6.3 Waking and Sleeping (각성과 수면)



Circadian Periodicity as the Basis of the Waking/Sleeping Rhythm
The circadian oscillator
Protozoans---> Humans: rhythmical changes
rhythm coupled with 24 hour periodicity
earth rotation, tides, phases of the moon
annual cycle

passive vs active rhythmicity
---> free-running rhythm (shorter or longer than 24 hr)
---> biological clock (endogenous processes)
---> circadian rhythm (self-excited oscillator)
---> synchronized with 24-h cycle by external entraining signals

Circadian periodicity in humans
more than 100 parameters: changes cyclically with a 24 h period
body temperature: early morning <1-1.5oC evening
waking/sleeping cycle
considerable number of circadian oscillators of somewhat diff. periods

free-running rhythm (bunkers or caves): Fig. 6-15
A: 24.0+-0.7 h ---> 26.1+-0.5 h somewhat longer
body temp. maxim: just before the onset of sleep
2 day after: phase shift: couple and decouple
B: extreme case: 48 h, bicardian rhythms
complete uncouple: autonomic body temp> 25.1 hr vs. 33.4 s/w
temperature clock is less flexible

flight (jet lag): to east---> shorthen
to west---> lengthened(phase delay), easier reentrainment
1 day/time zone: 1 h shift
body temperature: slowly reentrained

ratio of the duration of activity and rest times within a circadian cycle is not kept constant
---> average circadian period is kept as constant as possible---> circadian periodicity is the primary process
---> sleeping and waking are subordinate
side effects of endogenous circadian periodicity

significance of the circadian rhythms:
inherited
phylogenetic adaptation to the temporal structure of our environmental events
internal copy of the schedule of environmental events
---> organism can adjust itself in advance to the changes
in environmental conditions to be expected at any time
---> performing certain actions at suitable times of the day
---> measuring time by means of the internal clock

pacemakers for the circadian rhythm:
in CNS
1. suprachiasmatic nucleus (SCN) in the ventral hypothalamus
---> regulating the activity cycle (S/W rhythm)
: input from the visual system
: synchronized with the VMH by close reciprocal connections

2. ventromedial nucleus of the hypothalamus (VMH)
---> temperature & feeding rhythm (glucose, corticoid level)

Phenomenology of Waking and Sleeping

Human waking/sleeping behavior
Neither waking nor sleeping is a homogeneous state of consciousness
수면은 단순한 무활동의 시기라기 보다는 일련의 연속적 상태
Stages of sleep: depth of sleep <--- intensity of a stimulus sufficient for
awakening
EEG (뇌전위) pattern: Fig. 6-16

Stage W: Waking: alpha waves (8-13 Hz), 뇌의 뒷부분에서 현저
Stage A: alpha waves ---> disintegrate, small theta waves (4-7 Hz)
transition from waking to sleeping
Stage B(1): lightest level of sleep, 제 1 단계 수면
theta waves
at the end of stage B---> large vertex sharp waves (3-5 sec dur)
심장박동률 감소, 근육 긴장 감소
Stage C(2): light sleep
beta spindles (sleep spindles), K complex

외적 자극에 대해 거의 무반응
Stage D(3): intermediate sleep
rapid delta waves (3.0-3.5 Hz)
Stage E(4): deep sleep, EEG is synchornized, 큰 진폭
maximally slowed delta waves (0.7-1.2 Hz), occaisonal alpha
Stage BCDE= NREM sleep, synchronized sleep, slow wave sleep (서파수면)

REM stage
desynchonized waves, resembling stage B
burst of rapid eye movement (급속한 안구운동), 각성시키기 매우 힘듬
---> by naked eye, electro-oculogram (EOG)
rest of the musculature is practically atonic (근육이완)
bursts of brief twitches, 호흡, 심장박동 빠름
awakening threshold is about as high in REM sleep as in deep sleep
paradoxical sleep (역설적 수면), desynchonized sleep
dream occurs during REM sleep

Fig. 6-17:
a: 3-5 cycles/night, REM stage recur about every 1.5 hrs,
평균 1.5 시간의 cycle: 기본 휴식활동 주기 (basic rest-activity cycle)
각성중의 공상(daydreaming)도 약 100분 간격

duration average 20 min, increases in the course of the night
(처음 REM 기간은 불과 5-10 분, 깨어나기 직전: 40 분 정도 지속)
수면 초기의 주기들은 짧고, 3,4 단계의 서파수면이 많다.
body temperature: unaffected by the rhythmic fluctuations in depth of sleep
e: heart rate, respiration: phasic fluctuations, pennis errection
especially apparent during REM sleep.

