Transcript Day and Night

Psychophysiology of day/night cycle
Netania 2003-04
Interesting site:
http://www.sleepfoundation.
org/publications/letsleepwork.cfm#1
We change with time
What is changing ?
Linear changes ?
Cyclic changes ?
Source of changes?
Exogenous clocks: Environment as a source
of cyclic changes
Environment is cyclic… we are sensitive to
environment, therefore…. we live in cycles.
“The Calendar” describes life timed by nature.
 365 + 1/4 days around the sun: cycles of
depression, suicide, susceptibility to
schizophrenia…
 28-31 days: Gregorian timing in honor of
Caesar? No environmental cycle.
 1 day spin: light/dark cycle of biological &
mental functions.
Endogenous clocks: Biology as
a source of cyclic changes
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Annual clock: not known.
Monthly clock: female menstrual cycle.
Circadian clock: > 24 hrs, why not = 24 hrs?
8 hrs clock: when the pilots are most fit?
90 min clock: when do you dream?
< seconds range: localized biological
processes like sand clocks, HR,
biochemistry.
Chronobiology research is being conducted by:
• Allergists
• Animal and plant
physiologists
• Cardiologists
• Cell and molecular
biologists
• Chronobiologists
• Endocrinologists
• Environmental scientists
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Gastroenterologists
Immunologists
Nephrologists
Neuroscientists
Obstetricians/gynecologists
Pharmaceutical scientists
Psychiatrists
Toxicologists
Epidemiologists
Do you see the psychologists ???
Complex cycles: Interaction between
exogenous & endogenous clocks
 Monthly: Synchronization of monthly cycle
in ladies’ dormitories.
 Circadian: > 24 hrs in isolation, but 24 hrs in
normal conditions.
 90 min: easy to detect in boring but not in
exciting conditions.
Complex cycles: 24 + 8 cycles in phase
24 hrs
8 hrs
result
Complex cycles: 24 + 8 out of phase
24 hrs
8 hrs
result
Cyclic changes: conclusions
Continuous change rather than stability
Change in response to exogenous clocks
Change in response to endogenous clocks
Asynchronous cycles
Models of adaptation (e.g., arousal)
Models of pathology??? (e.g., arousal)
Sleep (2)
External clock:
Light through eyes & skin
Biological clock:
Suprachiasmatic n.
Pineal Gland (melatonin)
Spectrum of Arousal
Coma
Sleep - Wakefulness
Excitation - Anxiety
Drugs
Epilepsy
Circadian cycles of arousal
Momentary changes of arousal
Arousal and Performance
Arousal is a major aspect of behavior and is closely
related to other concepts such as anxiety,
attention, agitation, stress, and motivation.
The arousal level can be thought of as how much
capacity you have available to work with.
One finding with respect to arousal is the YerkesDodson law which predicts an inverted U-shaped
function between arousal and performance.
Arousal and Homeostasis
Homeostasis:
Maintaining a
single level of
adaptive
arousal
Arousal and Allostasis
Allostasis
rather than
homeostasis:
Stable level of
arousal is not
adaptive
Allostasis and Performance
Allostasis: maintaining stability of
performance through change of arousal, as a
fundamental process by which organisms
actively adjust to both predictable and
unpredictable events.
i.e., stay maximally adaptive by changing the
arousal
Allostatic overload being a state in which
serious pathophysiology can occur.
Allostasis and Poor Performance
Allostasis:
Catastrophic
conditions are
possible
Alertness daily cycle
Sleep Needs over the Life Cycle
Toddlers/Children 1-1.5 yrs: 13-15 hours
1.5-3 yrs: 12-14 hours
3-5 yrs: 11-13 hours
5-12 yrs: 9-11 hours
Adolescents
8.5-9.5 hours
Adults/Older Persons
7-9 hours
Sleep Needs over the Life Cycle
Circadian sleep distribution
Sleep cycles and stages
Sleep like wakefulness, is not homogenous.
Sleep cycles and stages (again)
Sleep stages
NREM: 75% of night sleep; composed of Stages 1-4.
Stage 1: Light sleep; between being awake and entering
sleep.
Stage 2: Becoming disengaged with the environment;
breathing and heart rate are regular and body temperature
goes down.
Stage 3 & 4: Deepest sleep; blood pressure drops; breathing
slower; energy regained; hormones are released.
REM: 25% of night sleep. 1st about 90 min after falling
asleep; length increases over the subsequent cycles;
cortex is active and dreams occur as eyes dart back and
forth; bodies become immobile and relaxed; muscles shut
down; breathing and heart rate may become irregular.
EEG in sleep
Beta: > 13 Hz
Alpha: 8-13 Hz
Theta: 4-8 Hz
Delta: < 4 Hz
EEG in sleep (3)
REM dream
The painting suggests
Delvaux was not
optimistic about either
approach, preferring to
celebrate rather than
resolve the central
mystery.
A dream and its investigators in
a painting by Paul Delvaux.
