test 1 Flashcards
how is deep sleep assessed?
how difficult it is to wake someone, the degree of EEG or behavioural responses to external stimuli, degree of drowsiness that follows waking,
Which features of REM sleep are categorized as tonic?
postural muscle paralysis, low-voltage cortical EEG, loss of temperature control
Which features of REM sleep are categorized as phasic?
rapid eye movements, peripheral muscle twitches
The major contributors to mammalian EEG recordings are postsynaptic potential occurring in large ______________ neurons with somata located in layer ____ of the 6-layered cortex.
pyramidal, 5
Looking at your phone at night results in the ________________ (suppression / production) of melatonin. This results in a phase _______________ (advance / delay) of your circadian rhythm.
suppression, delay (confirm?)
what was thought of sleep historically?
that is was a state of quiet that resulted from the withdrawal of arousing input to the cortex
what did early scientists studying sleep believe?
that sleep resulted from a global reduction in neural activity or blood flow
when were our ideas of sleep revolutionized?
throughout the 19th and 20th centuries due to research
what did Ishimori, Legendre, and Pieron do?
deprived dogs of sleep, took brian extracts or CSF from these dogs and injected them into control dogs
what did Ishimori, Legendre, and Pieron find?
recipient dogs became sleepy when injected with fluids from sleep deprived dogs
recipient dogs did not become sleepy when injected with fluids from dogs that were not sleep deprived
Ishimori, Legendre, and Pieron overall findings?
there must be a chemical agent in the brain that promotes sleep, builds up during the day
what are EEGs?
electoencephalogram
what do EEGs show?
electrical activity in the brain changed throughout the cycle of waking and sleeo
what is sleep characterized by EEG?
high-amplitude, slow waves and burst of faster activity (sleep spindles)
what do EEGs show during waking?
low-amplitude, faster waves
what did Alfred Loomis do?
in 1930s made EEG recordings of people while awake and asleep
what did Loomis note from EEG study?
people transitioned through different stages of sleep, A-E, characterized by different EEG patterns
what did Loomis note about two specific sleep stages?
hard to wake people from stages D and E (deep sleep)
why is influenza relevant?
influenza viral pandemic (1918)
killed approximatley 40 million
many people who survived developed encephalitis lethargica
what did constantin von economo do?
studied the brain after death
where was insomnia localized?
posterior part of hypothalamus
where was somnolence localized?
anterior part of hypothelamus
what is there new evidence of?
that specific regions of the brain may trigger or suppress sleeo
what did frederic bremer do?
experimentally transected brainstems of cats
what happens with a lower medulla transection?
most cranial nerves still reach the brain, continued alternating cycles of electrical activity that resembled periods of wake/sleep
what happens with a midbrain transection?
cats brains could not receive input from most of the cranial nerves (sensory systems)
EEG patterns resembled those of sleep and did not regain signs of waking
what did early research on sleep seem to support? (Bremer)
the idea that cessation of sensory input to the brain results in sleep
what did magoun, moruzzi and lindsley do?
research on cats
what did magoun, moruzzi and lindsley find?
electrical stimulation of the reticular formation (specifically ARAS) triggered sustained cortical activation regardless of whether primary sensory pathways were intact or interrupted
where is the reticular formation?
brainstem
what does it mean if the reticular formation is damaged?
sensory stimulation would cause transient cortical arousal during the stimulation, but not sustained arousal
what is ARAS necessary for?
sensory stimuli to produce sustained activation of the cortex and stimulation of the ARAS alone was sufficient to produce cortical arousal, even if primary sensory projections to the cortex were absent
what does ARAS mediate?
mediates arousal to external stimuli because it is innervated by collateral fibres branching off from principle pathways that carry specific sensory info to the thalamus
who discovered REM sleep?
Kleitman and aserinsky
what did Kleitman and aserinsky do?
recorded electrical activity of eye muscles using electrodes attached to skin lateral to the eyes
how did Kleitman and aserinsky record eye movement?
electrooculogram (EOG)
what did Kleitman and aserinsky find during sleep?
slow, rolling eye movements stopped shortly after sleep onset
what are REMs?
bursts of rapid, jerky, bilaterally symmetrical eye movements
what is REM associated with?
lightening of sleep, increased breathing and heart rates
what sleep periods resemble waking?
periods with high numbers of REMs accompanied by cortical EEG patterns with rapid, low-amplitude activity
how often does REM ocur?
every 2 hours or less, three or four times during the night
what did william dement study?
humans and cats
what did dement find?
soon after falling asleep people descended from wakefulness through a series of progressively deeper non-REM (NREM) sleep stages with the first REM sleep period occurring an hour or more after sleep onset
alternating REM and NREM sleep periods in cycles just over…
90 minutes
how much does REM sleep occupy?
occupied ~20-25% of night’s sleep with longer REM sleep episodes later in the night
what did michael jouvet study?
cats
what did jouvet find?
called REM sleep paradoxical sleep because of discrepancy between EEG pattern and behaviour of cat
what did jouvet find during PS?
there was complete, sustained loss of postural muscle tone - atonia
what did jouvet attribute loss of postural muscle tone to?
descending inhibition of spinal motor systems by a region of the pons
consistent features of REM sleep?