Fig. 6-18:
Age relation
reduction in total sleeping time, 모든 포유동물에서 생후 2주 까지: 50%가 REM 수면, 각성상태에서 바로 REM으로 이행가능
생후 16 주가되면 수면과 각성의 주기가 명백해진다.
decrease in the proportion of REM sleep
large proportion of REM sleep in very young children---> importnat for the ontogenetic development of the CNS
짧은 평균시간, 빈번한 S/W cycle
5-6세 까지는 slow wave 수면의 특징적인 EEG이 불명확노인: 3,4 단계 수면의 감소: 인지능력의 감소와 유관

Sleep and dreams

dream: NREM < REM
60-90% dream reports on waking from REM sleep
NREM: talking, sleepwalking, night terror of children, abstract, thought-like (cognitive), 사고적
REM : more lively, visual, and emotional, sensory (odrors, tones), easier to recall
by no means a consequence of visual dream (unborn, newborn)

first half of the night: more closely related to reality
having to do with events of the preceding day, 현실적 내용이 중심

second half of the night: less related to every day life, toward morning, bizarre, emotionally intense

Preceding events influences dreams
water deprivation--->
exciting movie or TV play before going to bed--->
increases duration and intensity of the REM phases and the dreams

REM deprivation---> longer and deeper REM, more intense dream
---> no long-lasting physical or mental consequences
External stimuli during REM sleep
acoustic stimuli---> incorporated into dreams
time markers for the dream reports

Sleep, dream and memory
꿈의 기능: 수수께끼, 원시 문화 (꿈의 진실성 강조), 문제해결, 소원성취, 무기능
not retained unless alpha activity appears in the EEG during or after the presentation
final dream before awaking is remembered.










BRAIN FACTS

Sleeping facilitates the consolidation of material to be learned
several possible reasons
a: less distracting events (방해자극의 감소)
b: passive forgeting process operates more slowly
c: active REM sleep makes a positive contribution

Sleep disorders
snoring: mouth open, tongue sunk back into the throat, supine
sleep apnea (수면성 무호흡): spontaneous interruption of breating
crib death (유아가 갑자기 죽는 증후)
grinding of the teeth: teeth sharpening, phylogenetically old
talking in one's sleep

Sleepwalking (somnambulism, 몽유병)
neither pathological symptom nor harmful
happen to at any age, but is most common in children and young
occurs in deep sleep
서파수면시(3,4단계 수면)에 많다, 성숙해지면서 사라짐

Bed-wetting (enuresis)
happens to about 10% of all children above the age of two
always occurs during NREM sleep
밤수면의 처음 1/3에 주로 (3,4단계 수면시)

Pavor nocturnus (night terror)
3-8 years old, rare after puberty, 비명
잠든지 약 1시간후에 나타남, 제4단계 수면시 주로

Sleep paralysis
absolutely impossible to make a movement
when waking up, falling asleep, fully conscious
suprising, often accompanied by frightening halucinations

Insomnia
수면의 시작과 지속의 장애
about 15% of all adults
subjective sleep deficiency
actually sleep more than they realize
as long as the insomnia does not involve distinct shortening
of total sleep duration for a long period---> no threat to health
정상인에 비해 더 적은 REM 수면, 더 많은 2 단계 수면

수면발작 (narcolepsy):
갑작스런 수면, 5-30분간 지속 (정상적인 일과 중에도)
근육긴장의 일시적 상실, 막바로 REM 출현, 뇌간의 기능장애, 강한 정서자극에 의해

위궤양 환자: REM시 3-20배 위산 분비
심장병 환자: 사먕, 새벽 4-6시 (REM이 가장 강하고 지속적일때)

Waking/sleeping behavior of animals
REM sleep is a relatively recent development.
Fish(어류), 양서류, reptiles: no REM sleep
Birds: very brief (seconds), less than 1 %
검은 제비갈매기: 활강중에 잠간 잠, 착륙하지않고 몇달 공중
Mammals: considerable time for REM sleep
hunting species: about 20%
hunted : 5-10%
몸집이 작은 소동물: 짧은 REM 기간, 짧은 수면 주기
(REM 수면: 체온 조절 불확실)

Mechanisms of Waking and Sleeping

1) Why must we sleep?
2) How does sleep begin?
3) Why and how does it end?
4) What mechansims are responsible for the various stages of sleep and for the periodic transition from one stage to another?