The dream
Neurologist examines…
Psychologist inquires…
Sleep & response
to environment
Overt – awakening
Covert – dream
Sleep & selective
attention
Sleep and learning
Sleep & Learning:
 Dawkins – “The
selfish gene”
 The song of Don
Juan
"The zebra finch appears to
store the neuronal firing
pattern of song production
during the day and reads it
out at night, rehearsing the
song, and, perhaps,
improvising variations. The
match is remarkably good."
Sleep functions: The genetic prospective
Molecular support for the concept that sleep is
implicated in synaptic plasticity and memory
(Mircea Steriade).
Circadian genes differentially expressed during day
and night.
For some of the above, upregulation is attributable to
sleep itself. Out of some 15,000 transcripts present
in rat cerebral cortex, about 10% (1,564) were
differentially expressed by day or night. For about
half of these (752), the change was attributable to
the waking or sleeping state, independent of time.
The body sleeps, but the genes do not.
“Sleep genes” are upregulated specifically during sleep and
suggest the following sleep's functions:
 genes involved in synaptic plasticity, memory
consolidation.
 genes underlying translation, supporting observations
that protein synthesis increases during sleep.
 genes regulating membrane, vesicle trafficking, vesicle
recycling, exocytosis, docking of vesicles &
neurotransmitter release.
 genes for synthesizing cholesterol, which may be crucial
for synaptogenesis & membrane synthesis.
Cirelli et al., "Extensive and divergent effects of sleep and wakefulness on brain
gene expression," Neuron, 41:35-43, 2004.
SWS & REM builds memories
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Researchers recorded the electric signature of individual
forebrain neurons firing during the two types of sleep.
The firing pattern of recently captured memories are
especially strong during slow-wave sleep and then
decrease in force dramatically during REM.
The neural plasticity genes turn on during REM sleep.
It looks like a two-stage process: The memory echoes
strongly during SWS, which stabilizes it. Then the gene
expression machinery turns on during REM sleep to
further consolidate it.
You remember more when you have a combination of
REM and SWS.
Ribeiro et al., "Long-lasting novelty-induced neuronal reverberation during slow-wave
sleep in multiple forebrain areas," PLoS Biol, 2:0126-37, 2004.
Sleep deprivation
 sleep pressure
 no full compensation on recovery night
 intrusion of sleep to wakefulness
* compensation
* mixture of mental processes
* model of psychopathology ???
Sleep deprivation & driving
Getting less than 6 hours a night can affect coordination,
reaction time and judgment, in continuous performance
tasks, posing "a very serious risk.“
Drivers are especially vulnerable. Driving after 17 to 19
hrs of wakefulness is worse than after blood alcohol
level of 0.8% which is the critical level in US.
America is asleep at the wheel
The 2002 National Sleep Foundation (NSF)
Sleep in America poll revealed that one-half
of all American adult drivers—particularly
young males—admit to driving drowsy in
the past year, and almost one in five admit
to having fallen asleep behind the wheel.
The results are appalling, and unless
something is done, they may well get worse.
Sleep deprivation and hyperactivity
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Inadequate sleep makes kids more moody, more
impulsive, and less able to concentrate and learn (J. of
Exp. Psychology, 1975).
Recent research has verified that chronic poor sleep
results in daytime tiredness, difficulties with focused
attention, low threshold to express negative emotion
(irritability and easy frustration), and difficulty
modulating impulses and emotions (Seminars in
Pediatric Neurology, Mar 1996).
These are the same symptoms that can earn kids the
diagnosis of attention deficit hyperactivity disorder.
Flies bred lacking their cycle gene tended to die after
missing only 10 hours of sleep, found scientists
from the Neurosciences Institute in San Diego,
California.
Scientists noticed that other genes in these mutated
flies were less active after sleep deprivation.
These genes, which produce "heat shock" proteins,
were artificially stimulated prior to sleep
deprivation by raising the fly's environment to
human body temperature.
"These 'heat shock' proteins protect cells when they
are under stress.
"Perhaps, if you can turn on these proteins in
humans, it could be beneficial."
TIPS FOR GOOD SLEEP
• Avoid caffeine (coffee, tea, soft drinks, chocolate) and
nicotine (cigarettes, tobacco products) close to bedtime.
• Avoid alcohol as it can lead to disrupted sleep.
• Exercise regularly, but complete your workout at least 3
hours before bedtime.
• Establish a regular relaxing, not alerting, bedtime routine
(e.g. taking a bath or relaxing in a hot tub).
• Create a sleep-conducive environment that is dark, quiet
and preferably cool and comfortable.
Consciousness (1)
Consciousness
Subconciousness
Unconsciousness
Consciousness (2)
Visual pathway
Consciousness (3)
Reconstruction
of natural
scenes in
thalamus
Consciousness: Conclusions
Localization of consciousness:
Consciousness not in the subcortical areas
Consciousness not in the primary sensory
cortex
Consciousness in high cognitive cortex ???