EEG and sleep Flashcards
zeitgebers
environmental timing cues that affect circadian rhythm e.g. sunlight
endogenous
from within
periodicity of circandian rhythm
24hours
where is suprachiasmatic nucleus
in the anterior hypothalamus
what does suprachiasmatic nucleus do
regulates timing of sleep
not sleep itself
day light has lots of which wavelength
blue wavelength (which helps us wake up)
melatonin
sleep hormone
naturally accumulates as day goes on, and by evening you are tired
sleep defined as
reduced motor activity
reduced response to stimulation
stereotypic postures (eyes closed in humans)
relatively easy reversibility
electromyography
electrical activity of muscles
extrooculuography
elextrical activity from the eyes
EEG measures
synchronous electrical activity from LARGE populations of neurones in the brain
caused by cellular ionic movement, which creates an electric field
each scalp electrode of EEG
is the summation of many millions of neurones all of a similar spatial orientation
pros/cons of EEG
non invasive easy to administer data easily gathered high temporal resolution (event generated potentials)
low spatial resolution
electric fields follow an inverse square law so only cortical activity detectable (smaller the further distance away- so the surface cortex can only be recorded)
non REM sleep
characterisitcs
neuronal activity is low
not music action potential firing between neurones
metabolic rate and brain temperature at their lowest
heart rate and blood pressure decline (decreased sympathetic nervous system outflow)
increase in parasympathetic outflow dominates no REM sleep- constricted pupils
muscles tone and reflexes still in tact e.g. knee jerk
stage 1 sleep
drowsiness
awakened easily
eyes move slowly and muscle activity slows
sudden muscles contractions preceded by a sensation of falling
transitions from wakefulness to onset of sleep- several minutes
EEG activity for awake people
low voltage (10-30μV@16-25Hz)
as they relax- sinusoidal (alpha) activity 20-40μV@10Hz
activity of mixed frequencies
EOG of stage one
eyes show slow, rolling movements
EMG of stage one
some muscular activity
stage 2
light sleep
eye movement STOPS
and brain waves become slower with only occasional burst of activity
the body temp drops, heart rate slows
stage 2 EEG
characterised by bursts of sinusoidal waves called ‘sleep singles’ (12-14 Hz) and biphasic waves called K complexes
biphasic
up and down relative to baseline
k complexes
occur episodically against background of continuing low-voltage EEG activity
stage 3
deep sleep
extremely slow delta waves, interspersed with smaller, faster waves
sleep walking, night terrors, talking, bedwetting ‘parasomnia’
occur during the transitions between non REM and REM sleep
FUGE state- disorientation, hallucination, irritability
stage 3 EEG
high amplitude, slow delta waves (0.5-2Hz)
stage 4
very deep sleep
brain shows delta waves almost exclusively
disorientation for several mins following arousal from this stage
stage 5
REM sleep
EEG mimics wakefulness
closed eyes move rapidly from side to side
low voltage mixed frequency
‘paradoxical sleep’
stage 5
Neurones in Pons of brainstem, lateral geniculate nucleus and occipital cortex
neurons in pons of brainstem,
lateral geniculate nucleus
and occipital cortex fire in more intones burst during REM that in wakefulness
intense firing generates high voltage spike potentials in EEG called
ponto-geniculo-occipital spikes
PGO
PGO type spikes can be produced in alert subjects by startling them with an abrupt stimuli like a loud noise
suggesting..
PGO of REM sleep may be activated by the same neural circuits that initiate the ‘startle response’
PGO are also correlated with bursts of eye movements in REM sleep
during REM sleep
brain temp and metabolic rate rise
- consistent with increased neural activity
in some areas- greater than in walking!
all skeletal muscles are atonic
muslces controlling movements of eyes, middle ear ossicles, and diaphragm remain active (so you can breathe and hear impeding danger!)
penile erections in men
clitoral engorgement in women (controlled by parasympathetic nervous system)
pupils highly constricted (mitosis)
respiration is unrespeosive to change on blood pCO2
responses to heat and cold reduced or even absent- body temp drifts toward ambient
atonic
flaccid and paralysed
so why is sleep not a continuum from light to deep sleep
Each phase is behaviourally complex and reflects the physiological
mechanisms representing a distinctive brain state
REM could be said to be a lighter sleep since arousal is easier than in stages 3-4
Non-REM could be said to be lighter sleep because body temp, muscle tone and
reflexes are all maintained.
normal human sleeping patterns
After 70-80 minutes sleeper returns to stages 3 or even 2 before entering first
REM phase of the night which lasts 8-10 minutes.
Time from first stage to end of REM = 90-110minutes
Repeated four or five times per night-during each repetition, stages 3 & 4
decrease in duration and REM increases
in young adults what percentage of sleep spent in stage 1
only 5%
in young adults, the largest amount of sleep occurs in what stage?
50-60%
what percentage of sleep in young adults is 3-4 stages
15-20%
REM phases of sleep constitute what percentage in young adults
20-25%
theories of dreaming
strange-imagery brain not fully functioning
exerceises synapses when no external activity
memory consolidation
circuit testing