A: conesquence of a decrease in wakefulness
passive envent
B: active termination of the waking state

Deafferentation theory of sleep
Fig. 6-19
1930, F. Bremer, EEG of cat brain
isolated brain (lesion at medulla)---> synchonized & desynchronized waking patterns
isolated forebrain (lesion at midbrain)--->elimination of all sensory stimuli except sight and smell---> only a synchronized sleeping EEG

conclusion:
1) activity of the CNS is induced and controlled primarily by sensory stimuli.
2) waking state requires at least some minimal level of cortical activity, maintained by sensory input
3) sleep is a condition induced and maintained by a reduction or diminished effectiveness of sensory input. Deafferentation
4) sleep induction is basically a passive phenomenon.

Opposition to deafferentaion theory:
1) in time the chronic isolated forebrain prepearation does develp a sleeping/waking rhythm.
2) sensory deprivation causes a progressive decrease in the duration of sleep during the period of isolation
3) organisms without the tel- and diencephalon show sleeping/waking rhythm.

Reticular theory of waking and sleeping

Fig. 6-19C
late 1940's, G. Moruzzi and H.W. Magoun
brainstem reticular formation (RF): 뇌간의 망상체
high frequency stimulation---> immediate awakening
lesion---> permanent sleep
ARAS (ascending reticular activating system)
nonspecific projections
crucial arousal center

Opposition:
1) electrical stimulation---> both sleeping and arousal
2) neuronal activity: no correlation
3) isolated forebrain---> S/W rhythm
RF not soley responsible for waking and sleeping

Serotonergic theory of sleep

Fig. 6-19C
raphe nuclei: serotonin (5-HT), M. Jouvet, late 1960's
cat, destruction of the raphe nuclei---> total insomina for several days
blocking the synthesis of 5-HT (with parachlorophenylalanine, PCPA)--->partial loss of sleep
5-hydroxytryptophan (precursor of serotonin) 투여---> correction

locus coeruleus (noradrenalin)
bilateral destruction of LC---> complete abolition of REM, but no effect on NREM
Reserpine 투여---> simultaneous exhaustion of the stores of serotonin and noradrenalin
---> insomnia
subsequent 투여 of 5-hydroxytryptophan---> restores NREM only

conclusion: 1) release of serotonin causes active inhibition of the the arousal systems---> induces sleep (NREM)
2) REM sleep by LC
3) LC inhibits raphe N---> initiation of awakening

this theory is no longer tenable in its original form
raphe neurons: most active in arousal rather than in sleep
REM activation seems to be due less to the neurons of the LC than to those of the more diffusely distributed nucleus subcoeruleus
but 5-HT: promoting the synthesis or release of sleep substances

Endogenous sleep factors
1) sleep factor(s) would accumulate during the waking state
Factor S (a small glucopeptide from urine or cerebrospinal fluid)---> induces NREM sleep
REM-sleep factor
2) sleep promoting substances are produced or released during sleep
DSIP (delta sleep inducing peptide, nonapeptide)

not known what role they play in the physiological control of sleep

Biological functions of sleep (수면의 생물학적 기능)

증명된것 무
no satisfactory answer to the question of why we must sleep
1) Serving recovery: little experimental support
a) physical exertion ---> causes to fall asleep
no change of the duration of sleep
수면전 신체운동--> 전체 수면시간의 무변동
b) people with extremely little sleep
말: 2 시간/하루,
standford 대의 한 교수: 50년 이상 3-4 시간/하루 ---80세
c) no explanation for the existence of REM and NREM sleep
2) 에너지 보존: 수면시 에너지 소비감소
(근육긴장, 심장박동, 혈압, 호흡, 신진대사등의 감소)
문제점: REM sleep
3) 포획동물로 부터의 회피: 생태적인 적소에서, REM 수면은 주기적 유사각성
4) 정보처리를 도운다: 하루동안의 기억을 분류하고 강화하는 기능










BRAIN FACTS