWS)
• is defined by a predominance of delta waves
• delta waves: the largest and slowest EEG waves with a frequency of 1 to 2 Hz
• heart rate, breathing rate, and brain activity decreases
• slow waves indicate that neuronal activity is highly synchronize
• once sleepers have reached stage 3 EEG sleep they stay there for a time
→ and then they retreat back to through the stages of sleep to stage 1 (emergent stage 1)
4. REM / Emergent stage 1
• once a person has returned back to stage 1 it is characterized by different characteristics
• is accomponied by REMs and by a loss of tone in the muscles of the body core
• rapid eye movements (REMs) occur under the closed eyelids of sleepers during the periods
of low voltages
Physiological characteristics of REM sleep
• REM
• loss of core muscle tone
• a low amplitude, high frequency EEG
• cerebral activity
• general increase in the variability of autonomic nervous system activity
• the muscles of the extremities occasionally twitch
• almost always some degree of penile or clitoral erection
- after the first cycle of sleep EEG of going to stage 3 and back to stage 1 – the rest of the night is
spend by going back and fourth through the stages
- the cycle is about 90 minutes long
- during a night more time is spend in stage 1 than in any other stage
- there are also brief periods during the night in which a person is awake but they usually don’t
remember
Dreaming
- evidence suggested that all REM sleep episodes were emotion-charged
- REM NREM and dreams:
• dream recalls from NREM sleep tend to be isolated experiences (“I was falling”)
• dream recalls from REM sleep tend to take the form of stories or narratives
• dreaming is much more prevalent during NREM than first assumed
→ NREM dreams are comparable to REM dreams
- activation-synthesis hypothesis:
• a dream represents the brain’s effort to make sense of sparse and distorted information
• information supplied to cerebral cortex is largely random during REM sleep
• resulting dream is the cortex’s effort to make sense of these random signals
