cortical states Flashcards
what is an ultradian and circadian cycle
ultradian: cycle shorter than one day
circadian: around 24h
types of changes that follow the circadian rhythm (3)
- physical changes
- mental changes
- behavioral changes
external cues used to distinguish night and day (2)
- daily routines (meals, social interactions)
- light and darkness
most important cues for circadian rhythm (2)
- light
- physical activity
how does light regulate circadian rhythm
sensors in retina signal changes to the brain (SCN)
what is the central/master clock
scn of the hypothalamus
how does physical activity regulate circadian rhythm
sends signals (increase in temperature and metabolism) to the peripheral clock
what is the peripheral clock
muscle tissue and other organs
how does light influence the synthesis of melatonin
photosensitive ganglion cells (melanopsin) sense light and project to scn; reach pineal gland than synthesizes melatonin
relationship bw light and melatonin
light inhibits release of melatonin
when is peak of melatonin and cortisol
melatonin: middle of night
cortisol: end of night/when wake up
what controls secretion of cortisol
scn and adrenal gland clock (central clock)
what role does cortisol play in internal clocks
plays part in synchronization of cell-autonomous clocks
cortisol secretion increases with (3)
- immune system response
- intense physical activity
- psychological and emotional stress
how does light influence mood
light takes different pathway than circadian rhythm regulation pathway to influence mood via NAc and mPFC
effects of sleep deprivation (4)
- impaired judgement
- impaired reaction times
- mood swings
- hallucinations
purposes of sleep (4)
- energy conservation
- avoid predators
- consolidation of memory
- clearance of brain metabolic waste
how does sleep help to conserve energy (2)
- replenish brain glycogen levels
- decreases metabolism
why would sleep help avoid predators
finding food and avoiding predators depends on visual information and at night, it is dark so take a break
why would sleep help consolidate memory (2)
- sleeping soon after learning increases recall
- sleep closes gate (thalamus) between STM and LTM stores
how does sleep help clear brain of metabolic waste
CSF can permeate brain during sleep and clear metabolic waste from brain
effect of closing eyes on brain waves and why
brain activity becomes synchronized because no more input from external cues (visual input)
stages of sleep
N1 -> N2 -> N3 -> R
stages in NREM sleep
N1, N2 and N3
brain waves in N1 stage
start showing lower frequency and higher amplitude
what is N1 stage
transition to sleep/drowsiness
brain waves in N2 stage
periodic bursts of activity - sleep spindles; lower frequency and higher amplitude than N1 phase
brain waves in N3 stage
slow-wave sleep (synchronization); decreased number of spindles -> delta waves
which sleep stage has delta waves
N3
brain waves in REM sleep
EEG similar to awake state
what are k complexes
spike in activity when stimulus from outside reaches brain, but doesn’t wake the person up
which sleep stage has k complexes
N2
which sleep stage has sleep spindles
N2
which sleep stage is the shortest
N3
which sleep stage is closest to awake state
REM
characteristics of REM sleep (7)
- rapid eye movement
- physiological variables increase
- pupillary constriction
- paralysis of large muscle groups (twitching of smaller muscles)
- spontaneous penile erection
- greater prevalence of dreaming
- become longer across the night
which sleep stage do dreams occur in
all stages, but mostly REM
characteristics of REM dreams (4)
- long
- primarily visual
- somewhat emotional
- not connected to immediate events of everyday life
characteristics of NREM dreams (5)
- shorter
- less visual
- less emotional
- more conceptual
- usually related to current life of dreamer
which sleeping stage decreases as we get older
at beginning of life, REM sleep decreases, but in adulthood, REM stays constant and NREM sleep decreases
which brain areas interact to form the neural circuits of sleep (3)
- brainstem (reticular activating system)
- thalamus
- cortex
what regulates the neural circuits of sleep (brainstem)
hypothalamus
states of thalamocortical neurons (2)