- EEG recordings during REM sleep resembled pattern seem in awake, aroused organisms more than NREM stages of sleep
- threshold for arousal during REM sleep quite high, inconsistent with EEG pattern reflecting very light sleep or arousal
- NREM and REM sleep alternated rhythmically throughout the sleep phase
- self-reported mental activity changed with NREM and REM sleep (eg. dreams)
what did the first reports of daily rhythm involve?
the sleep movements of plants:
prayer plant and sensitive plant
what did jean-jacques d’ortous de mairin do?
placed a sensitive plant in a dark closet without access to light, noted that leaves continued to move up and down in synchrony with external day-night cycle
what did augustin pytamus de candolle do?
kept plant in constant light, daily leaf movements continued rhythmically but on a cycle of roughly 22 hours. over time the leaves’ rhythm fell out of synch with the (unseen) external cycle of day and night
what did blinded rats show about circadian rhythms?
showed robust activity rhythms in absence of external time cues, not synchronized to day-night cycle
what did fruit flies show about circadian rhythms?
rhythms persisted under constant environmental conditions
what did maynard johnson find?
period of the activity rhythms in white-footed mice changed systematically in response to changes in the intensity of the constant lighting to which they were exposed
what did johnson hint at?
hinted at a mechanism by which sleep-wake cycles can become linked to the day night cycle
who termed the coin circadian?
franz halberg
what does circadian mean?
circa = about
dian = day
what are circadian rhythms?
rhythms that express periods near 24h in length in the absence of external time cues
what are electrophysiological recordings of sleeo?
EEG, EOG, EMG
heart rate, oxygen saturation of blood, air flow through nostrils, respiratory effort, leg movements
what is the polysomnogram (PSG)?
combo of EEG, EOG, EMG and other physiological measures
what is the electroencephalogram?
EEG record is generated by amplifying and recording minute electrical signals that are the produce of activity of neurons within the brain
how does EEG placement work?
electrodes are placed on the scalp in standardized placement system
10/20 system
what are EEG changes highly correlated with?
state of sleep and waking
what do EEG recordings not look like simple sine waves?
a single electrode on the surface of the scalp is recording many neurons - often (eg. when awake) some neurons are being excited, and others are being inhibited
what kind of electrical pattern are EEGs?
desynchronized
what happens for electrical pattern to be synchronized?
when the majority of the population of neurons under an electrode are excited or inhibited at the same time, the resulting electrical pattern is synchronized
what is fourier analysis?
any complex waveform can be decomposed into a series of pure sine waves of different frequencies that are weighted differently, depending on how strongly each frequency is represented in that waveform
what do fourier analysis yield?
a power spectrum
what is a power spectrum?
plots how much power (Weighting) is associated with each pure sine wave frequency that contributes to a given waveform
highest peak = most powerful frequency
what are fourier analysis and resulting power spectrums (of EEGs) used to do?
characterize the stages of sleep
how are stages of sleep characterized?
by which EEG frequencies dominate them
what are the frequencies relevant for studying sleep?
beta, alpha, theta, delta, slow oscillations
beta waves?
> 12 Hz
alpha waves?
8-12 Hz
theta waves?
4-8 Hz
delta waves?
1-4 Hz, slow waves, voltage amplitude 75-140 µV
slow oscillations?
<1 Hz, very high amplitudes > 140 µVQW
what did Rauf et al (2013 focus on?
six paranormal beliefs and their associations with sleep quality variables, as well as isolated sleep paralysis and exploding head syndrome
where did rauf get their questions from?
four paranormal beliefs were evaluated using a sub-scale from the paranormal assesment scale, two developed by authors
response options ranged from 1 (definitely not) to 5 (definitely yes)
what is sleep efficiency?
the ratio between sleep duration and the total time dedicated to sleep in bed expressed as a percentage
how did rauf measure sleep efficiency?
using three items from pittsburg sleep quality index
how did rauf measure insomnia symptoms?
measured using items from the insomnia severity index - 1 to 5
how did rauf assess EHS and ISP?
using 11 items each adapted from the EHS interview and fearful isolated sleep interview
rauf participants?
8853 participants, classifed as 93% white, 67% female, mean age of 47 years
rauf overarching results?
people with trouble sleeping seem to believe more in paranormal activity
rauf: sleep efficiency results?
Most people with good sleep efficiency are saying they definitely do not believe in paranormal beliefs; people with poor sleep efficiency are more likely to believe in paranormal activity
rauf: sleep latency results?
People with low sleep latency (good) saying they definitely do not believe in these things and vice versa
rauf: sleep duration results?
People with longer sleep duration are less likely to believe in paranormal activities and vice versa
rauf: insomnia results?
Higher insomnia = more severe, people with less insomnia are less likely to believe in paranormal activities and vice versa
rauf: paralysis results
Belief that aliens have visited earth, of the participants that said yes experienced EHS more, same with sleep paralysis
Belief about life after death, paralysis higher with definitely yes