Rhythms of Sleep Flashcards
Sleep Deprivation Studies: Humans
3-4 Hours Deprivation:
- Increased sleepiness
- Disturbances of mood
- Poor performance on tests of vigilance
2-3 Days of Continuous Deprivation:
- Experience microsleeps, naps of 2-3 seconds
Longer Periods of Deprivation:
- No effects on motor performance
- No effects of cognitive performance
- May affect creativity
- Correlated with dementia
Circadian Rhythm
Any biological process that displays endogenous, entrainable oscillation for an average of 24 hours
Ex. sleep cycle
Infradian Rhythm
A biological rhythm that lasts longer than 24 hours, but less than a year
Ex. Menstrual cycle
Ultradian Rhythm
A biological rhythm that occurs repeatedly throughout the day
Ex. Microsleeps, blinking
Zeitgebers
Environmental cues that entrain circadian cycles (light-dark tides)
- Without Zeitgebers, animals display “free-running
rhythms”
- Humans average around 25 hours
- The circadian clock is located in the suprachiasmatic
nucleus
- Even when isolated, it shows cycles of electrical,
metabolic, and biochemical activity
- The Retinohypothalamic tract connects the retina with
the SCN
- Photoreceptors that entrain the SCN are light-sensitive
ganglion cells
Suprachiasmatic Nucleus (SCN)
- Light information is sent directly to the SCN (in the hypothalamus)
- SCN: primarily biological clock, receiving projections from retinohypothalamic pathways
SCN Signaling of Pineal Gland
- SCN signals the pineal gland about light/dark phases
- Pineal gland secretes melatonin during dark phases
- Lesions of the SCN or pineal gland disrupt rhythms controlled by light/dark phases
- Create free-running circadian rhythms
- Abolish annual breeding cycles
Function of Melatonin
- Synthesized from serotonin in the pineal gland
- Melatonin is not a sleep aid
- Pineal gland is main source of melatonin
- just one pineal gland
Sleep Cycles
4 Stages:
1. Stage 1 (non-REM)
2. Stage 2 (non-REM)
3. Stage 3 (non-REM & slow-wave sleep)
4. REM
Stages Differ By
- Neural Activity
- Eye Movement
- Muscle Activity
Studying Sleep
Electro-oculogram (EOG): monitors eye movement
Electromyogram (EMG): measures muscle activity
Electroencephalogram ( EEG): measures brain waves
EEG Activity
- Delta
- Theta
- Alpha
- Beta
Wakefulness
Beta: irregular, low amplitude, typical of alertness & active
thinking
Alpha: regular, medium frequency, typical of resting
PGO Waves
- Distinctive patterns of high amplitude electrical potentials known as PGO waves
- Waves neural activity begins in the pons, followed by lateral geniculate nucleus of the thalamus, and then in the occipital cortex
- REM deprivation results in high density of PGO waves when allows to sleep normally
When Sleep Begins:
Stage 1: Alpha to Theta waves with vertex spikes;
transition from wakefulness to sleep
Stage 2: Theta waves continue, but now marked by sleep
spindles and k-complexes
Stage 3: Beginning of deep or slow wave sleep & involves a
combination of Theta and Delta
- The deep, restful sleep, where it’s hard to wake you up
- High amplitude, low frequency
REM Sleep & Dreaming
- External stimuli can be incorporated into dreams
- Dreams run on “real time”
- Virtually everyone dreams
- Sleepwalking, sleep talking, and bedwetting occur more frequently during SWS than during REM sleep, when core muscles are relaxed.
Lucid Dreaming
- Dreams in which the sleeper realizes they are in a dream
- Can be trained through intention setting before bed, as well as use of a different electronic devices
- Studies of this experience has allowed the understanding of the experience of time in dreams
Forebrain System (Basal Forebrain)
Generates SWS
Brainstem System
- Medulla, Pons, etc
- Reticular Activating System
Activates the forebrain to wakefulness
A Pontine System
Triggers REM sleep
Why Do We Sleep?
- Energy Conservation
- Niche Adaptation
- Restoration & Recovery
- Memory Consolidation
A Hypothalamic System
- Makes sure we keep a stable system
- Coordinates the other three
Dreaming To Forget
- REM sleep erases spurious associations between neurons before they can inappropriately trigger synaptic plasticity & learning
Reverse Hebbian Rule: weakens connections when a dream co-activates neighbouring neurons
- Weak associations are actively down-regulated by random input
Sleep Disorders in Children
- Night terrors & sleep enuresis (bed-wetting) are associated with SWS
- Somnambulism (sleep walking)
occurs during stage 3 SWS- May persist into adulthood
Freud Dream Theory
Believed dreams provide insight to the subconscious
- Dreams constitute a disguised
attempt at wish fulfillment
- Criticized because it cannot be
proven wrong
Activation-Synthesis Model
Theory that dreams have no meaning at all
- Represent random activity from
the brainstem that is sent to the
cortex
- Cortex “synthesizes” and
explanation, weaving a story
from random inputs
Sleep Paralysis
Brief inability to move just before falling asleep or just after waking
- The pontine center may be
continuing to impose muscle
paralysis after wakefulness
People with Narcolepsy
Have frequent, intense sleep attacks: SWS can be induced with over excitement
- Last 5-30 mins
- Occur any time of the day
- Occur several times a day; every
90 mins
Do not go through SWS before REM sleep
May show cataplexy - a sudden loss of muscle tone, leading to collapse
Sleep-Onset Insomnia
Difficulty in falling asleep and can be caused by situational factors, such as shift work or jet lag
Sleep-Maintenance Insomnia
Difficulty in staying asleep and may be caused by drugs or neurological and psychiatric factors
Sleep Apnea
Breathing may stop or slow down when muscles in the chest and diaphragm relax too much or from changes in the pacemaker respiratory neurons in the brainstem
Sleep-State Misperception
Occurs when people report they haven’t slept even when EEg indicates they have
REM Behavior Disorder
Organized behavior in a person who appears to be asleep
- Usually begins after age 50
- More common in men
- May be followed by early
symptoms of Parkinson’s
disease and dementia
- Suggests the widespread
damage of these diseases
begins in the brainstem region
that imposes muscle atonia