tonically active or intrinsic bursting state (oscillatory state)
tonically active state of thalamocortical neurons (3)
- neurons are depolarized
- sensory input (LGN, MGN)
- wakefulness - ‘gate open’ (receives input from brainstem)
oscillatory state of thalamocortical neurons (3)
- follow electrochemical properties (baseline, AP)
- synchronize with cortex
- disconnecting from outside wold - ‘gate closed’ (no input from brainstem)
what determines if the thalamus is ‘open’ or ‘closed’
brainstem nuclei
how does the thalamus act as a gate in sleep
when asleep, the thalamus is a closed gate. cortex cannot get information from the outside world which creates synchronization (only following intrinsic state)
neurotransmitters involved in sleep (3)
- noradrenaline
- acetylcholine
- serotonin
role of noradrenaline in sleep and during which state is it present
main activating NT; induces wakefulness
role of acetylcholine in sleep and during which states is it present
processes complex information and cognitive processes; present in both wakefulness and REM sleep
role of serotonin in sleep states
high quantities -> linked with wakefulness
minor quantities -> linked to NREM sleep
REM sleep (a) NT modulation, (b) activation of NT, (c) information source
(a) cholinergic
(b) high activation
(c) internal information
NREM sleep (a) NT modulation, (b) activation of NT, (c) information source
(a) serotoninergic
(b) high
(c) internal and external
awake (a) NT modulation, (b) activation of NT, (c) information source
(a) aminergic
(b) high activation
(c) external information
cholinergic, noradrenergic and serotoninergic brainstem nuclei
cholinergic -> reticular activation
noradrenergic -> locus coeruleus
serotoninergic -> raphe nuclei
NA and 5HT positively modulated by (3)
- histamine
- bupropion
- cocaine
effect of histamine on sleep
positively modulates NA and 5HT so increases wakefulness
what neurons in which nucleus inhibits wakefulness
GABAergic neurons of ventrolateral preoptic nucleus (VPLO)
effect of gaba neurons on brainstem
inhibits all ach, na and 5-ht and induces sleep
neurons responsible for NREM & REM sleep and wakefulness
NREM -> serotoninergic neurons
REM -> cholinergic neurons
awake -> noradrenergic neurons
what cells are responsible for activation of the forebrain during REM sleep
REM-ON cells (cholinergic neurons)
activity in which cortical regions increases during REM sleep and why
limbic system (like amygdala and ACC) -> high emotionality
activity in which cortical regions decreases during REM sleep and why
dlPFC and PCC -> no inhibition of impulses or inappropriate social content (ex)
why are we paralyzed in REM sleep
hyperpolarization of spinal cord motor neurons
what is the reticular activation system
group of brainstem nuclei (LC, RN and reticular)
NA + Ach + 5HT = which state?
wakefulness
low NA + high Ach = which state?
REM sleep
low NA + low Ach + high 5-HT = which state?
NREM sleep
difference bw consciousness and wakefulness
wakefulness = not asleep
consciousness = realizing what’s going on, related to attention, info reaches cortex and having part in mind (awareness)
other cortical states that aren’t awake or asleep (2)
- default mode network (daydreaming)
- central executive network (cognitive tasks)
hypothalamic nuclei that regulate brainstem and release (a) orexin, (b) histamine, (c) gaba
(a) lateral hypothalamus -> wakefulness
(b) tuberomamillary nucleus -> wakefulness
(c) ventrolateral preoptic nucleus -> sleep
why do sleep spindles occur
depolarization phase of slow oscillation; generated in thalamic circuits as a consequence of cortical firing
sleep spindles are the result of the loop of activity of which neurons (3)
- cortical pyramidal cell
- reticular cell
- thalamocortical cell
types of parasomnias (5)
- sleep walking
- sleep talking
- confusional arousals
- night terrors
- REM behavior disorder
what causes REM behavior disorder
descending inhibition of motor neurons is impaired
sleep walking, sleep talking and confusional arousals happen in which sleep stages
stage 3 and 4 (N3) - delta wave or deep sleep
eeg of parasomnias when episodes are (a) short, (b) longer
(a) eeg doesn’t change
(b) eeg looks like active state (awake or REM pattern)